Abstract

For an understanding of water economy in the rice plant it is essential to study the mechanism by which water is transpired in the plant. Transpiration takes place through the cuticle as well as through the stomata. In general it is recognised that in mesophytes, stomatal transpiration is 80 to 97 percent whereas cuticular transpiration is only 2 to 3 per cent. The total stomatal apertures in spite of their large number, occupy only one to two per cent of the total leaf surface. The epidermis along with the stomata possesses the physical properties of a multi-perforate septum and the diffusion of gases through these minute apertures proceeds almost at the same rate as if the cutinised epidermis were actually removed and the cells of the mesophyll were in direct contact with the external atmosphere'. It may be seen therefore that the stomata do play a very great part in the water balance of plants. The present study is restricted to stomatal sizes and their frequency in leaves of rice varities.

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