Information

11.25: Introduction to Transport of Water and Solutes in Plants - Biology

11.25: Introduction to Transport of Water and Solutes in Plants - Biology


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Describe how water and solutes are transported in plants

The structure of plant roots, stems, and leaves facilitates the transport of water, nutrients, and photosynthates throughout the plant. To understand how these processes work, we must first understand the energetics of water potential.

What You’ll Learn to Do

  • Describe how water potential influences how water is transported in plants
  • Describe the process of transpiration
  • Explain how photosynthates are transported in plants

Learning Activities

The learning activities for this section include the following:

  • Water Potential
  • Transpiration
  • Photosynthates
  • Self Check: Transport of Water and Solutes in Plants

30.5 Transport of Water and Solutes in Plants

By the end of this section, you will be able to do the following:

  • Define water potential and explain how it is influenced by solutes, pressure, gravity, and the matric potential
  • Describe how water potential, evapotranspiration, and stomatal regulation influence how water is transported in plants
  • Explain how photosynthates are transported in plants

The structure of plant roots, stems, and leaves facilitates the transport of water, nutrients, and photosynthates throughout the plant. The phloem and xylem are the main tissues responsible for this movement. Water potential, evapotranspiration, and stomatal regulation influence how water and nutrients are transported in plants. To understand how these processes work, we must first understand the energetics of water potential.

Water Potential

Plants are phenomenal hydraulic engineers. Using only the basic laws of physics and the simple manipulation of potential energy, plants can move water to the top of a 116-meter-tall tree (Figure 30.31a). Plants can also use hydraulics to generate enough force to split rocks and buckle sidewalks (Figure 30.31b). Plants achieve this because of water potential.

Water potential is a measure of the potential energy in water. Plant physiologists are not interested in the energy in any one particular aqueous system, but are very interested in water movement between two systems. In practical terms, therefore, water potential is the difference in potential energy between a given water sample and pure water (at atmospheric pressure and ambient temperature). Water potential is denoted by the Greek letter ψ (psi) and is expressed in units of pressure (pressure is a form of energy) called megapascals (MPa). The potential of pure water (Ψw pure H2O ) is, by convenience of definition, designated a value of zero (even though pure water contains plenty of potential energy, that energy is ignored). Water potential values for the water in a plant root, stem, or leaf are therefore expressed relative to Ψw pure H2O .

The water potential in plant solutions is influenced by solute concentration, pressure, gravity, and factors called matrix effects. Water potential can be broken down into its individual components using the following equation:

where Ψs, Ψp, Ψg, and Ψm refer to the solute, pressure, gravity, and matric potentials, respectively. “System” can refer to the water potential of the soil water (Ψ soil ), root water (Ψ root ), stem water (Ψ stem ), leaf water (Ψ leaf ) or the water in the atmosphere (Ψ atmosphere ): whichever aqueous system is under consideration. As the individual components change, they raise or lower the total water potential of a system. When this happens, water moves to equilibrate, moving from the system or compartment with a higher water potential to the system or compartment with a lower water potential. This brings the difference in water potential between the two systems (ΔΨ) back to zero (ΔΨ = 0). Therefore, for water to move through the plant from the soil to the air (a process called transpiration), Ψ soil must be > Ψ root > Ψ stem > Ψ leaf > Ψ atmosphere .

Water only moves in response to ΔΨ, not in response to the individual components. However, because the individual components influence the total Ψsystem, by manipulating the individual components (especially Ψs), a plant can control water movement.

Solute Potential

Solute potential (Ψs), also called osmotic potential, is related to the solute concentration (in molarity). That relationship is given by the van 't Hoff equation: Ψs= –Mi RT where M is the molar concentration of the solute, i is the van 't Hoff factor (the ratio of the amount of particles in the solution to amount of formula units dissolved), R is the ideal gas constant, and T is temperature in Kelvin degrees. The solute potential is negative in a plant cell and zero in distilled water. Typical values for cell cytoplasm are –0.5 to –1.0 MPa. Solutes reduce water potential (resulting in a negative Ψw) by consuming some of the potential energy available in the water. Solute molecules can dissolve in water because water molecules can bind to them via hydrogen bonds a hydrophobic molecule like oil, which cannot bind to water, cannot go into solution. The energy in the hydrogen bonds between solute molecules and water is no longer available to do work in the system because it is tied up in the bond. In other words, the amount of available potential energy is reduced when solutes are added to an aqueous system. Thus, Ψ s decreases with increasing solute concentration. Because Ψs is one of the four components of Ψsystem or Ψtotal, a decrease in Ψs will cause a decrease in Ψtotal. The internal water potential of a plant cell is more negative than pure water because of the cytoplasm’s high solute content (Figure 30.32). Because of this difference in water potential water will move from the soil into a plant’s root cells via the process of osmosis. This is why solute potential is sometimes called osmotic potential.

Plant cells can metabolically manipulate Ψs (and by extension, Ψtotal) by adding or removing solute molecules. Therefore, plants have control over Ψtotal via their ability to exert metabolic control over Ψs.

Visual Connection

Positive water potential is placed on the left side of the tube by increasing Ψp such that the water level rises on the right side. Could you equalize the water level on each side of the tube by adding solute, and if so, how?

Pressure Potential

Pressure potential (Ψp), also called turgor potential, may be positive or negative (Figure 30.32). Because pressure is an expression of energy, the higher the pressure, the more potential energy in a system, and vice versa. Therefore, a positive Ψp (compression) increases Ψtotal, and a negative Ψp (tension) decreases Ψtotal. Positive pressure inside cells is contained by the cell wall, producing turgor pressure. Pressure potentials are typically around 0.6–0.8 MPa, but can reach as high as 1.5 MPa in a well-watered plant. A Ψp of 1.5 MPa equates to 210 pounds per square inch (1.5 MPa x 140 lb/in -2 MPa -1 = 210 lb/in -2 ). As a comparison, most automobile tires are kept at a pressure of 30–34 psi. An example of the effect of turgor pressure is the wilting of leaves and their restoration after the plant has been watered (Figure 30.33). Water is lost from the leaves via transpiration (approaching Ψp = 0 MPa at the wilting point) and restored by uptake via the roots.

A plant can manipulate Ψp via its ability to manipulate Ψs and by the process of osmosis. If a plant cell increases the cytoplasmic solute concentration, Ψs will decline, Ψtotal will decline, the ΔΨ between the cell and the surrounding tissue will decline, water will move into the cell by osmosis, and Ψp will increase. Ψp is also under indirect plant control via the opening and closing of stomata. Stomatal openings allow water to evaporate from the leaf, reducing Ψp and Ψtotal of the leaf and increasing Ψ between the water in the leaf and the petiole, thereby allowing water to flow from the petiole into the leaf.

Gravity Potential

Gravity potential (Ψg) is always negative to zero in a plant with no height. It always removes or consumes potential energy from the system. The force of gravity pulls water downwards to the soil, reducing the total amount of potential energy in the water in the plant (Ψtotal). The taller the plant, the taller the water column, and the more influential Ψg becomes. On a cellular scale and in short plants, this effect is negligible and easily ignored. However, over the height of a tall tree like a giant coastal redwood, the gravitational pull of –0.1 MPa m -1 is equivalent to an extra 1 MPa of resistance that must be overcome for water to reach the leaves of the tallest trees. Plants are unable to manipulate Ψg.

Matric Potential

Matric potential (Ψm) is always negative to zero. In a dry system, it can be as low as –2 MPa in a dry seed, and it is zero in a water-saturated system. The binding of water to a matrix always removes or consumes potential energy from the system. Ψm is similar to solute potential because it involves tying up the energy in an aqueous system by forming hydrogen bonds between the water and some other component. However, in solute potential, the other components are soluble, hydrophilic solute molecules, whereas in Ψm, the other components are insoluble, hydrophilic molecules of the plant cell wall. Every plant cell has a cellulosic cell wall and the cellulose in the cell walls is hydrophilic, producing a matrix for adhesion of water: hence the name matric potential. Ψm is very large (negative) in dry tissues such as seeds or drought-affected soils. However, it quickly goes to zero as the seed takes up water or the soil hydrates. Ψm cannot be manipulated by the plant and is typically ignored in well-watered roots, stems, and leaves.

Movement of Water and Minerals in the Xylem

Solutes, pressure, gravity, and matric potential are all important for the transport of water in plants. Water moves from an area of higher total water potential (higher Gibbs free energy) to an area of lower total water potential. Gibbs free energy is the energy associated with a chemical reaction that can be used to do work. This is expressed as ΔΨ.

Transpiration is the loss of water from the plant through evaporation at the leaf surface. It is the main driver of water movement in the xylem. Transpiration is caused by the evaporation of water at the leaf–atmosphere interface it creates negative pressure (tension) equivalent to –2 MPa at the leaf surface. This value varies greatly depending on the vapor pressure deficit, which can be negligible at high relative humidity (RH) and substantial at low RH. Water from the roots is pulled up by this tension. At night, when stomata shut and transpiration stops, the water is held in the stem and leaf by the adhesion of water to the cell walls of the xylem vessels and tracheids, and the cohesion of water molecules to each other. This is called the cohesion–tension theory of sap ascent.

Inside the leaf at the cellular level, water on the surface of mesophyll cells saturates the cellulose microfibrils of the primary cell wall. The leaf contains many large intercellular air spaces for the exchange of oxygen for carbon dioxide, which is required for photosynthesis. The wet cell wall is exposed to this leaf internal air space, and the water on the surface of the cells evaporates into the air spaces, decreasing the thin film on the surface of the mesophyll cells. This decrease creates a greater tension on the water in the mesophyll cells (Figure 30.34), thereby increasing the pull on the water in the xylem vessels. The xylem vessels and tracheids are structurally adapted to cope with large changes in pressure. Rings in the vessels maintain their tubular shape, much like the rings on a vacuum cleaner hose keep the hose open while it is under pressure. Small perforations between vessel elements reduce the number and size of gas bubbles that can form via a process called cavitation. The formation of gas bubbles in xylem interrupts the continuous stream of water from the base to the top of the plant, causing a break termed an embolism in the flow of xylem sap. The taller the tree, the greater the tension forces needed to pull water, and the more cavitation events. In larger trees, the resulting embolisms can plug xylem vessels, making them nonfunctional.

Visual Connection

Which of the following statements is false?

  1. Negative water potential draws water into the root hairs. Cohesion and adhesion draw water up the xylem. Transpiration draws water from the leaf.
  2. Negative water potential draws water into the root hairs. Cohesion and adhesion draw water up the phloem. Transpiration draws water from the leaf.
  3. Water potential decreases from the roots to the top of the plant.
  4. Water enters the plants through root hairs and exits through stoma.

Transpiration —the loss of water vapor to the atmosphere through stomata—is a passive process, meaning that metabolic energy in the form of ATP is not required for water movement. The energy driving transpiration is the difference in energy between the water in the soil and the water in the atmosphere. However, transpiration is tightly controlled.

Control of Transpiration

The atmosphere to which the leaf is exposed drives transpiration, but also causes massive water loss from the plant. Up to 90 percent of the water taken up by roots may be lost through transpiration.

Leaves are covered by a waxy cuticle on the outer surface that prevents the loss of water. Regulation of transpiration, therefore, is achieved primarily through the opening and closing of stomata on the leaf surface. Stomata are surrounded by two specialized cells called guard cells, which open and close in response to environmental cues such as light intensity and quality, leaf water status, and carbon dioxide concentrations. Stomata must open to allow air containing carbon dioxide and oxygen to diffuse into the leaf for photosynthesis and respiration. When stomata are open, however, water vapor is lost to the external environment, increasing the rate of transpiration. Therefore, plants must maintain a balance between efficient photosynthesis and water loss.

Plants have evolved over time to adapt to their local environment and reduce transpiration (Figure 30.35). Desert plant (xerophytes) and plants that grow on other plants (epiphytes) have limited access to water. Such plants usually have a much thicker waxy cuticle than those growing in more moderate, well-watered environments (mesophytes). Aquatic plants (hydrophytes) also have their own set of anatomical and morphological leaf adaptations.

Xerophytes and epiphytes often have a thick covering of trichomes or of stomata that are sunken below the leaf’s surface. Trichomes are specialized hair-like epidermal cells that secrete oils and substances. These adaptations impede air flow across the stomatal pore and reduce transpiration. Multiple epidermal layers are also commonly found in these types of plants.

Transportation of Photosynthates in the Phloem

Plants need an energy source to grow. In seeds and bulbs, food is stored in polymers (such as starch) that are converted by metabolic processes into sucrose for newly developing plants. Once green shoots and leaves are growing, plants are able to produce their own food by photosynthesizing. The products of photosynthesis are called photosynthates, which are usually in the form of simple sugars such as sucrose.

Structures that produce photosynthates for the growing plant are referred to as sources . Sugars produced in sources, such as leaves, need to be delivered to growing parts of the plant via the phloem in a process called translocation . The points of sugar delivery, such as roots, young shoots, and developing seeds, are called sinks . Seeds, tubers, and bulbs can be either a source or a sink, depending on the plant’s stage of development and the season.

The products from the source are usually translocated to the nearest sink through the phloem. For example, the highest leaves will send photosynthates upward to the growing shoot tip, whereas lower leaves will direct photosynthates downward to the roots. Intermediate leaves will send products in both directions, unlike the flow in the xylem, which is always unidirectional (soil to leaf to atmosphere). The pattern of photosynthate flow changes as the plant grows and develops. Photosynthates are directed primarily to the roots early on, to shoots and leaves during vegetative growth, and to seeds and fruits during reproductive development. They are also directed to tubers for storage.

Translocation: Transport from Source to Sink

Photosynthates, such as sucrose, are produced in the mesophyll cells of photosynthesizing leaves. From there they are translocated through the phloem to where they are used or stored. Mesophyll cells are connected by cytoplasmic channels called plasmodesmata. Photosynthates move through these channels to reach phloem sieve-tube elements (STEs) in the vascular bundles. From the mesophyll cells, the photosynthates are loaded into the phloem STEs. The sucrose is actively transported against its concentration gradient (a process requiring ATP) into the phloem cells using the electrochemical potential of the proton gradient. This is coupled to the uptake of sucrose with a carrier protein called the sucrose-H + symporter.

Phloem STEs have reduced cytoplasmic contents, and are connected by a sieve plate with pores that allow for pressure-driven bulk flow, or translocation, of phloem sap. Companion cells are associated with STEs. They assist with metabolic activities and produce energy for the STEs (Figure 30.36).

Once in the phloem, the photosynthates are translocated to the closest sink. Phloem sap is an aqueous solution that contains up to 30 percent sugar, minerals, amino acids, and plant growth regulators. The high percentage of sugar decreases Ψs, which decreases the total water potential and causes water to move by osmosis from the adjacent xylem into the phloem tubes, thereby increasing pressure. This increase in total water potential causes the bulk flow of phloem from source to sink (Figure 30.37). Sucrose concentration in the sink cells is lower than in the phloem STEs because the sink sucrose has been metabolized for growth, or converted to starch for storage or other polymers, such as cellulose, for structural integrity. Unloading at the sink end of the phloem tube occurs by either diffusion or active transport of sucrose molecules from an area of high concentration to one of low concentration. Water diffuses from the phloem by osmosis and is then transpired or recycled via the xylem back into the phloem sap.


Movement of Water Molecules

Water moves from areas of where water potential is higher (or less negative), to areas where it is lower (or more negative), and we refer to this movement as osmosis. For example, in the diagram below, the solution around the cell is hypertonic, meaning that it has a higher concentration of solute, so a lower water potential, than the inside of the cell. Since the cell has a partially-permeable membrane, allowing the movement of water in and out of it, water will move from inside of the cell, where Ψ is higher, to outside of the cell, where Ψ is lower. This can lead to the death of cells in living organisms. On the other hand, a cell that is placed in a pure water solution could take up water until it bursts and dies. Therefore, cells need an environment that does not differ significantly in its solute concentrations.

Water potential is what allows water to get into plant roots when there is more solute within the root cells than the water in the soil. And as we go up the plant, Ψ decreases more and more, drawing water into the stems and then the leaves, which constantly get water evaporated out of them, maintaining a high solute concentration and a low Ψ. In our bodies, solute concentration is regulated through osmoregulation, which controls and maintains water and salt concentrations to keep us alive.


Water and Plant Life (With Diagram)

Water (H2O) is normal oxide of hydrogen in which the two hydrogen atoms are joined to oxygen atom by covalent bonds forming an angle of 105° (Fig. 2.1 A). Since, oxygen atom is more electronegative than hydrogen atom the electrons of the covalent bonds tend to be at­tracted towards oxygen atom. This results in partial negative charge (δ – ) on oxygen and equal partial positive charges (δ + ) on each hydrogen in water molecule. Because the partial negative and positive charges are equal, water molecule carries no net charge and is neutral.

However, partial negative and positive charges on two sides of water molecule make it a polar molecule with the result that positive side of one water molecule is attracted towards negative side of another water molecule forming a weak electro static chemical bond between the polar water molecules which is called as a hydrogen bond and is represented by dotted line (Fig. 2.1 B). The hydrogen bonds present in between the water molecules provide water with unique physi­cal properties.

Hydrogen bond is a weak electrostatic chemical bond formed between covalently bonded hydrogen atom and a strongly electronegative atom with a lone pair of electrons such as nitro­gen or oxygen and is represented by dotted line. The energy of hydrogen bond is lesser than ionic or covalent bond but higher than Van der Waals forces and it varies from 8-42 kilojules/ mols of bonds (kJ mol – ‘).

In plants, hydrogen bonds may also be formed between water and other substances espe­cially those which contain electronegative O or N atom with lone pairs of electrons. The hydrogen bonds are of tremendous biological importance, especially the N-H…N bond that enables complex proteins and nucleic acids to be built up.

Physical Properties of Water:

Natural water (rain, spring, river etc.) is never pure and contains dissolved substances in it. However, pure water is colourless, odorless liquid with mol. wt. 18 Dalton, m.p. 0°C, b.p. 100°C and maximum density of 1 gm. per cm 3 at 4°C.

Specific Heat:

The amount of heat energy required to raise the temperature of unit mass of a substance 1°C is called as specific heat. For 1 gm. of pure water, this value is 1 calorie (4.184 joules). The specific heat of water is higher than other liquids (except liquid ammonia).

It is due to the presence of hydrogen bonds between water molecules. When temp, of water is raised, the water molecules vibrate faster and absorb large quantities of energy to break the hydrogen bonds. Therefore, relatively large input of energy is required to raise its temp, in comparison to other liquids. The high specific heat of water is of great importance to plants in protecting them from potentially harmful temperature fluctuations.

Latent Heat of Vaporization:

It is the energy required to convert liquid into gas (vapour) phase at constant tempera­ture. For water, the latent heat of vaporization is 44 kJ mol -1 at 25°C and is highest known value among all the liquids. Most of this energy is needed to break the hydrogen bonds be­tween water molecules. The higher latent heat of vaporization of water enables the plants to cool themselves by dissipating heat through foliar transpiration.

Latent Heat of Fusion:

It is the heat energy required to convert unit mass of a solid to a liquid at the same tem­perature. To melt 1 gm of ice at 0°C, 80 Cal. (335 J) of energy is needed which again is a very high value caused due to the presence of hydrogen bonds, even though ice has fewer hydro­gen bonds per molecule than liquid water. In ice, each water molecule is joined to four others by H-bonds, forming a tetrahydral structure (Fig. 2.1 C). The tetrahydrons are arranged in such a way that ice crystals are basi­cally hexagonal.

When ice melts to liquid water, the water molecules move farther apart. However, it is noteworthy that its volume actually decreases during melting. The reason lies in the fact that water molecules are more efficiently packed in liquid water than in ice. In water, each molecule is joined to 5 or more others by H-bonds.

Water Expansion and Density:

Water has a tendency to expand as it freezes and its density is decreased. Therefore, ice has lower density than water and it floats on top of oceans, lakes, rivers etc. in winters and provides a shield to life forms growing underneath it. On cooling, water reaches is maximum density of 0.999973 gm/cm 3 at 3.98°C (or app 1 gm/cm at 4°C). Water expands as the temp, falls to 0°C. Its density at 0°C being 0.999841 gm/cm 3 . When water freezes, it expands still further forming ice with a density of 0.9168 gm/cm 3 at 0°C. This expansion of water in freezing temperatures often causes bursting of water pipes in winters.

Cohesive and Adhesive Properties:

Mutual force of attraction between like molecules such as in water (due to H-bonds) is called as cohesion. On the other hand, attraction of water to a solid phase such as cell wall or glass surface is called as adhesion. Cohesive and adhesive properties of water are of great significance in ascent of sap in plants.

Surface Tension:

Surface tension results due to forces of attraction existing between the molecules of a liquid at the open boundary surface of that liquid and is measured by the force per unit length (newton/metre) acting in the surface at right angle to any line drawn in the surface.

With reference to water, the water molecules at the air-water interface are continuously being pulled into liquid due to cohesion than to the gas (vapour) phase on the other side of the surface. This unequal attraction of water molecules tends to minimise surface area at air- water interface and exerts a force or surface tension on the latter.

The surface tension of water is relatively higher than most of other liquid (except hydra­zine and most metals in liquid state such as mercury). Surface tension is responsible for ‘tran­spiration pull’ that facilitates ascent of sap in higher plants.

Tensile Strength:

It is the ability to resist pulling without breaking and is measured as force per unit area e.g., newton’s per square metre of dynes per square centimetre. Cohesion of water molecules gives water a high tensile strength which enables water column in xylem elements of stem to be pulled to the top of tall trees without breaking.

Water as a Solvent:

The polarity of water makes it an excellent solvent. Water dissolves greater amounts and wider variety of substances than any other common solvent. Water is especially powerful solvent for electrolytes and other substances such as sugars, proteins etc. which have polar -OH or -NH2 groups. Water forms a shield around charged ions or charged surface of sol­vents due to its polar nature, thereby decreasing the electrostatic interaction between charged substances and increasing their solubility.

Importance of Water to Plant Life:

Life is unconceivable without water and plants are no exceptions. Water constitutes 80-95% of the total weight of growing plant tissues. The seeds which are driest plant tissues still contain 5-15% water content and must absorb considerable amount of water before they ger­minate.

i. Water is best known solvent and provides medium for the movement of molecules within and in between the cells.

ii. Almost all molecules of protoplasm owe their specific biochemical activities to water environment (milieu) in which they exist.

iii. The structures of macromolecules such as proteins, nucleic acids, polysaccharides and other cell constituents are greatly influenced by water.

iv. Water takes direct part in many biochemical reactions in the cells such as hydroly­sis, hydration, and dehydration. Water is also one of the raw materials in photosynthesis.

v. Through transpiration, water plays an important role in controlling temperature of plants.

vi. Contrary to animals, the plant cells contain large central vacuole filled with cell sap and develop large intracellular pressure called as turgor pressure.

Turgor pressure is es­sential for many physiological processes in plants such as:

iii. Transport of solutes in phloem,

iv. Transport processes in cell membranes,

v. Maintaining shape or form of the plant tissues,

vi. Emergence of young seedling from the soil etc.

vii. Water is most important factor for agricultural productivity.

viii. Water is an essential factor in completing the life cycles of lower forms of plant life and aquatic higher plants.


Plant &ndash Absorption, Conduction, Rise of Cell Sap & Transportation

All plants need water, minerals and food. There is a system present in plants called transport system to distribute these substances throughout the body.

Flowering plants have a very well developed system to transport these substances, this system is called vascular system. Vascular system contains two types of tissues, xylem and phloem.

Xylem distributes water and phloem distributes food throughout the plants body. Plants need water for photosynthesis, transpiration, transportation and for mechanical function. Minerals are also required by the plants as salts or as ions. Water is absorbed by the roots, [Fig. 2.1 (a)] for this, roots provide huge surface area, they contain cell sap of higher concentration than the surrounding water and root hair have thin walls. The vascular tissues are present in plant body from the tip of roots up to the leaves, xylem and phloem also joined end to end and form long tubes and phloem cells form long tubes for their functions.

Absorption of Water:

Water enters the plant body through root hair, by the process of osmosis. Osmosis is a process by which the molecules of solvent (water) move from a region of low concentration to a region of high concentration through a semi permeable membrane.

Demonstration of Osmosis using Potato Osmoscope:

Scoop a cavity in a large sized peeled potato, now slice the bottom to make the base flat. Now this potato is kept in water containing petri-dish, in such a way that half potato is immersed in water. Now fill the potato cavity with 25% sucrose solution and mark its level by inserting a pin (As show in diagram) Fig. 2.2.

Now after some time, we observe that liquid in cavity rises, because, the water (pure solvent) has moved through the potato walls and accumulated inside the cavity, when concentration of water molecules (solvent) was lower (due to the presence of sucrose molecules). This experiment proves that osmosis has taken place. Potato wall acts as semi permeable membrane but if we boil the potato the membrane loses its semipermeable nature and only diffusion will take place.

Diffusion is the movement of molecules of a substance from a region of higher concentration to a region of lower concentration:

Demonstration of Osmosis by using thistle funnel:

Close the mouth of thistle funnel by parchment paper and now fill thistle funnel by sugar solution and suspend the thistle funnel in beaker containing water. (Fig. 2.3a) After one or two hours level of solution in the stem of thistle funnel rises due to the movement of water molecules in thistle funnel through parchment paper, which act as semi-permeable membrane.

This proves that the water molecules move from low concentration (from beaker) to the high concentration (inside thistle funnel) say osmosis. (Fig. 2.3 b).

[Fig. 2.1 (b)] root hair cells have high concentration or osmotic pressure, as compared to surrounding water due to this water diffuses from outside into the root cells. In roots most absorption takes place by root hair zone having numerous root hairs. The walls of root hair are very thin and permeable.

The absorption of water by the solid particles of a substance in dry or semi-dry condition with forming a solution is called imbibition. Absorption also takes place by diffusion and osmosis. Through these processes molecules of substances move from higher concentration to lower concentration. Water molecules also move through semi-permeable membrane from a dilute to concentrated solution.

Experiment to show absorption of water:

Put a young leafy plant in a water containing test tube (Fig. 2.4). Put some oil drops to prevent evaporation. Mark the level of water. After some time you will see that water level has gone down. It proves that water lost was absorbed by the roots.

Vascular bundles in stem, roots, leaf veins forms an unbroken system of tubes which collectively perform a transport system (Fig. 2.5) throughout the entire plant body. Water and salts travel upwards through xylem tissues and food travels up and down directions through phloem tissues (Fig. 2.6 a & b).

Conduction of water through xylem:

Cut two leafy shoots of balsam plant (Fig. 2.7) under water to prevent entry of any air bubble. Now by keeping lower end of shoot in water remove near about 2-3 cm outer ring (phloem) of stem, keeping the central part intact. In second shoot, remove the central part (xylem) of equal length. Now fix both the shoots in stands and observe, after two days we find that the leaves of first shoot remain turgid and stands normally, but in second twig leaves wilt and droop down, this experiment proves that water is conducted through xylem.

Conduction of food through phloem:

Cut a ring around the stem of a healthy plant deep enough to penetrate the phloem and cambium but not the xylem. It will be seen that sap starts oozing out from the farther cut-margin of the stem. After some weeks, it is seen that part of the stem above the ring has grown in diameter and below the ring the growth of stem is stopped and may die after some time, when food stored is finished. The leaves are healthy due to continuous supply of water through the xylem tissues.

Rise of cell sap:

The upward movement of water with dissolved minerals from roots to the tips of stem, branches and their leaves is called ascent of sap (Fig. 2.8). The water along with dissolved minerals is absorbed by the root hairs of the roots from the soil. The sap absorbed by the root hairs passes through the cortex, pericycle of roots to enter the elements of xylem (vessels, tracheids and xylem parenchyma). This movement of sap takes place by two ways, one is by active transportation which requires energy and other is by transpiration pull.

The loss of water in the form of water vapours from the aerial parts of a plant is called transpiration.

Types of transpiration:

1. Stomatal transpiration:

Evaporation of water from the leaves taking place through the stomata, is called stomatal transpiration.

2. Cuticular transpiration:

When the evaporation of water takes place directly from the surface of the leaves and herbaceous stems, it is known as cuticular transpiration.

3. Lenticular and bark transpiration:

When evaporation of water takes place through the lenticels and the bark, it is called lenticular and bark transpiration.

Experiment on transpiration:

Take a potted plant and cover the soil surface in the pot with a rubber or polythene sheet (Fig. 2.9).

Now potted plant is placed on a glass plate and a bell jar is put over the potted plant to cover it and to make it air tight. After sometime, it is observed that the inner walls of the bell jar are covered with moisture. The moisture has come through transpiration.

Factors affecting Transpiration:

1. Transpiration is more rapid in bright light than in diffuse light or in darkness.

2. At high temperature, the rate of transpiration is increased.

3. Moving air current increases the rate of transpiration, but due to high velocities of wind the rate of transpiration is decreased as it leads to stomatal closure.

4. The thickness of the cuticle and the number of stomata affect the rate of transpiration.

5. High humidity in the air reduces the rate of transpiration, as the rate of outward diffusion of internal water vapours across stomata is reduced.

6. Rate of transpiration increases with the decrease in atmospheric pressure.

7. Increase in the carbon dioxide level in the outside air over normal 0.03% causes stomal closure and results in the decrease of transpiration.

8. If water content of leaves decreases due to less absorption of water by the roots the leaves wilt and transpiration is reduced.

Importance of Transpiration:

1. Transpiration leads to the concentration of sap in the plant cells, which helps in osmosis.

2. Transpiration has a cooling effect on the plant.

3. Salts move upwards in the plant due to transpiration.

4. Through transpiration, plants expel out excess water absorbed by the roots, but excessive transpiration may cause wilting and death of the plant.

More transpiration occurs from the under surface of a leaf:

There are more stomata present on the under surface of a dicot leaf, therefore more transpiration takes place from the under surface of the leaf. To prove this, we conduct an experiment by putting cobalt chloride paper on both the surfaces of leaf with the help of clips properly, after some time we observe that cobalt chloride paper (Fig. 2.10) of upper surface either does turn pink than the lower surface which turns pink more quickly. This proves that more transpiration occurs from the lower surface of leaf.


The Difference Between Apoplast and Symplast

Apoplast refers to the non protoplasmic components of a plant, including the cell wall and the intracellular spaces.

Symplast refers to the continuous arrangement of protoplasts of a plant, which are interconnected by plasmodesmata.

Apoplast consists of non protoplasmic parts such as cell wall and intracellular space.

Symplast Consists of protoplast

Apoplast composed of nonliving parts of a plant.

Symplast composed of living parts of a plant.

In apoplast, the water movement occurs by passive diffusion.

In symplast, the water movement occurs by osmosis.

In apoplast, the water movement is rapid.

In the symplast, the water movement is slower.

The metabolic rate of the cells in the root cortex does not affect the water movement.

The metabolic rate of the cells in the root cortex highly affects the water movement.

It shows less resistance to the water movement.

It shows some resistance to the water movement.

With the secondary growth of the root, most of the water moves by the apoplast route.

Beyond the cortex, water moves through the symplast route.

Similarities Between Apoplast and Symplast:

Apoplast and symplast are two ways in which the water moves from root hair cells to the xylem.

Both the apoplast and symplast occur in the root cortex.

Both the apoplast and symplast carry water and nutrients towards the xylem.

Pathways For Root Absorption Through Apoplast:

The apoplastic pathway provides a way towards the vascular cell through free spaces and cell walls of the epidermis and cortex. An additional apoplastic route that allows the direct access to the xylem and phloem is along the margins of the secondary roots. The secondary root is developed from the pericycle, a cell layer just inside the endodermis. The endodermis is characterized by the Casparian strip. Apoplast was previously defined as the whole thing but the symplast, consisting of cell walls and spaces between cells in which water and solutes can move freely.


Phloem Loading and Unloading in Plants

Translocation of organic solutes such as sucrose (i.e., photosynthetic) takes place through sieve tube elements of phloem from supply end (or source) to consumption end (or sink). But, before this translocation of sugars could proceed, the soluble sugars must be transferred from mesophyll cells to sieve tube elements of the respective leaves.

This transfer of sugars (photosynthetic) from mesophyll cells to sieve tube elements in the leaf is called as phloem loading. On the other hand, the transfer of sugars (photosynthetic) from sieve tube elements to the receiver cells of consumption end (i.e., sink or­gans) is called as phloem unloading. Both are energy requiring processes.

Phloem Loading:

As a result of photosynthesis, the sugars such as sucrose produced in mesophyll cells move to the sieve tubes of smallest veins of the leaf either directly or through only 2-3 cells depending upon the leaf anatomy. Consequently, the concentration of sugars increases in sieve tubes in comparison to the surrounding mesophyll cells.

The movement of sugars from mesophyll cells to sieve tubes of phloem may occur either through symplast (i.e., cell to cell through plasmodesmata, remaining in the cytoplasm) or the sugars may enter the apoplast (i.e., cell walls outside the protoplasts) at some point en route to phloem sieve tubes.

In the latter case, the sugars are actively loaded from apoplast to sieve tubes by an energy driven transport located in the plasma membrane of these cells. The mechanism of phloem loading in such case has been called as sucrose-H + symport or cotransport mechanism.

According to this mechanism (Fig. 15.5 ) protons (H + ) are pumped out through the plasma membrane using the energy from ATP and an ATPase carrier en­zyme, so that concentration of H + becomes higher outside (in the apoplast) than inside the cell. Spontaneous tendency toward equilibrium causes protons to diffuse back into the cyto­plasm through plasma membrane coupled with transport of sucrose from apoplast to cyto­plasm through sucrose -H + symporter located in the plasma membrane.

The mechanism of the transfer of sugars (sucrose) from mesophyll cells to apoplast is however, not known.

Phloem loading is specific and selective for transport sugars. Both symplastic and apoplastic pathways of phloem loading are used in plants but in different species. In some species however, phloem loading may occur through both the path­ways in the same sieve tube element or in different sieve tube elements of the same vein or in sieve tubes in veins of different sizes.

Experimental findings have revealed certain patterns in apoplastic and symplastic load­ing of sugars in phloem (Table 15.1), which appears to be related with the type of sugar transported to phloem, type of companion cells (ordinary, transfer or intermediary) and num­ber of plasmodesmata (few or abundant ) connecting the sieve tubes (including the com­panion cells) to surrounding cells in smaller veins.

To some extent, phloem loading is also correlated with the family of plant, its habit (trees, shrubs, vines or herbs) and climate such as temperate, tropical or arid climate.

Phloem Unloading:

It occurs in the consumption end or sinks organs (such as developing roots, tubers, reproductive structures etc.)

Sugars move from sieve tubes to receiver cells in the sink in­volving following steps:

(i) Sieve element unloading:

In this process, sugars (imported from the source) leave sieve elements of sink tissues.

(ii) Short distance transport:

The sugars are now transported to cells in sink by a short distance pathway which has also been called as post-sieve element transport.

(iii) Storage and metabolism:

Finally, sugars are stored or metabolized in the cells of the sink.

As with the phloem loading process, sucrose unloading also occurs through symplast via plasmodesmata or through apoplast at some point en route to sink cells.

Phloem unloading is typically symplastic in growing and respiring sinks such as meristems roots, and young leaves etc. in which sucrose can be rapidly metabolized. (Young leaves act as sink until their photosynthetic machinery is fully developed, at which point they become sources).

Usually, in storage organs such as fruits (grape, orange etc.), roots (sugar beet) and stems (sugarcane), sucrose unloading is known to occur through apoplast. However, according to Oparka (1986), phloem unloading in potato tubers from sieve elements to cortical cells is a symplastic passive process. Because, there are wide varieties of sinks in plants which differ in structure and func­tion, no one scheme of phloem unloading is available.

Related Articles:

Welcome to BiologyDiscussion! Our mission is to provide an online platform to help students to share notes in Biology. This website includes study notes, research papers, essays, articles and other allied information submitted by visitors like YOU.

Before sharing your knowledge on this site, please read the following pages:

Questions

About Us

Suggestions

New Questions and Answers and Forum Categories

This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Answer Now and help others.


Staining Science: Capillary Action of Dyed Water in Plants

Introduction
Have you ever heard someone say, "That plant is thirsty," or "Give that plant a drink of water."? We know that all plants need water to survive, even bouquets of cut flowers and plants living in deserts. But have you ever thought about how water moves within the plant? In this activity, you'll put carnations in dyed water to figure out where the water goes. Where do you think the dyed water will travel, and what will this tell you about how the water moves in the cut flowers?

Background
Plants use water to keep their roots, stems, leaves and flowers healthy as well as prevent them from drying and wilting. The water is also used to carry dissolved nutrients throughout the plant.

Most of the time, plants get their water from the ground. This means it has to transport the water from its roots up and throughout the rest of the plant. How does it do this? Water moves through the plant by means of capillary action. Capillary action occurs when the forces binding a liquid together (cohesion and surface tension) and the forces attracting that bound liquid to another surface (adhesion) are greater than the force of gravity. Through these binding and surface forces, the plant's stem basically sucks up water&mdashalmost like drinking through a straw!

A simple way of observing capillary action is to take a teaspoon of water and gently pour it in a pool on a countertop. You'll notice that the water stays together in the pool, rather than flattening out across the countertop. (This happens because of cohesion and surface tension.) Now gently dip the corner of a paper towel in the pool of water. The water adheres to the paper and "climbs" up the paper towel. This is called capillary action.

Materials
&bull Water
&bull Measuring cup
&bull Glass cup or vase
&bull Blue or red food color
&bull Several white carnations (at least three). Tip: Fresher flowers work better than older ones
&bull Knife
&bull Camera (optional)

Preparation
&bull Measure a half cup of water and pour it into the glass or vase.
&bull Add 20 drops of food color to the water in the glass.
&bull With the help of an adult, use a knife to cut the bottom stem tips of several (at least three) white carnations at a 45-degree angle. Tip: Be sure not to use scissors, they will crush the stems, reducing their ability to absorb water. Also, shorter stems work better than longer ones.
&bull Place the carnations in the dyed water. As you do this, use the stems of the carnations to stir the water until the dye has fully dissolved.

Procedure
&bull Observe the flowers immediately after you put them in the water. If you have a camera, take a picture of the flowers.
&bull Observe the flowers two, four, 24, 48 and 72 hours after you put them in the dyed water. Be sure to also observe their stems, especially the bumps where the leaves branch from the stem and it is lighter green (it may be easier to see the dye here). If you have a camera, take pictures of the flowers and stems at these time points.
&bull How did the flowers look after two hours? What about after four, 24, 48 and 72 hours? How did their appearance change over this time period?
&bull What does the flowers' change in appearance tell you about how water moves through them?
&bull Extra: In this activity, you used carnations, but do you think you'd see the same results with other flowers and plants? Try this activity with another white flower&mdash a daisy, for instance&mdashor a plant that is mostly stem, such as a stalk of celery.
&bull Extra: Try doing this activity again but use higher or lower concentrations of food color, such as one half, twice, four times or 10 times as much be sure to mix each dye amount with the same amount of water. What happens if you increase or decrease the concentration of food color in the water?
&bull Extra: How would you make a multicolor carnation? Tip: You could try (1) leaving the flower for a day in one color of water and then putting it in another color of water for a second day or (2) splitting the end of the stem in two and immersing each half in a different color of water.


Observations and results
When you put the flowers in the dyed water, did you see some of the flowers start to show spots of dye after two hours? Did you also see some dye in the stems? After 24 hours did the flowers overall have a colored hue to them? Did this hue become more pronounced, or darker, after 48 and 72 hours?

Water moves through the plant by means of capillary action. Specifically, the water is pulled through the stem and then makes its way up to the flower. After two hours of being in the dyed water, some flowers should have clearly showed dyed spots near the edges of their petals. The water that has been pulled up undergoes a process called transpiration, which is when the water from leaves and flower petals evaporates. However, the dye it brought along doesn't evaporate, and stays around to color the flower. The loss of water generates low water pressure in the leaves and petals, causing more colored water to be pulled through the stem. By 24 hours the flowers should have gained an overall dyed hue, which darkened a little over time. The stems should have also become slightly dyed in places, particularly where the leaves branch off.

More to explore
Plant Parts: What Do Different Plant Parts Do? from Missouri Botanical Garden
Capillary action from The U.S. Geological Survey, Water Science School
The Water Cycle: Transpiration from The USGS Water Science School
Transpiration in Plants from TutorVista.com
Suck It Up: Capillary Action of Water in Plants from Science Buddies

This activity brought to you in partnership with Science Buddies


Transport of Nutrients in Plants

Transport of Nutrients in Plants provides the study of nutrient movement in plants. The greater part of this book deals with the physiology and cytology of phloem. The first chapter of the text deals with studies on the definition of the cellular pathways of transport. Chapter 2 considers how the mobility of solutes can be measured and the range of chemical species which are moved in xylem and phloem. The next chapter discusses the concepts of velocity and rate. The rest of the book is devoted to the characteristics of phloem transport and the ultrastructure of sieve elements, including such topics as the control of movement, solute-loading and -unloading mechanisms, the dependence of transport upon metabolic energy, bidirectional movement and water movement in phloem. Finally an account is given of the movement of endogenous growth regulators and a brief assessment of 'hormone-directed' transport. Botanists will find the book very interesting and informative.

Transport of Nutrients in Plants provides the study of nutrient movement in plants. The greater part of this book deals with the physiology and cytology of phloem. The first chapter of the text deals with studies on the definition of the cellular pathways of transport. Chapter 2 considers how the mobility of solutes can be measured and the range of chemical species which are moved in xylem and phloem. The next chapter discusses the concepts of velocity and rate. The rest of the book is devoted to the characteristics of phloem transport and the ultrastructure of sieve elements, including such topics as the control of movement, solute-loading and -unloading mechanisms, the dependence of transport upon metabolic energy, bidirectional movement and water movement in phloem. Finally an account is given of the movement of endogenous growth regulators and a brief assessment of 'hormone-directed' transport. Botanists will find the book very interesting and informative.


Courses

The Department of Soil Science offers over 40 courses at levels ranging from introductory for non-majors, to advanced courses for majors in soils and allied disciplines. Departmental course offerings are periodically revised and updated, and new courses are developed to serve today’s students.

The Department of Soil Science is housed in the Soils Bldg., King Hall, and the Hiram Smith Annex. It is part of the College of Agricultural and Life Sciences (CALS).

The department’s graduate seminar series each semester focuses on topical issues and provides an exciting forum for faculty and graduate students to exchange ideas and information on a continuing basis.

All faculty members with research appointments advise graduate students enrolled in MS and PhD programs.

101 Forum on the Environment (2 cr. spring)/Thea Whitman ([email protected]). Course description: Lectures and discussions about environmental issues. Historical and contemporary environmental impacts of humans on the biosphere. Global futures: population, technology, societal values, resources and prospects for sustainable management. Crosslisted with: Environmental Studies. Prerequisites: none open to freshmen

131 Earth’s Soil: Natural Science & Human Use (1 cr. fall)/Alfred Hartemink ([email protected]). Course description: An overview of the soils of the world and the grand environmental challenges that face humanity. Soils of the USA and Wisconsin included. Prerequisites: none

132 Earth’s Water: Natural Science & Human Use (3 cr. spring)/Mattie Urrutia ([email protected]). Course description: Water is central to the functioning of planet Earth. As humans increase their impact on Earth’s systems and cohabitants, our understandin.g of the multiple roles of water becomes critical to finding sustainable strategies for human and exosystem health. This course explores the science of Earth’s hydrosphere, with constant attention to human uses and impacts. Crosslisted with: Atmospheric and Oceanic Systems. Prerequisites: none

230 Soil: Ecosystem & Resource (3 cr. spring)/Nick Balster ([email protected]). Course description: Soils are fundamental to ecosystem science. A systems approach is used to investigate how soils look and function. Topics investigated include soil structure, biology, water, fertility, and taxonomy as well as the human impact on the soil environment. Crosslisted with: Environmental Studies and Geography. Prerequisites: Students who have credit for SOIL SCI 301 may not enroll in this course.

250 Introduction to Environmental Science (3 cr. fall 2019)/Nick Balster ([email protected]). Course description: Designed to introduce the interdisciplinary field of Environmental Science by providing a broad overview of the basic concepts used to make sense of the environment. Explore how natural systems work, the services they provide, important environmental challenges facing these systems, and how people are working to address them. Includes professionals in the field as guest speakers to discuss a future in Environmental Sciences. Pre-requisites: None

299 Independent Study (1-3 cr. all terms) Students are responsible for arranging the work/credits with a supervising instructor. Course description: Provides academic credit for research work under direct guidance of a faculty or instructional academic staff member. Students are responsible for arranging the work and credits with the supervising instructor. Prerequisites: Consent of instructor

301 General Soil Science (4 cr. fall)/Doug Soldat & Phil Barak (lecture), Mattie Urrutia (lab) ([email protected] [email protected] [email protected]). Course description: Physical chemical and biological properties of soils as they affect soil-plant-water relations, soil classification and suitability for agricultural and other uses. Prerequisites: (CHEM 103, 109, or 115) and (MATH 112, 114, or 171)

321 Soil & Environmental Chemistry (3 cr. fall)/Will Bleam ([email protected]). Course description: Undergraduate students majoring in soil science, environmental science, geology and chemistry are the target audiences for this course. The emphasis is chemistry fundamentals in the environmental context. Some topics are not covered in college-level general chemistry: clay mineralogy, ion exchange, and adsorption reactions. This course applies biological chemistry to both natural organic matter and reductionoxidation chemistry. Chemical hydrology and risk assessment are topics professional environmental chemists will likely encounter. Prerequisites: CHEM 104, 109 or 116

322 Physical Principles of Soil & Water Manage-ment (3 cr. spring)/Jingyi Huang ([email protected]). Course description: Soil physical properties and interactions as related to soil and water resource management and conservation. Water runoff (leading to soil erosion and surface water contamination) tillage and nutrient management soil thermal and moisture regimes solute movement soil compaction, air and aeration. Prerequisites: (PHYSICS 103, 201, 207 or 247) and SOIL SCI 301

323 Soil Biology (3 cr. fall)/Matt Ruark, Zac Freedman & Ann Macguidwin ([email protected] [email protected]). Course description: Nature, activities and role of organisms inhabiting soil. Effects of soil biota on ecosystem function, response to cultural practices, and impacts on environmental quality, including bioremediation of contaminated soils. Crosslisted with: Plant Pathology. Prerequisites: (BIO/BOT/ZOO 152, or BIO/ZOO 101 and BIO/ZOO 102 and BIO/BOT 130, or BIOCORE 381, 382, 383, and 384) and (CHEM 104, 109, or 116)

324 Soils & Environmental Quality (3 cr. summer-online only)/Mattie Urrutia ([email protected]). Course description: Interaction of soils with environmental contaminants and the role of soils in pollution control. Crosslisted with: Environmental Studies. Prerequisites: CHEM 104, 109, or 116

325 Soils & Landscapes (3 cr. fall)/Alfred Hartemink ([email protected]). Course description: Learn how to read the landscape and understand the relationships between soils, land use and landform. Discuss soil-forming factors, soil processes, soil classification, the 12 soil orders, soil survey and mapping. We will make several field trips and attendance is essential and required. Prerequisites: none

326 Plant Nutrition Management (3 cr. spring)/ Phil Barak ([email protected]) lecture Mattie Urrutia ([email protected]) lab. Course description: Functions, requirements and uptake of essential plant nutrients chemical and microbial processes affecting nutrient availability diagnosis of plant and soil nutrient status fertilizers and efficient fertilizer use in different tillage systems. Crosslisted with: Agronomy and Horticulture. Prerequisites: (CHEM 103, 109, or 115 and ENVIR ST/GEOG/SOIL SCI 230) or SOIL SCI 301

332 Turfgrass Nutrient & Water Management (3 cr. even numbered fall)/Doug Soldat ([email protected]). Course description: Nutrient requirements of turfgrasses nature of turfgrass response to fertilization soil and tissue testing methodology and interpretation irrigation scheduling irrigation water quality use of irrigation and fertilizer to minimize environmental impact writing effective nutrient management plans. Crosslisted with: Horticulture. Prerequisites: none

375 Topic Courses. Course description: Special topics on contemporary issues relevant to soil science. Prerequisites: Consent of instructor

430 Environmental Soil Contamination (3 cr. spring 2020)/Ed Boswell ([email protected]). Course description: Examine the sources and properties of anthropogenic soil pollution including emerging contaminants such as PFAS, nanomaterials, microplastics. Apply the principles of soil science to understand the transport, mobilization, and partitioning of contaminants in soil and, in turn, how these contaminants affect ecosystem and human health. Through industry guest lecturers and case studies discuss methods to solve issues of soil contamination. Pre-requisites: Chem 104 or 109 or 116 or Graduate/professional student standing

499 Capstone (3 cr. fall)/Nick Balster or Steve Ventura ([email protected]/[email protected]). Course description: A capstone applying independent and team problem solving, critical thinking and oral and written communication skills to issues in soil and environmental sciences. Crosslisted with: Environmental Studies 600. Prerequisites: Senior standing only declared Soil Science or Environmental Sciences programs

523 Soil Microbiology & Biogeochemistry (3 cr. spring)/Thea Whitman ([email protected]). Course description: Transformations of nutrients and contaminants in soils and groundwater by microorganisms: emphasis on enzymatic mechanisms and metabolic pathways. Approaches for analyzing microbial populations and activities including molecular techniques. Applications of microbial activities for bioremediation of contaminated soils and groundwater. Students should have completed one course in either Soil Science or Microbiology to feel comfortable with the course content. Crosslisted with: Microbiology. Prerequisites: (CHEM 104, 109, or 116) and (BIO/ZOO 102, BIO/BOT 130, or BIO/BOT/ZOO 151) Senior standing

524 Urban Soil & the Environment (3 cr. odd numbered fall – online)/Nick Balster ([email protected]). Course description: Many environmental issues related to urbanization are derived from the manipulation of soil. By coupling contemporary literature in urban soils with soil science, students will be able to evaluate environmental issues within the urban environment and provide new ways of remediating their impact. Crosslisted with: Forest & Wildlife Ecology and Horticulture. Prerequisites: (PHYSICS 103, 201, 207, or 247) and (ENV ST/GEOG/SOIL SCI 230 or SOIL SCI 301 or concurrent)

532 Environmental Biophysics (3 cr. fall)/Chris Kucharik ( kucharik @wisc.edu). Course description: Plant-environment interactions with particular reference to energy exchanges and water relations. Models are used to provide a quantitative synthesis of information from plant physiology, soil physics, and micrometeorology with some consideration of plant-pest interactions. Students should have completed at least one course in Botany, Agronomy, or Plant Sciences to feel comfortable with the course content. Crosslisted with: AGRON, ATMO. Prerequisites: (BOT/BIOL 130) and (MATH 211, 217, 221 or 275) and (PHYSICS 103, 201, 207, or 247) Graduate/professional standing

575 Assessment of Environmental Impact (3 cr. even numbered spring)/Steve Ventura ([email protected]). Course description: Overview of methods for collecting and analyzing information about environmental impacts on agricultural and natural resources, including monitoring the physical environment and relating impacts to people and society. Crosslisted with: Environmental Studies. Prerequisites: Junior standing

621 Advanced Soil & Environmental Chemistry (3 cr. spring)/Will Bleam ([email protected]). Course description: Solubility relationships, complex ions, ion exchange and oxidation-reduction reactions in soils. Prerequisites: CHEM 104, 109, or 116

622 Soil Physics (3 cr. fall)/Jingyi Huang ([email protected]). Course description: Physical properties of soils. Water retention and transmission in soils. Transport of heat, gas, and solutes. Physical environment of soil organisms and soil-plant-water relations. Prerequisites: (MATH 104, 109, or 116) and (PHYSICS 104, 202 208, or 248) and SOIL SCI 301

626 Mineral Nutrition of Plants (3 cr. odd numbered fall)/Phil Barak & Edgar Spalding ([email protected]). Course description: Essential and beneficial elements, solutions and soil as nutrient sources, rhizosphere chemistry, nutritional physiology, ion uptake and translocation, functions of elements, nutrient interactions, genetics of plant nutrition. Crosslisted with: Botany and Horticulture. Prerequisites: Graduate student or BOT 500

631 Toxicants in the Environment: Sources, Distribution & Fate (3 cr. spring)/Joel Pedersen ([email protected]). Course description: Nature, sources, distribution, and fate of contaminants in air, water, soil, and food and potential for harmful exposure. Crosslisted with: M& Environmental Toxicology and Civil & Environmental Engineering. Prerequisites: (CHEM 104, 109, or 116) and (MATH 211, 217, 221 or 275) and (PHYSICS 104, 202, 208, or 248)

695 Application of GIS in Natural Resources (3 cr. spring)/Steve Ventura (odd yrs [email protected]) Janet Silbernagel (even yrs [email protected]). Course description: Course has four components: 1) Detailed review of GIS concepts 2) Case studies 3) GIS implementation methods 4) Laboratory to provide “hands-on” GIS experience. Crosslisted with: Landscape Architecture and Environmental Studies. Prerequisites: Geography 377

699 Special Problems (Individual study for majors arrange w/faculty member). Course description: Individual study for majors completing theses for Soil Science degrees as arranged with a faculty member. Prerequisite: Requires consent of supervising instructor

728 Graduate Seminar (1 cr. fall & spring)/Will Bleam ([email protected]). Course description: Topical oral presentations by guest speakers and graduate students on contemporary concerns and issues involving land and soils.Prerequisites: Graduate standing

799 Practicum: Soil Science Teaching (1-3 cr. fall & spring)/Instructional orientation to teaching at higher level. Course description: Instructional orientation to teaching at the higher education level in the agricultural and life sciences, direct teaching experience under faculty supervision, experience in testing and evaluation of students, and the analysis of teaching performance. Prerequisites: Graduate standing

875 Special Topics (Special topics in contemporary issues). Course description: Special topics on contemporary issues relevant to soil science. Prerequisite: consent of instructor

990 Research (credits vary fall, spring, summer)/ Independent research & writing to complete dissertation requirements. Course description: Independent research and writing to complete dissertation requirements. Prerequisites: Graduate standing


Watch the video: Part 2Plus 1BotanyBiology. Plant water relations. Water potentialOsmosisTransport in plants (September 2022).


Comments:

  1. Samugrel

    What comes out of this?

  2. Padraig

    I deleted the sentence

  3. Chinua

    I regret, that I can not participate in discussion now. It is not enough information. But with pleasure I will watch this theme.

  4. Adrik

    And with this I have come across. We can communicate on this topic.

  5. Taj

    Do something serious

  6. Kuhlbert

    Understand me?



Write a message