Why is transpiration called a necessary evil?

Transpiration is called a necessary evil because it causes loss of water from plants but also performs several essential functions required for plant survival. Although excessive transpiration may lead to water deficiency and wilting, the process cannot be completely avoided because it supports important physiological activities.

During transpiration, plants lose water vapour mainly through tiny openings on leaves called stomata. This water loss creates a transpiration pull, which helps transport water and dissolved minerals from roots to different parts of the plant. Transpiration also helps regulate plant temperature by cooling the leaves.

It is considered an “evil” because large amounts of absorbed water are lost into the atmosphere, but it is “necessary” because it supports mineral transport, water movement, and temperature regulation. Therefore, transpiration is an important process for maintaining healthy plant growth.