False-colour scanning electron micrograph of an open stoma,or pore,on the surface of a leaf of the tobacco plant,Nicotiana tabacum. Stomata are breathing pores scattered over the surface of the leaves,and sometimes the stem,of plants. They regulate the exchange of gases between the leaf's interior and the atmosphere. The closing of stomata is a natural response to darkness or drought,and is a mean of conserving water. Each pore is controlled by two guard cells,one on each side. When the guard cells are full of water,the pore is open; when they dry out,the pore closes. Magnification: x640 at 6x4.5cm size. JBU colouring: green & yellow. Original is BW print b745/176 |