Regarding the guard cells:
1. walls away from the stomatal pores are thin and those towards the stomatal pores are thick
2. walls away from the stomatal pores are thick and those towards the stomatal pores are thin
3. chloroplasts are mostly absent
4. play no role in the regulation of opening and closing of stomata

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