Respiration and Nutrient Absorption of Plant Roots Growing under Aerobic or Anaerobic Condition : 2. Respiration and nutrient absorption of rice roots growing under aerobic condition

Abstract

Attached roots and detached roots of rice plants were examined for the rates of respiration and nutrient absorption under an aerobic condition, adopting the methods stated in the previous reports. The results obtained may be summarized as follows; 1. There were no marked differences in the rates of respiration and nutrient absorption of attached roots whether they were kept under an aerobic condition or not. 2. When detached roots were exposed to an aerobic coditon, they carried on almost normal respiration being followed by promotion of nutrient uptake, comparing with those exposed to an anaerobid condition. But they took up less amount of nutrients than attached roots in spite of the rate of respiration being rather accelerated. That may be the reason why detached roots were kept under conditions disadvantageous to nutrient absorption, as stated in the previous report. Besides, some othe reason was considered. 3. In case NaN3 was added to the culture solution, the rates of respiration and nutrient uptake both of attached and detached roots were severely depressed even if they were kept under an aerobic condition. 4. Attached roots showed a strong oxidizing power whether they were kept in an aerated or nonaerated medium. In contrast the oxidizing power of detached roots was decreased markedly when they were kept in a non-aerated medium, although they could reveal an oxidizing power as strong as that of attached roots when kept in an oxygenated medium. The oxidizing power of both kinds of roots which had been grown in the culture solution containing NaN3 was always depressed whether they were kept in an aereted mediun or not. 5. From the results stated above as well as those reported in the previous papers, it may be concluded that the roots of rice plants can perform almost normal respiration and nutrient absorption even if they are exposed to a poorly oxygenated medium so for as no substances harmful to respiration are present there. Because the rice roots can receive molecular oxygen enough to sustain aerobic respiration from the the tops through the well-developed ventilating system.