Problems
61
The presence of the salt would therefore reduce the rate of cooling by
about 40 percent.
References
Robinson, R. A. and R. H. Stokes. (1965) Electrolyte solutions.
Buttenvorths. London.
Tracy, C. R. (1976) A model of the dynamic exchanges of water and energy between a terrestrial amphibian and its environment. Ecological
Monographs 43:293-326.
Problems
4.1. What is the gravitational potential at the top of a 30 m tall tree if the
reference is the soil surface?
4.2. What is the matric potential ofa loam soil at 0.15 kgkg water content?
4.3. The brine in the Great Salt Lake is mostly sodium chloride, and
reaches concentrations around 6 mol/kg in some places. Find the
osmotic potential of the brine. The osmotic coefficient (4) of 6 molal
NaCl is 1.27.
4.4. Find the vapor pressure and vapor mole fraction at the evaporating
surface of the Great Salt Lake (see 4.3) when its surface temperature
is 18" C. Its elevation is 1280 m.
4.5. If the temperature of a leaf is 33" C, estimate the vapor pressure at
the evaporating surfaces inside the stomata of the leaf.
4.6. If the total water potential of a leaf is -700 Jikg and the osmotic
potential is - 1200 Jikg, what is the turgor pressure in the cells?
4.7. Estimate the humidity inside an animal burrow where plants are
observed to be growing.
4.8. In plants sucrose is actively pumped, using metabolic energy, into the
phloem near the source of carbon fixation by photosynthesis. If the
concentration of sucrose outside the phloem is 0.5 molikg, the concentration inside the phloem is 1 mol/kg, and the sieve tube elements
are perfectly semipermeable, how much pressure could be built up
inside the sieve tube elements (assume
= O)? If the sucrose
is unloaded at some downstream location by the same mechanism,
so that the sucrose gradient is just reversed from that at the loading
site, what pressure difference will be maintained between the loading
and unloading zones in the phloem? This pressure difference is the
driving force for flow in the phloem.
61
The presence of the salt would therefore reduce the rate of cooling by
about 40 percent.
References
Robinson, R. A. and R. H. Stokes. (1965) Electrolyte solutions.
Buttenvorths. London.
Tracy, C. R. (1976) A model of the dynamic exchanges of water and energy between a terrestrial amphibian and its environment. Ecological
Monographs 43:293-326.
Problems
4.1. What is the gravitational potential at the top of a 30 m tall tree if the
reference is the soil surface?
4.2. What is the matric potential ofa loam soil at 0.15 kgkg water content?
4.3. The brine in the Great Salt Lake is mostly sodium chloride, and
reaches concentrations around 6 mol/kg in some places. Find the
osmotic potential of the brine. The osmotic coefficient (4) of 6 molal
NaCl is 1.27.
4.4. Find the vapor pressure and vapor mole fraction at the evaporating
surface of the Great Salt Lake (see 4.3) when its surface temperature
is 18" C. Its elevation is 1280 m.
4.5. If the temperature of a leaf is 33" C, estimate the vapor pressure at
the evaporating surfaces inside the stomata of the leaf.
4.6. If the total water potential of a leaf is -700 Jikg and the osmotic
potential is - 1200 Jikg, what is the turgor pressure in the cells?
4.7. Estimate the humidity inside an animal burrow where plants are
observed to be growing.
4.8. In plants sucrose is actively pumped, using metabolic energy, into the
phloem near the source of carbon fixation by photosynthesis. If the
concentration of sucrose outside the phloem is 0.5 molikg, the concentration inside the phloem is 1 mol/kg, and the sieve tube elements
are perfectly semipermeable, how much pressure could be built up
inside the sieve tube elements (assume
= O)? If the sucrose
is unloaded at some downstream location by the same mechanism,
so that the sucrose gradient is just reversed from that at the loading
site, what pressure difference will be maintained between the loading
and unloading zones in the phloem? This pressure difference is the
driving force for flow in the phloem.