Q.The water used by plants is:

Kramer (1949) distinguished two independent mechanisms by which roots take up water. Active absorption is powered by forces generated inside the root itself, and comes in two forms: osmotic active absorption (Atkins, 1916; Priestley, 1923), in which hypotonic soil water is imbibed by the root-hair cell wall and then drawn in by osmosis because the cell sap is hypertonic to it, with the resulting pressure at the protoxylem recognised as root pressure - though this theory struggles because xylem sap concentration is not always high and root pressure is not universal, especially in trees; and non-osmotic active absorption (Bennet-Clark, 1936; Thimann, 1951; Kramer, 1959), in which water is absorbed even against the soil-to-cell-sap concentration gradient, using energy released by root respiration, as shown by the fact that respiratory inhibitors like KCN and chloroform reduce water uptake. Passive absorption, by contrast, gives the root no active role at all - it is d …