Effect of osmotic pressure on root growth,cell cycle and cell elongation

Summary The paper reports a study of root growth, the duration of the cell division cycle and cell size, inAllium cepa roots grown in mannitol solution, with osmotic pressures of 0–16 atm., at 25° C, with aeration. Root growth decreases markedly as the osmotic pressure rises, at 12 atm. being about 35% of what it is at 0 atm. The rate of the cell cycle, , expressed as the percentage of cells passing through any given point in the cycle in one hour, is a roughly linear function of the osmotic pressure, and at 12 atm. is reduced to 80% of what it is at 0 atm. The reaction of the cell size to osmotic pressure is similar to that of the growth. The relative values of the two diverge progressively as the osmotic pressure increases and at 12 atm. the elongation of the cells has dropped to 40% of normal.The data obtained agree with those given by the equationG = K · · L, in whichK is a constant, is the rate of the cycle (reciprocal of its duration) andL the average size of the mature epidermal cells.