Large, empty colorless cells of the adaxial epidermis along the veins of grass leaves are:
1. Lenticels
2. Guard cells
3. Bundle sheath cells
4. Bulliform cells
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