What are the adaptations of the plant leaves to transpiration

There are many modifications to leaves that reduce transpiration, or water loss through leaves, especially on plants in arid regions. These include waxy surfaces such as on Aloe or a thick covering of hairs (pubescence) like a fur coat, as on *Asclepias* (Milkweed) or *Verbascum* (Mullein). Another adaptation is a severe reduction in the number of stomata on the leaves, a stoma, being the open pores through which water, a by-product of photosynthesis escapes, another is the ability to close the stoma completely by means of two kidney-shaped cells on either side of each stoma on the surface of the leaves. When they expand, together the pore is totally closed, conserving water. Another example is found in Ocotilla in the North American Sonoran desert (*Fouquieria), *a heavily spined, many tall stemmed shrub bearing red flowers at the stem tips in the Spring seasons if it rains, at the same time the leaves appear. When the dry season starts the leaves with their water-losing stomata simply drop off, and photosynthesis is carried on in the green bark of the stems.

 

Less leaf surface area results in reduced water loss through the epidermis. Small leaves have fewer stomata than larger leaves, and that adaptation also reduces water loss. Some dry-land plants have stomata only on the bottom epidermis, which further reducing water loss, and some have several layers of epidermal cells

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