Transcript INTRODUCTION

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)
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Water Relations
Chapter 5
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Water Availability
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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 organism’s microclimate
in order to understand its water relations.
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Water Content of Air
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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.
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Evaporative Water Loss
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Water Movement in Aquatic Environments
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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.
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Water Movement in Aquatic Environments
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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.
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Water Movement in Aquatic Environment
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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
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Water Movement Between Soils and Plants
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plant = solute + matric + pressure
Matric Forces: Water’s 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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Water Regulation on Land
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Terrestrial organisms face (2) major
challenges:
 Evaporative loss to environment.
 Reduced access to replacement water.
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Water Regulation on Land - Animals
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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 Regulation on Land - Animals
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Water Regulation on Land - Plants
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Wip= Wr + Wa - Wt - Ws
Wip= Plant’s internal water
Wr =Roots
Wa = Air
Wt = Transpiration
Ws = Secretions
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Water Regulation on Land - Plants
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Water Acquisition by Animals
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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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Dipodomys merriami. Photographer: Dr. Lloyd Glenn Ingles.
Copyright © 1999 California Academy of Sciences.
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Water Conservation by Plants and Animals
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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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Dissimilar Organisms with Similar
Approaches to Desert Life
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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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Two Arthropods with Opposite
Approaches to Desert Life
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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.
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Water and Salt Balance in Aquatic Environments
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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.
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Osmoregulation by Marine Organisms
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Water and Salt Balance in Aquatic Environments
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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.
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Osmoregulation by Freshwater Organisms
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