Water Relations

Question 1

water vapor pressure

Answer 1

• low temp, low saturation, low pressure
• pressure increases with higher saturation at higher temperatures
• water usually moves from organisms to atmosphere (approximated by vapour pressure deficit)

Question 2

vapour pressure deficit

Answer 2

differential between actual vapour pressure and saturation water vapour pressure
- high vpd = low water content in sky and high evaporation from organism

Question 3

hypo osmotic

Answer 3

high water (low salt)

Question 4

hyper osmotic

Answer 4

low water (high salt)

Question 5

osmotic pressure

Answer 5

created by movement of water

- larger osmotic differences between organism and environment - high osmotic pressure

Question 6

isosmotic

Answer 6

same concentrations

Question 7

water potential

Answer 7

capacity of water to do work

• flows from high water potential to lower
• pure water has a water potential of 0 (solutes reduce potential)

Question 8

matric forces

Answer 8

tendency for water to cling to soil particles and plant cell walls which reduces water potential

Question 9

water regulation on land

Answer 9

terrestrial plants and animals regulate internal water by balancing water acquisition against loss

Question 10

how do marine creatures balance salt and water?

Answer 10

• may be isosmotic to environment
• may be hyper osmotic

osmoregulation: regulation of internal salt and water by decreasing osmotic gradient between themselves and environment

Question 11

SIA - water uptake in plants

Answer 11

analysis of relative proportions of stable isotopes

2H and 18O are unusual in water and heavier so less likely to evaporate; more likely to precipitate
- surface water and ground water differ and can tell a plant’s water source