Q. No.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.
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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Reducing transpiration yet allowing the normal growth of a plant would be possible by:
1. increasing the potassium channels in the guard cells
2. increasing the level of carbon dioxide around the plant
3. growing the plant in soils with low water content
4. decreasing the relative humidity around the plant
The presence of chloroplasts in guard cells is important because:
1. chloroplasts have a light sensitive receptor to direct stomatal opening.
2. photosynthesis provides the energy necessary for synthesis of cellulose microfibrils.
3. oxygenic photosynthesis produces oxygen necessary to power active transport.
4. ATP is required to power proton pumps in the guard cell membranes.
The Casparian strip ensures that only selective substances may pass through the:
1. root hairs.
2. root cortex.
3. ground tissue.
4. endodermis.
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Opening of guard cells is facilitated by:
I. accumulation of potassium accumulates within the guard cell.
II. movement of chloride into the guard cells.
III. membrane potential created by proton pumps.
1. I and II only
2. I and III only
3. II and III only
4. I, II and III
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