Table 1: Assimilation, stomatal conductance and intrinsic water use efficiency of wheat and maize plants grown in a glas

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Table 1: Assimilation, stomatal conductance and intrinsic water
use efficiency of wheat and maize plants grown in a glasshouse.
Plant
Treatment
Assimilation
(CO2 uptake)
Stomatal conductance(water loss)
WUE
(μmol m-2 s-1)
(mol m-2 s-1)
(µmol mol-1)
Wheat
Control
20
0.2
Wheat
Drought
0.08
Maize
Control
32
0.16
Maize
Drought
0.12
In an experiment on the effect of drought on wheat (a C3 crop)
and maize (a C4 crop) plants grown in a glasshouse, the components
of water use efficiency (WUE) were measured (Table 1).
QUESTIONS:
1a. Consider a scenario where after three days of drought the
assimilation rate of the C3 plants had fallen by 50% and by 30% for
the C4 plants. Calculate the new assimilation rates.
2b.WUE has changed as a result of drought stress. State
whether the C3 or C4 plants have improved their WUE, and explain
why this result occurs.
2c. Stomata control water loss from the plant to
atmosphere. Describe how changes in water status and osmoregulation
are involved in stomatal opening and closing. Including the role of
the subsidiary cells in this process.