Q. No.Which of the following does not enter the plant through roots?
1. carbon dioxide
2. nitrogen
3. potassium
4. water
1. carbon dioxide
2. nitrogen
3. potassium
4. water
Wilting of leaves causes decline in photosynthesis because:
1. chloroplasts in wilted leaves cannot photosynthesize.
2. accumulation in the leaves inhibits Calvin cycle enzymes.
3. of lack of water for photolysis.
4. closure of stomata prevents entry of entry into the leaf.
Substances travelling via the symplast move from cell-to-cell through:
1. membrane proteins.
2. phospholipid channels.
3. tonoplast.
4. plasmodesmata.
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What happens to the tensile strength of fluid column with a decrease in the diameter of a tracheid?
1. It increases.
2. It decreases.
3. It approaches zero.
4. It approaches infinity.
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The pace at which transpiration takes place is primarily due to:
1. proton pumps.
2. phloem diameter sphincters.
3. cell wall expansion
4. guard cell dilation.
The most important problem faced by most plants during flooding is:
1. inability to receive sunlight
2. leaching of nutrients
3. damage to the root system
4. oxygen deprivation
Normally, the fastest delivery of water and minerals to the leaves of a tree is most likely to happen on a:
1. cool, dry day
2. warm, dry day
3. warm, humid day
4. very hot, dry, windy day
A decrease in potassium in the guard cells and surrounding epidermal cells would not lead to:
1. a decrease in photosynthesis.
2. a reduced uptake of water by roots.
3. closure of stomata.
4. a decrease in leaf temperatures.
Phloem transport differs from xylem transport as:
| 1. | Xylem transport requires active pumping at stomata, transport in phloem is passive. |
| 2. | Phloem movement is solar powered, xylem movement occurs best in dark. |
| 3. | Phloem carries fluid from the soil to the leaves, while xylem is the reverse. |
| 4. | Phloem can reverse direction, depending on the activity of the "source" and "sink" of its materials but the flow in xylem is essentially unidirectional. |
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Advantages of transpiration to the plants include:
I. evaporative cooling.
II. mineral transport.
III. increased turgor.
1. I and II only
2. I and III only
3. II and III only
4. I, II and III
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