Stomatal Transpiration

iii. Stomatal transpiration: Stomatal transpiration is water loss occurring through the stomata — minute pores in the epidermis, each formed by a pair of guard cells together with their surrounding accessory cells, located mainly in the epidermis of young stems and leaves. Leaves generally carry more stomata on their lower surface than their upper surface, and depending on exactly how stomata are distributed across the two leaf surfaces, leaves are grouped into three types: epistomatic leaves, which carry stomata mainly on the upper epidermis (typical of hydrophytes such as the lotus, whose lower surface may be submerged or in contact with water); hypostomatic leaves, which carry stomata mainly on the lower epidermis (typical of xerophytes such as Nerium, where keeping stomata off the sun-exposed upper surface helps reduce water loss); and amphistomatic leaves, which carry stomata on both surfaces roughly equally (typical of mesophytes such as grasses). …