Photosynthetic characteristics in rice plants grown under the conditions of low temperature and irradiance.

在日本的北方地区，夏季的凉爽天气损害不仅是由于低温，而且还由于日照不足。在这样的天气条件下，光合作用受到强烈抑制。然而，很少有人知道，在这种条件下的生长如何影响光合作用在一个单一的叶片和整个plant.The光合特性和植物生长水平的研究水稻植株生长在白天/夜间温度为20/18摄氏度和辐照度为350 μ mol量子m-2 s-1的低温/辐照处理。在20 ℃下测定的光合速率在低温/光照条件下生长的水稻比在25/20 ℃和1000 mumol m^ s^下生长的水稻稍高<-2><-1>，而在25 ℃下测定的光合速率在这两种方式下生长的水稻之间没有差异。这种差异被认为是由于在低温/光照下生长的植物中RuBP再生能力略有增强造成的。在低温/光照条件下生长的植株，其相对生长率（RGR）明显降低，这是由于净同化率（NAR）降低所致。LAB（叶面积比）略大。因此，我们得出结论，虽然水稻植株能够部分适应低温和低光照条件，但在这种条件下，光合作用受到抑制直接导致生物量减少。

In the northern area of Japan, cool weather damage in summer is always caused not only by low temperature but also by a shortage of sunshine. Under such weather conditions, photosynthesis is : strongly suppressed. However, little is known about how growth under such conditions affects photosynthesis at the level of a single leaf and the growth at the level of the whole plant.The photosynthetic characteristics and plant growth were examined in rice plants grown at a day/night temperature of 20/18ﾟC and an irradiance of 350 mutmol quanta m-2 s-1 as the low-temperature/irradiance treatment. The photosynthetic rate measured at 20ﾟC was a little higher in rice grown under low-temperature/irradiance than in rice grown under 25/20ﾟC and 1000 mumol m^<-2> s^<-1>, whereas there was no difference in the photosynthetic rate measured at 25ﾟC between rice grown in these two ways. This difference was suggested to be caused by a slightly enhanced RuBP regeneration capacity in the low-temperature/irradiance-grown plants. The RGR (relative growth rate) were much smaller in the low-temperature/irradiance grown plants, and it was caused by a decreased NAR (netassimilation rate). The LAB (leaf area ratio) was slightly greater. We, thus, concluded that although rice plants are partially able to acclimate to the conditions of low temperature and low irradiance, the suppressed photosynthesis under such conditions directly leads to a decreased biomass production.