1. 1 Sentinel Molecular Diagnostics for Crop Agroterrorism Dr. Joe Eugene Lepo Center for Environmental Diagnostics and Bioremediation University of West Florida, Pensacola Tuesday, February 13th, at 4:30 – 5:30 p.m. Ruhl Student Center, Community Room STSS07 Schedule & Abstract Site (click here)

2. 2 Water Relations Chapter 5

3. 3 Water Availability The tendency of water to move down concentration gradients, and the magnitude of those gradients, determine whether an organism tends to lose or gain water from its environment. Must consider an organisms microclimate in order to understand its water relations.

4. 4 Water Content of Air Evaporation accounts for much of water lost by terrestrial organisms. As water vapor in the air increases, the water concentration gradient from organisms to air is reduced, thus evaporative loss is decreased. Evaporative coolers work best in dry climates.

5. 5 Evaporative Water Loss

6. 6 Water Movement in Aquatic Environments Water moves down concentration gradient. Water is more concentrated in freshwater environments than in the oceans. Aquatic organisms can be viewed as an aqueous solution bounded by a selectively permeable membrane floating in an another aqueous solution.

7. 7 Water Movement in Aquatic Environments If two environments differ in water or salt concentrations, substances will tend to move down their concentration gradients. Diffusion Osmosis: Water diffusion through a semipermeable membrane.

8. 8 Water Movement in Aquatic Environment Isomotic: Body fluids and external fluid are at the same concentration. Hypoosmotic: Body fluids are at a higher concentration than the external environment. Water diffuses into body. Hyperosmotic: Body fluids are at a lower concentration than the external environment. Water diffuses out of body. http://www.unk.edu/acad/biology/hoback/marineinsects/salthyp.htm

9. 9 Water Movement Between Soils and Plants plant = solute + matric + pressure Matric Forces: Waters tendency to adhere to container walls. pressure is the reduction in water potential due to negative pressure created by water evaporating from leaves. As long as plant > soil, water flows from the soil to the plant.

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11. 11 Water Regulation on Land Terrestrial organisms face (2) major challenges: Evaporative loss to environment. Reduced access to replacement water.

12. 12 Water Regulation on Land - Animals W ia = W d + W f + W a - W e - W s W ia = Animals internal water W d = Drinking W f = Food W a = Absorbed by air W e = Evaporation W s = Secretion / Excretion

13. 13 Water Regulation on Land - Animals

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15. 15 Water Regulation on Land - Plants W ip = W r + W a - W t - W s W ip = Plants internal water W r =Roots W a = Air W t = Transpiration W s = Secretions

16. 16 Water Regulation on Land - Plants

17. 17 Water Acquisition by Animals Most terrestrial animals satisfy their water needs via eating and drinking. Can also be gained via metabolism through oxidation of glucose: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Metabolic water refers to the water released during cellular respiration.

18. 18 Dipodomys merriami. Photographer: Dr. Lloyd Glenn Ingles. Copyright © 1999 California Academy of Sciences.

19. 19 Water Conservation by Plants and Animals Many terrestrial organisms equipped with waterproof outer covering. Concentrated urine / feces. Condensing water vapor in breath. Behavioral modifications to avoid stress times. Drop leaves in response to drought. Thick leaves Few stomata Periodic dormancy

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22. 22 Dissimilar Organisms with Similar Approaches to Desert Life Camels Can withstand water loss up to 20%. Face into sun to reduce exposure. Thick hair: Increased body temperature lowers heat gradient. Saguaro Cactus Trunk / arms act as water storage organs. Dense network of shallow roots. Reduces evaporative loss.

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24. 24 Two Arthropods with Opposite Approaches to Desert Life Scorpions Slow down, conserve, and stay out of sun. Long-lived Low metabolic rates Cicadas (Diceroprocta apache) Active on hottest days. Perch on branch tips (cooler microclimates). Reduce abdomen temp by feeding on xylem fluid of pinyon pine trees.

25. 25 Water and Salt Balance in Aquatic Environments Marine Fish and Invertebrates Isomotic organisms do not have to expend energy overcoming osmotic gradient. Sharks, skates, rays - Elevate blood solute concentrations hyperosmotic to seawater. Slowly gain water osmotically. Marine bony fish are strongly hypoosmotic, thus need to drink seawater for salt influx.

26. 26 Osmoregulation by Marine Organisms

27. 27 Water and Salt Balance in Aquatic Environments Freshwater Fish and Invertebrates Hyperosmotic organisms that excrete excess internal water via large amounts of dilute urine. Replace salts by absorbing sodium and chloride at base of gill filaments and by ingesting food.

28. 28 Osmoregulation by Freshwater Organisms