Relationship between Resistance to Water Transport and Exudation Rate and the Effect of the Resistance on the Midday Depression of Stomatal Aperture in Rice Plants

Japanese Journal of Crop Science

Tadashi HIRASAWA¹  Masanori TSUCHIDA¹  Kuni ISHIHARA¹ 

关键词: Active water uptake;    イネ;    Exudation rate;    気孔開度;    Midday closure of stomata;    気孔の日中閉鎖;    Passive water uptake capacity;    出液速度;    Resistance to water transport;    受動的吸水能力;    Rice plants;    蒸散;    Stomatal aperture;    水の通導抵抗;    Transpiration;    能動的吸水能力;   

DOI  :  10.1626/jcs.61.145

学科分类：农业科学（综合）

来源: Nihon Sakumotsu Gakkai / Crop Science Society of Japan

【 摘 要 】

There was considerable difference in the degree of the midday depression in the stomatal conductance, and the photosynthetic rate among rice plants grown under different conditions, and the degree of the midday depression was supposed to depend on root-water uptake ability. The present study was conducted to investigate the difference in the exudation rate under practically zero transpiration, representing active water uptake capacity, and in the resistance to water transport under intense transpiration, representing passive water uptake capacity, among rice plants grown under different conditions. The relationship between passive and active water uptake capacities as well as between the passive water uptake capacity and the degree of midday stomatal closure was also investigated. In the plants in which "root-rot" occurred as a result of the soluble starch added to the soil and in those which were grown under the conditions of low light intensity and high humidity and developed a smaller root system, the exudation rate was low and the resistance to water transport was high compared to the control plants. This means that active and passive water uptake capacities were lower in these plants than in the control plants. In the plants which were grown on the culture solution of low nitrogen level and developed larger root system, exudation rate was high and the resistance was low compared to the plants grown on the standard culture solution, that is, active and passive water uptake capacities were higher in the former than in the latter. The degree of the midday depression in the stomatal aperture was larger in the plants in which resistance to water transport was larger and there was a close correlation between the resistance, i.e. passive water uptake capacity, and the degree of the midday depression. On the other hand, in the plants whose leaf nitrogen content was increased by applying ammonium sulfate one week before measurement commenced, exudation rate increased markedly but the resistance to water transport did not change. The stomatal aperture was far larger in the plants supplied with additional ammonium sulfate than in the control plants in the morning, but the difference in the sizes of these respective stomatal apertures became smaller under intense midday transpiration because of the absence of any difference in their passive water uptake capacities. In view of the high correlation between gas exchange rate through stomata and photosynthetic rate, these results suggest that higher passive water uptake capacity is essential, in addition to the increase in leaf nitrogen content, in increasing the daily total photosynthesis.

【 授权许可】

Unknown