Question

Answer following questions:

a). describe in details that what cells, tissues, and organs are involved in the movement of water from roots to leaves.

b). the cause for plants wilting

c). the features of plants that reduce water loss

d). Explain the relationship between the cohesion-tension mechanism and water potential gradient

Answer 1

a)

water is absorbed via root hair cells and moves via diffusion to Xylem tissue, Xylem has cells called tracheids and vessels which transport water vertically. Vessels even have pits for horizontal transfer of water. xylem tissue is present in veins of leaves and is connected with stem tissues and in this way water reaches the leaves

b) Excess of evaporative loss of water from leaves via transpiration decreases the turgor pressure exerted by plants on the cell walls. if the transpiration rate exceeds that of absorption of water by plants, the loss cannot be made up. In this case, it causes wilting.

c)

plants have various features that prevent loss of water. Leaves might have thick cuticle. They may also have a waxy coating. Stomata are the major opening in leaves that form the portal of transpirational loss. Hence several plants have fewer stomata. At times leaves may be also reduced to spines. A decreased surface area reduces evaporation to much extent.

d) water diffuses from mesophyll cells to adjacent air spaces drawn by transpiration. This deficiency of water on the surface of mesophyll cells creates a tension which in turn pulls water from the xylem which has a relatively higher water potential. Cohesion among water molecules helps it being pulled up the xylem against gravity under transpiration loss aided by water potential gradient (roots having higher water potential than leaves)