The greatest contribution of root pressure in water transport in plants most likely is that it:
1. | pushes water to the top at night |
2. | pushes water to the top of the plant when the rate of transpiration is low |
3. | re-establishes the continuous chain of water molecules in the xylem |
4. | pushes water into the endodermal cells changing the transport from apoplast to symplast |
In a guard cell:
I. The outer walls are thick and elastic
II. Cellulose microfibrils are oriented longitudinally
1. Only I is correct
2. Only II is correct
3. Both I and II are correct
4. Both I and II are incorrect
Cohesion, adhesion and surface tension provide water with a high tensile strength that means that it:
1. is capable of rising in a thin tube
2. has a low specific heat
3. resists a pulling force
4. is a universal polar solvent
The evolution of C4 photosynthetic system is probably one of the strategies for:
1. | maximizing the availability of oxygen in spite of continuing high amount of water loss |
2. | maximizing availability of water in spite of continuing high amount of carbon dioxide loss |
3. | reducing the amount of water loss but leads to decreased availability of carbon dioxide |
4. | maximizing the availability of carbon dioxide while minimizing water loss |
The control points where a plant adjusts the quality and types of solutes that reach the xylem are:
1. Transport proteins of endodermal cells | 2. Root hair |
3. Parenchyma cells of the root cortex | 4. Casparian strips |
Unloading of mineral ions occurs at the fine vein endings through:
1. diffusion and, are passively taken up by the sink cells
2. active transport and, are passively taken up by the sink cells
3. diffusion and, are actively taken up by the sink cells
4. active transport and, are actively taken up by the sink cells
An analysis of xylem exudates will show that most of the nitrogen is carried as:
1. Inorganic ions
2. Ammonia dissolved in water
3. Dinitrogen
4. Organic compounds such as amino acids
Unlike xylem, the movement of sap in phloem is:
1. essentially unidirectional
2. from a sink to a source
3. independent of movement of water
4. in any direction from source to a sink
During mass flow in phloem, active transport is required:
1. For uploading sap
2. For unloading sap
3. Both for uploading and unloading the sap
4. Active transport is not required
In section 11.1.2, NCERT states that a concentration gradient needs to be present in spite of the fact that facilitated diffusion is facilitated by a carrier. Why is it so?
1. These protein carriers have ATPase activity.
2. These protein carriers can not move in the membrane.
3. These protein carriers can not establish concentration gradients.
4. These protein carriers can provide only symport with the use of external energy.