Question

Describe the transpiration pull model of water transport in plants. What are the factors influencing transpiration? How is it useful to plants?

Answer 1

With the aid of the transpiration pull produced by transpiration or loss of water from the stomatal pores of leaves, water increases in tall trees. This is called the water transport cohesion-tension model.

Complete Step by Step Answer: The water lost by transpiration (through the leaves to the environment) throughout the day allows the guard cells and other epidermal cells to become flaccid. They take water from the xylem in exchange. In the xylem vessels, this induces a negative pressure or stress from the surfaces of the leaves to the tips of the roots, via the stem. The water present in the xylem is then pulled from the stem as a single column. The water molecules and the cell walls of the xylem vessels' cohesion and adhesion forces prevent the water column from separating.
In plants, many environmental and physiological factors drive transpiration.
Wind, speed, light, humidity, and temperature are the external factors influencing transpiration.
The canopy structure, number and distribution of stomata, water status of plants, and a number of open stomata are the plant variables influencing transpiration.
While water loss is caused by transpiration, the transpiration pull helps to increase water in plant stems. This helps to absorb and transfer minerals from the soil to the different components of the plant.
On plants, transpiration has a cooling effect. By holding the cells turgid, it helps preserve plant shape and structure. For photosynthesis, transpiration often provides water.

Note: In leaves that are stiff with turgor (water pressure), the transpiration rates are maximum. They give less surface area to sun exposure as leaves wilt, and therefore will transpire less, saving water. For a demonstration of this water-saving technique, observe a tough, drought-tolerant plant like lilac when temperatures are high. Succulents conserve water by opening the pores of the stomata at night to minimize transpiration and to take in carbon dioxide contained in their leaves before they can photosynthesize the next day. By covering the pores of the stomata, anti-transpirant products, such as Wilt-Pruf, can decrease transpiration, but that also restricts photosynthesis.