EFFECTS OF OXYGEN TENSION ON CERTAIN PHYSIOLOGICAL RESPONSES OF RICE, BARLEY, AND TOMATO

Abstract

The relation of oxygen pressure to some metabolic processes of plants has been examined in recent experimental work with particular reference to the energy requirements of active cells. The reactions studied under the most carefully controlled conditions are accumulation of salt and respiration by excised roots and storage organs. This is particularly true of the work by Hoagland and his associates at the University of California, and Steward at the University of London. Other investigations have been concerned with the response of entire plants to oxygen deficiency in the roots. Earlier studies compared plants grown in submerged soils with those grown in well-drained soils. It is evident that the control over such experiments is complicated by the influence of several variables such as carbon dioxide pressure, accumulation of anaerobic products, and the intervention of microbiological activity. Greater control has been possible when water cultures have been employed, exposing the root systems to continuous streams of air or relatively pure nitrogen. The influence of oxygen supply on tomato, buckwheat, barley, lupine, and other plants has been studied in this way. The oxygen relations of the rice plant present a particularly interesting and important problem since as a crop it is grown under conditions (apparently anaerobic) which inhibit the growth of many field plants. This ability of rice to thrive in submerged soil has been observed and confirmed by some research workers and denied by others. A rather large number of diverse experiments on a qualitative scale has left suspended a final estimation of the capacity of rice, real or apparent, to grow in an anaerobic root environment.