In guard cells when sugar is converted into starch, the stomatal pore
1. Opens partially
3. Closes completely
2. Opens completely
4. Remains unchanged
(2) Starch levels increase during stomatal closure, and decline during stomatal opening. This is consistent with a role for starch as a source of carbon skeletons for PEP synthesis and hence malate synthesis. During stomatal opening, when malate is accumulated, starch levels decline as the carbon is used in the synthesis of PEP
Diffusion is very imporatnt to plants since:
1. The cells have a permeable cell wall
2. It is the only means for gaseous movement within the plant body.
3. Plants cannot transport material by active transport.
4. They are unable to move towards the source of the nutrients.
Read page 176, XI NCERT
Which of the following is not a characteristic of facilitated transport in plants?
1. Requirement of special membrane proteins
2. Being non-selective
3. Transport saturates
4. It is a downhill transport
Read page 178, Table 11.1, XI NCERT
If a pressure greater than atmospheric pressure is applied to a solution, its water potential:
3. Remains same
4. Becomes zero
Read page 179, XI NCERT
Water movement in plants is:
1. Down a potential gradient in apoplast and up the potential gradient in symplast
2. Down a potential gradient in symplast and up the potential gradient in apoplast
3. Up the potential gradient in both apoplast and symplast
4. Down the potential gradient in both apoplast and symplast
Read page 185, XI NCERT
What per cent of water reaching them is used by leaves in photosynthesis?
1. Less than 1%
2. About 5 %
3. About 5 % in warm conditions and about 10 % in cold conditions
4. About 50 %
(1) Read page 187, XI NCERT
Attraction of water molecules to polar surfaces [such as the surface of tracheary elements] is called as:
Read page 188, XI NCERT
What are the control points where a plant adjusts the quantity and types of solutes that reach the xylem?
1. Suberin deposited casparian strips
2. Transport proteins of endodermal cell
3. Sclerenchyma around the pericycle
4. The root hairs themselves
(2) Read page 189, XI NCERT
Consider the following two statements:
I. The direction of movement in the phloem is bi-directional.
II. The source-sink relationship in plants is variable.
1. Both I and II are correct and II explains I
2. Both I and II are correct but II does not explain I
3. I is correct but II is incorrect
4. Both I and II are incorrect
Read page 190, XI NCERT
During translocation of sugars in plants from source to sink:
1. The loading of sugar at source is by active transport and unloading at the sink by passive transport.
2. The loading of sugar at source is by passive transport and unloading at the sink by active transport.
3. Both loading at the source and unloading at the sink are by active transport.
4. Both loading at the source and unloading at the sink are by passive transport.
Read page 191, XI NCERT