Question

Discuss all the steps (as per plant physiology) in detail that are involved from the absorption of water to the loss of water.

                                                                                                                                        

Answer 1

Answer- Root hairs are thin walled extensions of root epidermal cells that helps in absorption of water. As the water is absorbed by root hairs, it can follow two distinct pathways:-

a) Apoplast: it is the system big adjacent cell walls that is continuous throughout the plant except casparian strips of endodermis of roots. This movement of water occurs throught the intercellular spaces &the walks of cells and dependent on the gradient.

b) Symplast: it is the system of interconnected protoplasts. During this movement, water travels thriugh the cell cytoplasm or the intercellular movement is through plasmodesmata (cytoplasmic strands connecting neighbouring cells). The water enters through the cell membrane.

The water loss depends on the following factors:-

a) Root pressure- the ions from the soil gets actively transported into the vascular tissues of roots, water follows and increases the pressure inside the xylem, this positive pressure is called root pressure. It re-establish the continuous chains of water molecules in the xylem which breaks the tension created by transpiration.

b) Transpiration pull​​​- Transpiration is the evaporative loss of water by plants. It occurs through the stomata present on the leaves. When the turgidity of guard cells increases , the stomatal pores gets open and transpiration takes place. It depends on the following factors- cohesion, adhesion & surface tension.- these factors increases the capillarity of water (ability to rise in thin tube). During photosynthesis, the water evaporates through stomata (transpiration) . Since the thin film of water is continuous over cells, it results in pulling of water , molecule by molecule, into the leaf from xylem. This creates a transpirational pull.