Question

define the term opening stomata and closing stomata

Answer 1

Stomata are small pores present in the epidermal cells of leaves in plants. Stomata are open during the day and close during night.Stomata take in carbon dioxide required for the photosynthetic activity during the day. They give out excess water released in the process of respiration during night along with carbon dioxide. Opening and closing of stomata is controlled by concentration of solutes in the guard cell.

Mechanism of opening and closing of stomata
Opening of stomata: Solutes from neighbouring epidermal and mesophyll cells enter the guard cells lowering its osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water into guard cells from neighbouring cells. Guard cells become turgid due to water accumulation in them which results in the opening of the guard cells.
Closing of stomata: As the somata open the solute concentration is reduced. This makes the water from the guard cells to move away into neighbouring cells. Now, guard cells becom flaccid with no water. They collapse against each other and result in the closing of stomata.

Answer 2

each stomata is surrounded by a pair of guard cells the guard cell control the opening and closing of stomata pores when the water enters into the guard cell they become turgid and swell as a result they become curved and stomata open when the guard cell loss water they shrink and become straight as a result the stomatal pores close