Transpiration and Photosynthesis Characteristics of the Panicle in Comparison with the Flag Leaf in the Rice Plant

[摘要] This study was conducted to clarify photosynthesis and transpiration characteristics of the panicle in comparison with the flag leaf in the rice plant, cultivar Nipponbare. Transpiraion rate in the panicle was the maximum at heading time, decreasing with aging in the panicle. There was a slight difference in diffusive conductance between the light and dark. Transpiraion rate in the panicle increased linearly as vapor pressure difference increased, and there was no difference in the slopes of the straight lines between the light and dark. Diffusive conductance of the flag leaf in the dark was one tenth of that in the light. In the dark it was half of that in the panicle. Apparent photosynthesis and dark respiration rates of the panicle attained the maximum in five and ten to fifteen days after the heading time, respectively. The maximum rate of gross photosynthesis of N the panicle was about 6 mg CO2 dm-2hr-1, which was one sixth of gross photosynthetic rate in the flag leaf. Furthermore, dark respiration rate was equal to the apparent photosynthetic rate in the panicle and it was higher than dark respiration rate in the flag leaf. Diffusive conductance and photosynthetic rate of the flag leaf decreased with increasing in vapor pressure difference. Since diffusive conductance and photosynthetic rate in the panicle did not change with increasing vapor pressure difference, it was thought that they were not affected by vapor pressure difference. It was considered from our experimental results and the other previous results in the panicle morphology that gas exchange of transpiration and photosynthesis in the panicle hardly took place through the stomata. The panicle was divided into the spikelets and the rachis-branches (including rachis), and their transpiration and photosynthetic rates in the light and dark were measured. The results showed that the characteristics of transpiration and photosynthesis in the panicle were mainly contributed by those of the spikelets.

[学科分类] 农业科学（综合）

[关键词] Dark respiration;暗呼吸;Leaf;イネ;Panicle;æ°—å­”;Photosynthesis;光合成;Rice;蒸散;Stomata;ç©‚;Transpiration;葉身