Your assignment is to discuss what is going on in this graph

Your assignment is to discuss what is going on in this graph. Describe the relationship between the soil, the roots, and leaves as they pertain to water movement. I expect you to discuss these changes in terms of changes in water potential, diurnal fluctuations in activity, the nature of water integral the soil, and what is driving the changes in water potential.

Solution

The graph represents water pontential of soil, root (xylem) and leaf (mesophyll cells). Initially, the soil is wet which dries out with time and the soil water potential becomes more negative; at this point it is called as soil water tension also. The value -15 bar represents the wilting point which is the soil water content at which wilting of leaf can not be recovered upon watering. Roots also serve to remove the water from theirt adjacent surrounding soil particles and thereby lower down the water content (soil water potential) in that zone. The larger surface area of root hairs changes the osmotic pressure in the roots and allows the water to enter the roots down the potential gradiant. The water moves up in the xylem down the potential gradiant. For the purpose, capillary action moves the water droplet up in the xylem. Mesophyll water potential is reduced by transpiration. The resultant transpiration pull creates the negative mesophyll water potential and the water enters the leaves.