posted by Pamela on .
The amount of water needed daily by plants for photosynthesis, cell growth, and cell maintenance is very small, and yet plants require large volumes of water in order to live. It is estimated that over 90 percent of the water absorbed by plants is lost into the air. Most of the water loss is due to evaporation from the plant through the small openings in leaves called stomata. This loss of water vapor from plants is referred to as transpiration.
The data represent the average transpiration value for twenty plants under each of the six experimental conditions. The room conditions were a temperature of 22°C, fluorescent lighting, and low humidity.
3) Which of the following statements best explains the results associated with condition 5?
a) when a fan was added to heat and additional light, the rate of transpiration was slowed to the rate associated with room conditions, because the fan cooled the plants.
b) Additional heat and light and air movements caused the plants to loose so much water, that after five minutes, they wilted, thereby closing their stomata and preventing further water loss.
c) Additional heat resulted in such severe water loss that it could not be counteracted by air movement caused by the fan and the plants died.
d) After five minutes, the rate of transpiration gradually increased, because moisture was being brought up the stem more rapidly.
4) Which of the following hypotheses about the effects of high humidity is supported by the graph?
a) Plants will grow faster
b) Plant tissues will contain a smaller volume of water
c) Plants will close their stomata
d) Evaporation will proceed more slowly
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3. B) Additional heat and light and air movement caused the plants to lose so much water that after five minutes they wilted, thereby closing their stomata and preventing further water loss.
4. A) Plants will grow faster.
Which of the following hypotheses about the effects of high humidity is supported by the graph?
A) Plants will grow faster.
B) Plant tissues will contain a smaller volume of water.
C) Plants will close their stomata.
D) Evaporation will proceed more slowly.
3. B (correct)
4. D (correct)