Describe
transpiration pull model of water transport in plants. What are the
factors influencing transpiration? How is it useful to plants?
Describe transpiration pull model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?
In tall
trees, water rises with the help of the transpirational pull
generated by transpiration or loss of water from the stomatal pores
of leaves. This is called the cohesion-tension model of water
transport. During daytime, the water lost through transpiration (by
the leaves to the surroundings) causes the guard cells and other
epidermal cells to become flaccid. They in turn take water from the
xylem. This creates a negative pressure or tension in the xylem
vessels, from the surfaces of the leaves to the tips of the roots,
through the stem. As a result, the water present in the xylem is
pulled as a single column from the stem. The cohesion and adhesion
forces of the water molecules and the cell walls of the xylem vessels
prevent the water column from splitting.
In plants,
transpiration is driven by several environmental and physiological
factors. The external factors affecting transpiration are wind,
speed, light, humidity, and temperature. The plant factors affecting
transpiration are canopy structure, number and distribution of
stomata, water status of plants, and number of open stomata. Although
transpiration causes water loss, the transpirational pull helps water
rise in the stems of plants. This helps in the absorption and
transport of minerals from the soil to the various plant parts.
Transpiration has a cooling effect on plants. It helps maintain plant
shape and structure by keeping the cells turgid. Transpiration also
provides water for photosynthesis.
In tall trees, water rises with the help of the transpirational pull generated by transpiration or loss of water from the stomatal pores of leaves. This is called the cohesion-tension model of water transport. During daytime, the water lost through transpiration (by the leaves to the surroundings) causes the guard cells and other epidermal cells to become flaccid. They in turn take water from the xylem. This creates a negative pressure or tension in the xylem vessels, from the surfaces of the leaves to the tips of the roots, through the stem. As a result, the water present in the xylem is pulled as a single column from the stem. The cohesion and adhesion forces of the water molecules and the cell walls of the xylem vessels prevent the water column from splitting.
In plants, transpiration is driven by several environmental and physiological factors. The external factors affecting transpiration are wind, speed, light, humidity, and temperature. The plant factors affecting transpiration are canopy structure, number and distribution of stomata, water status of plants, and number of open stomata. Although transpiration causes water loss, the transpirational pull helps water rise in the stems of plants. This helps in the absorption and transport of minerals from the soil to the various plant parts. Transpiration has a cooling effect on plants. It helps maintain plant shape and structure by keeping the cells turgid. Transpiration also provides water for photosynthesis.
