Question

What is transpiration? Where does it occur?

Answer 1

Hint Plant does not consist of a circulatory system, the movement of various substances in a plant takes place by its cells. The main substance transported in a plant is water, minerals, organic nutrients, and hormones. The plant absorbs a large amount of water but it uses less than 1% of water for photosynthesis and growth.

Complete Answer:
Transpiration is the loss of water in form of vapour from various parts of the plant cell-like stomata, lenticels, and epidermal cells. Transpiration mainly takes place in the aerial part of the plant, stomata of leaves evaporate high amounts of water in form of vapour which helps to keep the plant cool. Cellulose microfibrils open the stomata when guard cells lose turgor, due to loss of water the inner wall regains their original shape and becomes flaccid.

Additional information:
The rate of transpiration is affected by several internal and external factors. Internal factors include leaf area, leaf structure, succulence, and root- shoot ratio. In the case of the leaf area plants with larger leaves evaporate more water than smaller leaves. Plant in the arid region bears small leaves while the plant in the desert has leaves modified into the spine to minimize transpiration. On the basis of structure, the plant with leaves covered with a wax coating, epidermal hair, and thick cuticle reduce transpiration. The succulent photosynthetic stem also reduces transpiration by the presence of mucilage and latex in their tissue. The rate of transpiration increases with an increase in the root-shoot ratio.
External factors affect that transpiration is relative humidity, light, temperature, wind, soil water, and carbon dioxide concentration.

Note: In both transpiration and guttation loss of water take place but transpired water is pure water and guttation water is a dilute solution of organic and inorganic substances. Transpiration mainly occurs through stomata whereas guttation occurs through hydathodes.