EFFECTS OF OXYGEN CONCENTRATION ON THE RESPIRATION OF EXCISED ROOT-TIP SEGMENTS OF MAIZE AND RICE, AND OF GERMINATING GRAINS OF RICE AND BUCKWHEAT

In view of the known tolerance of rice (Oryza sativa) to wet soils, in contrast to maize (Zea mays), a comparison of the respiratory responses of the two plants to different O2 concen trations was made. It was found that if the O2 concentration was raised to 100%, an increase was observed of the O2 input and the CO2 output in maize root‐tip segments and in germinating grains of rice and also in buckwheat (Fagopyrum sp.). In marked contrast rice root‐tip segments, when treated with 100% O2, exhibited no such increase over the air controls. Increased O2 concentrations decreased RQ values ranging from 2.0 (with 5% O2) to 0.86 (with 100% O2). Air‐control RQ values were lowest with maize roots (0.9) and highest with germinating rice grains (1.0). Rice grains also exhibited the highest F/R ratio (0.85), and buckwheat grains the lowest (0.45). The addition of sucrose to maize root tips tended to promote fermentation (CO2 output) rather than aerobic respiration (O2 input). Copyright © 1979, Wiley Blackwell. All rights reserved