Guard cells help in:
1. protection against grazing
2. transpiration
3. guttation
4. fighting against infection
Grass leaves curl inwards during very dry weather. Select the most appropriate reason from the following :
1. Tyloses in vessels
2. Closure of stomata
3. Flaccidity of bulliform cells
4. Shrinkage of air spaces in spongy mesophyll
Phloem in gymnosperms lacks:
1. Both sieve tubes and companion cells
2. Albuminous cells and sieve cells
3. Sieve tubes only
4. Companion cells only
Anatomically, fairly old dicotyledonous root is distinguished from the dicotyledonous stem by:
1. absence of secondary xylem
2. absence of secondary phloem
3. presence of cortex
4. position of protoxylem
The chief water conducting elements of xylem in gymnosperms are:
1. vessels
2. fibres
3. transfusion tissue
4. tracheids
Closed vascular bundles lack:
1. Ground tissue
2. Conjuctive tissue
3. Cambium
4. Pith
Companion cells are closely associated with:
1. Sieve elements
2. Vessel elements
3. Trichomes
4. Guard cells
Lenticels are involved in:
1. Gaseous exchange
2. Food transfer
3. Photosynthesis
4. Transpiration
Vascular bundles in monocotyledons are considered closed because:
1. | a bundle sheath surrounds each bundle |
2. | cambium is absent |
3. | there are no vessels with perforations |
4. | xylem is surrounded all around by phloem |