Effects of Isosmotic Concentrations of Inorganic and Organic Substrates on Entry of Water into Corn Roots

Publisher Website
Google Scholar
Abstract
Using a potometric device previously described, the rate of intake of water into intact corn roots (Mexican June var.) was detd. under conditions of constant temp. and rel. humidity with the following substrates at osmotic pressures indicated: base nutrient soln. (0.8 atm.); b.n. + Na2SO4, b.n. + NaCl, b.n. + CaCl2, (2.8 and 4.8 atm.), mannitol and sucrose (0.8, 2.8, 4.8 atm.); and sucrose (6,8 atm.). The data indicate that total osmotic pressure of the substrate is a primary factor limiting entry of water but it is recognized that the character of the solute and toxicity of salts or ions may also affect rate of intake. Compared with 0.8 atm. substrates, the reduction in rate at 4.8 atm. varied only 3% (79-82%) regardless of the solute used. Sucrose at 6.8 atm. completely inhibited intake. Differences in the average mean rate of intake between the 0.8, 2.8 and 4.8 levels of osmotic pressure were highly significant with all substrates. The relation of these data to practical problems of irrigation agriculture, in saline areas is discussed. It would appear that water is not equally available between field capacity and the wilting range and that both the force with which water is held by the soil particles and the amt. of soluble salts present in the soil soln. are important factors when considering water available to plants.