In this process, water evaporates from the surface of a
leaf through microscopic pores known as STOMATA. The loss of water
creates a suction force that pulls up more water from the roots. Transpiration
helps a plant to collect vital minerals from the soil. The amount of water lost
from the leaves depends on how much water is in the soil, as well as other
environmental conditions, such as temperature, humidity, and wind.
Water in plants is both pushed and pulled upwards inside transport
pipes called xylem. This continuous flow of water is known as the transpiration
stream and keeps the stem firm so that it can support the weight of the plant.
The transpiration stream also transports water to the plant’s leaves for
photosynthesis and carries minerals around the plant.
Plants need a continuous supply of water to stand upright. Each
plant cell holds water in swollen bags called vacuoles. This water pushes
against the cell walls and keeps the cell firm. This pressure and firmness of
plant cells is called turgor.
The surface of a leaf has many tiny pores, called
stomata. The stomata allow carbon dioxide into the leaf so that photosynthesis
can occur. They also allow water to leave the leaf by transpiration. Plants
that grow in full sunlight usually have most of their stomata on the shaded
undersides of their leaves. This helps the plant to conserve water.
Each individual stoma (stomata is the
plural) in the leaf’s surface is surrounded by two guard cells, which
look a bit like lips. During the day, these guard cells swell with water and
become bloated, opening the stoma. At night, the guard cells release their
water and the stomata close.
