ABSTRACT Crop leaves growing under field conditions experience fluctuating light intensities. The photosynthetic response to a sudden increase in light intensity, which is termed the photosynthetic induction response, can potentially affect crop productivity. In the present study, the genetic variation in the photosynthetic induction response and the related gas exchange parameters in the rice diversity research set of germplasm (RDRS) were evaluated using two reference genotypes: Koshihikari and Takanari. Takanari is known to show superior induction response than Koshihikari. The photosynthetic induction response was found to be highly diverse in 59 rice genotypes. The cumulative CO2 fixation during the first 10 minutes after a transition from low to high light intensity (CCF10) differed by a factor of four between genotypes. The variation of CCF10 showed no relationship with light saturated photosynthetic rate (R = 0.21), but was significantly correlated with photosynthetic rate (A) under low light conditions (R = 0.88). Several genotypes showed even more rapid induction responses than that of Takanari. In particular, A of ARC 11094 and Rexmont both increased rapidly during the first two minutes of the induction response. The CCF10 of these two genotypes was approximately four times greater than that of Koshihikari. The rapid induction responses of Rexmont and ARC 11094 most likely resulted from the activation of CO2 fixation in mesophyll cells and CO2 diffusion from the air to the leaves, respectively. This study demonstrates that there is a large genetic variation in and, therefore, much potential for genetic improvement of, the photosynthetic induction response in rice.

中文翻译：

---

水稻（Oryza sativa L.）光合诱导反应的遗传变异

摘要 在田间条件下生长的作物叶子会经历光强波动。对光强度突然增加的光合反应，称为光合诱导反应，可能会影响作物生产力。在本研究中，使用两个参考基因型：Koshihikari 和 Takanari，评估了水稻种质多样性研究集 (RDRS) 中光合诱导反应的遗传变异和相关的气体交换参数。众所周知，Takanari 表现出比 Koshihikari 更好的诱导反应。发现光合诱导反应在 59 个水稻基因型中高度多样化。在从低光强度到高光强度 (CCF10) 过渡后的前 10 分钟内，累积的 CO2 固定在基因型之间相差四倍。CCF10的变化与光饱和光合速率（R = 0.21）无关，但与弱光条件下（R = 0.88）光合速率（A）显着相关。几种基因型显示出比 Takanari 更快的诱导反应。特别是，ARC 11094 和 Rexmont 的 A 在诱导反应的前两分钟内都迅速增加。这两种基因型的 CCF10 大约是 Koshihikari 的四倍。Rexmont 和 ARC 11094 的快速诱导反应最有可能分别是由于叶肉细胞中 CO2 固定的激活和 CO2 从空气向叶片的扩散。这项研究表明，存在很大的遗传变异，因此，遗传改良的潜力很大，