Water and its relationship with plants

1. Water and its relationship with plants

2. Review definitions • Diffusion • Osmosis • Plasmolysis • Imbibition

3. Some new definitions • Active transport: movement of a substance against a diffusion or electrical gradient through the expenditure of energy • Proton pump in plants • Transpiration: loss of water at the surfaces of the plant

4. The study of plant functions and processes • Began ~ 1860s. Julius von Sachs is the father of plant physiology

5. Some processes that were known • Spontaneous vs. non-spontaneous • Spontaneous: no energy (E) or work is put into the system – physical process • Non-spontaneous: E is put into the system – chemical

6. Spontaneous • Diffusion in plants: substances moving with in and between the cells (phloem) • Water movement • Gas exchange inside the plant • Water vapor from the plant to the atmosphere • O2 and CO2 • Transpiration: water movement from areas of larger HOH pressure (potential) to areas of lower water potential (yw) • Pure water has the highest yw

7. Spontaneous cont. • Osmosis • Solvent (HOH) solute (sugar & dye) • The solvent did the moving, it went from high yw to low yw

8. Estuaries • Richest biomass area in the world. Organisms can survive in pure to very salty water • Compartmentalize the salt • Can decrease hydrostatic pressure (lower yw) • Ethylene glycol is built up in the cells of some algae to counter balance the increase salt in HOH

9. Spontaneous cont. • Turger : plants will take in increased concentration of HOH so the membrane of the cell is pushed up against the cell wall.

10. Turger allows the plant to stand up straight • Decreased HOH yields decreased turger pressure and thus wilting of the plant (flaccid) • If the amount of HOH transpired is > the HOH taken by the roots wilting occurs • If this goes on too long one gets permanent wilt • Temperature wilt can be reversed • HOH sets up different turger in various plant parts so the HOH can move to wilted areas to -> recovery

11. Spontaneous cont. • Some more definitions • Dispersions: cause to break up ‘something dispersed in HOH’ (soap) • Solutions: HOH solvent with solutes are small dissolved both (+) cations and (-) anions • Suspensions: particles that are large and held dispersed with in the solution ie. mud in HOH (not permanent)

12. Suspensions cont: make the particle small enough and the HOH molecule moving randomly can then keep the particle dispersed • Brownian movement: random movement of particles in HOH • Colloids: liquid in a liquid, liquid in a gas, solid in a liquid, solid in a gas

13. Colloids • Aerosols: solid or liquid particles in a gas.
Examples: Smoke is a solid in a gas. Fog is a liquid in a gas. • Sols: solid particles in a liquid.
Example: Milk of Magnesia is a sol with solid magnesium hydroxide in water. • Emulsions: liquid particles in liquid.
Example: Mayonnaise is oil in water. • Gels: liquids in solid.
Examples: gelatin is protein in water. Quicksand is sand in water.

14. Non-spontaneous • Non—spontaneous (metabolism) • 1 respiration, 2 photosynthesis, 3 N2 fixation • E is expanded • Accumulation • The membrane keeps selected ions out • Against the concentration gradients – work • Active process

15. The membrane keeps selected ions out • Against the concentration gradients – work • Protein transports stuff

16. Roots • Root system is large and numerous • Function • Anchorage and support • Absorption • Conduction and translocation (long distance movement ) • Miners of the soil • Storage • Steel • Xylem one way movement from root to leaf • Phloem two way movement nutrients from leaves up and down the stem and root

17. Essential elements • Found in ALL living organisms. Some only in plants/animals • Essential elements necessary for plant life • Criterion for being essential • 1. needed for normal growth and development with out this element plant would grow abnormally and usually dies • 2. Non-replaceable – must have the exact element, not a close match

18. Essential elements cont. • 3. Universality (everyone needs it) • Example: grasses and horse tailsEquisetum arvense require Si for normal growth, no other ‘regular’ pant needs Si, so this is not universal

19. Essential elements • Macronutrients • C, H, O - are structural building blocks for carbohydrates and fats • N - protein, nucleotides, nucleosides, energy of cell nucleic acids • P – those with phosphate bonds – RNA, DNA, metabolize carbohydrates phosphoralases break the Pi bonds • S – found in two essential amino acids S=S tertiary structures of RNA and protein – involved in all aromas of plants and animals (essences)

20. Essential elements • K – metabolic regulator , co-enzymes (enzymes changes shapes 2o to a metal giving or accepting e- • Guard cell function open with increased [K] -> low yw in cell. HOH goes in and guard cell thickens and flexes (opens the stomate) HOH vopor goes out – transpiration • Ca – membrane function and integrity – intercellular cement Ca pectate • First deficiency seen is Ca deficiency the growing point dies and the whole plant dies

21. Essential elements • Mg – structure of chlorophyll • Light receptor and e- donor • Sugar metabolism • Micronutrients measured as ppm and found in very small quantities

22. Water and Its Movement Through the Plant • Water Movement to Tree Tops • 1. Early theories • a. Mechanical pumps • b. Capillarity • c. Root pressure

23. The Cohesion-Tension Theory • 1. Polar water molecules stick together by hydrogen bonds • • called "cohesion" • 2. Water also sticks to walls of xylem tracheids and vessels • • called "adhesion" • 3. Water evaporates from mesophyll cells creating a pull or tension on the water column

24. Regulation of Transpiration • A. Regulation by Stomata • B. Effect of Abscisic Acid on Stomates • 1. Causes membranes to leak • 2. Loss of potassium occurs • 3. Stomates close as a result • C. Other Ways Plants Regulate Water Loss • 1. Stomates open at night • • desert plants with CAM photosynthesis • 2. Stomates sunken below leaf surface • • pine trees, desert plants

25. Regulation of Transpiration • D. Guttation • 1. Defined • • loss of water in liquid form • 2. Guttation water lost through hydathodes in leaves

26. Transport of Food Substances (Organic Solutes) in Solution • A. Insects and Sugar Flow • • aphids used to study sugar flow in plants • B. Use of Radioactive Tracers

27. Transport of Food Substances (Organic Solutes) in Solution • C. The Pressure-Flow Hypothesis • 1. Food substances in solution flow in phloem tissue from a "source" (a place where food is produced or stored) • • water is taken up by osmosis creating turgor pressure • 2. Food substances actively removed from the phloem at a "sink" (a place where food is utilized) • 3. Food substances flow from the region of higher pressure at the "source" to the lower pressure of the "sink"

28. END