Factors That Affect The Number Of Stoma On A Leaf.

... Factors That Affect The Number Of Stoma On A Leaf. Stomata are specialised pors on the epidermis of the leaves and stems of plants, which have the capability of opening and closing. The opening and closing of the stomata are contolled by a pair of modified epidermal cells called guard cells. The principle fuctions of stomata are gas exchange for photosynthesis and the evaporation of water as part of the transpiration stream. The stomata open and close due to changes in turgor pressure within the guard cells. In the centre of each guard cell is a sap filled vacuole that can swell with increasing turgor pressure. Guard cells increase their turgor pressure by accumulating K+ ions thus lowering their water potential allowing an osmotic flow of water into the cell. Because the inner cell was is thicker and less elastic than the outerwall the cell expnads unevenly. They bend and draw away

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