Transpiration is the process by which plants absorb water from the soil, circulate it to all the branches and leaves to eventually release water vapor in the atmosphere through the pores of the leaves.
Like animals, plants need water to survive. The root of a plant absorbs water from the soil. The absorbed water travels up the stem and the veins carry the water to the leaves. Upon the necessary absorption of water by the cells of the plant, at the root, stem, branches and leaves, the excess water is released in the form of water vapor through the stoma of the leaves. Water is pivotal to the survival of plants.
Plants can absorb groundwater through the roots, they can absorb surface water and it can also use rainwater. The leaves and the stem or the branches would absorb water but not to an extent that the roots are capable of. The roots are the most capable absorber of water, which is why one has to water the roots or the ground and not just the leaves of the plants. Even if you spray water on the leaves and stems, the larger quantum of the water sprayed would accumulate at the ground, moistening the soil wherefrom the root would extract the water, rendering the soil dry.
Significance of Transpiration
Transpiration is crucial for the survival of plants. But it is also crucial for the animal kingdom and also the ecology. Transpiration is largely responsible for the water vapor available in the atmosphere and that is also what contributes substantially to the different forms of precipitation.
The sun plays a significant role in evaporation and that leads to rainfall. However, not every region in the world has available surface water, be it rivers, lakes or seas to facilitate evaporation of enough moisture to bring in sufficient rains. The water vapor released by the leaves of the plants lead to a greater accumulation. There is a reason why rainforests or heavily forested areas get more rainfall.
Transpiration can make groundwater available in the atmosphere since the roots extract the moisture and the water vapor is eventually released by the leaves. This groundwater is not exposed to the sun and thus cannot contribute to the evaporation necessary for adequate condensation and subsequent precipitation.
Transpiration is a significant process to maintain the ecological balance. The cutting of trees and thus the decline of water vapor released at the end of transpiration is directly impacting the ecology and that is facilitating global warming.