Dear student,
Bulliform cells are the epidermal cells present on the upper leaf surface. When enough water is available to the leaf then water is taken up by the bulliform cells which becomes turgid then the surface of leaf spreads and becomes straight. But due to insufficiency of water, the bulliform cells losses water and becomes flaccid and the leaf curls to minimise the surface of leaf to be exposed for minimum water loss.
Regards
Bulliform cells are the epidermal cells present on the upper leaf surface. When enough water is available to the leaf then water is taken up by the bulliform cells which becomes turgid then the surface of leaf spreads and becomes straight. But due to insufficiency of water, the bulliform cells losses water and becomes flaccid and the leaf curls to minimise the surface of leaf to be exposed for minimum water loss.
Regards