Support and transport in plants

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Structural modifications of leaves to reduce water loss (Internal factors limiting transpiration)

Sunken stomata: In some plants stomata may be sunken or small.

Thickened cuticle: A thick cuticle on the surface of leaves reduces the rate of transpiration.

Hair on leaves: the sheen r shine of the hairs of some leaves reflect sunlight and reduces transpiration. Hairs also trap water vapour, restricting water loss.

Shape, size and arrangement of leaves: The shape and size of leaves determine the total surface area exposed to the environment, and hence influence the rate of transpiration. The leaves of some plants are arranged in such manner that they shade each other or overlap each other. In this water loss is restricted

Slide 34

Environmental factors affecting the rate of transpiration

Humidity: High humidity decreases transpiration rate

Wind: Increases evaporation and thus transpiration

increases. Wind removes the water vapour around leaf thus increasing water vapour pressure gradient.

Temperature: Increases evaporation and thus transpiration

Light: generally causes an increase in the rate of transpiration

Slide 35

Wilting: Loss of turgidity of the cells results in leaves and

Sometimes the stems, becoming limp, causing them to droop.

Then the plant is called wilting.

Guttation: Loss of liquid water through tiny pores, called

hydathodes on margin of leaf.

Wilting Plant

Guttation

Slide 36

Economic uses of plants related to their anatomy:

Paper

Clothing

Timber for furniture-making and building construction

Basket-making

Thatching, matting and broom-making