8.1 Transpiration in Plants

Objective: State that transpiration is the loss of water vapour from the plant through the stomata.

Transpiration is a crucial process in plants, essential for the movement of water and minerals from the roots to the rest of the plant. It involves the loss of water vapour from the plant, primarily through tiny pores on the leaves called stomata.

What is Transpiration?

Transpiration is essentially the evaporation of water from the aerial parts of a plant, mainly the leaves. This process is driven by the difference in water potential between the inside of the leaf and the surrounding atmosphere.

The Role of Stomata

Stomata are small openings, usually found on the lower epidermis of leaves. They are surrounded by guard cells, which regulate their opening and closing. When the guard cells take up water, they become turgid, causing the stomata to open. This allows water vapour to escape from the leaf.

The Process of Transpiration

1. Water is absorbed by the roots through osmosis.
2. This water travels up the xylem vessels in the stem to the leaves.
3. Inside the leaf, water evaporates from the mesophyll cells into the air spaces within the leaf.
4. Water vapour then diffuses out of the leaf through the stomata into the atmosphere.

Key Points about Transpiration

• Transpiration is a continuous process that occurs throughout the day.
• The rate of transpiration is affected by various environmental factors.
• Transpiration helps to cool the plant by removing heat.
• It also plays a vital role in the transport of water and minerals.

In summary, transpiration is the loss of water vapour from the plant through the stomata, a vital process for plant survival and function.