Water Relations
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Transcript of Water Relations
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Water Relations
Chapter 6
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Outline
(I) Water Movement in Terrestrial Environments(II) Water Movement in Aquatic Environments(III) Water Regulation on Land(IV) Water and Salt Balance in Aquatic Environments
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(I) Water Movement in Terrestrial Environments
• Relative Humidity:
Water Vapor DensitySaturation Water Vapor Density (x 100)
• Water vapor density is measured as the water vapor per unit volume of air.
• Saturation water vapor density is measured as the quantity of water vapor air can potentially hold. Changes with temperature.
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(I) Water Movement in Terrestrial Environments
• Total Atmospheric Pressure Pressure exerted by all gases in the air.
• Water Vapor Pressure Partial pressure due to water vapor.
• Saturation Water Vapor Pressure Pressure exerted by water vapor in air
saturated by water.• Vapor Pressure Deficit
Difference between WVP and SWVP at a particular temperature.
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Evaporative Water Loss
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(II) 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: Diffusion through a semipermeable membrane.
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(II) 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.
• Hyperosmotic: Body fluids are at a lower concentration than the external environment.
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(III) Water Regulation on Land
• Terrestrial organisms face (2) major challenges: Evaporative loss to environment. Reduced access to replacement water.
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Water Regulation on Land - Plants
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Water Regulation on Land - Plants
• Wip= Wr + Wa - Wt - Ws
• Wip= Plant’s internal water• Wr =Roots• Wa = Air• Wt = Transpiration• Ws = Secretions
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Water Acquisition by Plants
• Extent of plant root development often reflects differences in water availability.
Deeper roots often help plants in dry environments extract water from deep within the soil profile.
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• Allocation of carbon to root tissues
Peppermint
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Water Conservation by Plants
• Many terrestrial organisms equipped with waterproof outer covering.
• Behavioral modifications to avoid stress times.
• Drop leaves in response to drought.• Thick leaves• Few stomata• Periodic dormancy
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當葉水勢能超過臨界值,植物關閉氣孔以節約水,光合作用便下降 . (Oak 較耐乾旱 )
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Water Regulation on Land - Animals
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Water Regulation on Land - Animals
• Wia= Wd + Wf + Wa - We - Ws
• Wia= Animal’s internal water• Wd = Drinking• Wf = Food• Wa = Absorbed by air• We = Evaporation• Ws = Secretion / Excretion
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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: C6H12O6 + 6O2 6CO2 + 6H2O
Metabolic water refers to the water released during cellular respiration.
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Water regulation of terrestrial animals
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Dissimilar Organisms with Similar Approaches to Desert Life
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Two Arthropods with Opposite Approaches to Desert Life
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(IV) Water and Salt Balance in Aquatic Environments
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(IV) Water and Salt Balance in Aquatic Environments
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• The End
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