Fundamental studies on the actual condition of heat stress and its avoiding mechanism in crop plants

为了弄清高温胁迫下的实际情况，利用热跟踪仪对部分作物叶片温度的实时变化进行了可视化跟踪，并分析了其与气孔开度、蒸腾速率和光合速率的关系。主要结果如下：1.春小麦旗叶的气孔近轴面多于远轴面，远轴面气孔开闭运动较钝。在白天，菜豆叶片表面温度的变化与气温变化基本平行，与蒸腾速率变化同步，且远轴面温度高于近轴面温度。随叶片倾角的变化而变化，表明叶片的太阳跟踪运动在避免热胁迫中起着重要作用。而在非水分胁迫条件下，无论叶片倾角如何，叶片远轴面温度都相对稳定.在干湿两种土壤水分条件下，对不同根质量的马铃薯品种“农林1号”（大）和“小冬”（小）进行了栽培试验，分析了根质量和土壤水分条件对叶温的影响。干地的叶温高于湿地，干地与湿地的叶温之差Konafubuki为3.3 ℃，Norin 1为2.2 ℃。叶温随气温的升高而线性升高，与蒸腾速率呈负相关。在高气温条件下，由于水分胁迫，植株气孔关闭，光合速率下降。

In order to clarify the actual condition of heat stress, the realtime changes of leaf temperature in some crop plants were tracked visually by using thermotracter and analyzed its relations with stomatal aperture, transpiration rate and photosynthetic rate. The main results obtained were summarized as follows ;1.The flag leaf of a spring wheat (var.Haruyutaka) had more stomata on adaxial side than on abaxial side, and the opening and shutting movement of stomata were dull on abaxial side. In the daytime, the leaf surface temperature changed almost parallel with the changes in air temperature, accompanied with transpiration rate, and higher on abaxial side than on adaxial side.2.The leaf surface temperature of adaxial side of kidney bean (Phaseolus vulgaris L.) changed with changes in the leaf inclination, suggesting that the solar tracking movement of leaf plays an important role on the avoiding of heat stress. However, the leaf surface temperature of abaxial side were relatively stable regardless of leaf inclination under non-water stress conditions.3. The two potato varieties with different root mass, Norin 1 (large) and Konafubuki (small), were grown under two soil water conditions, wet and dry, and analyzed the effect of root mass and soil water conditions on leaf temperature. The leaf temperature was higher in dry plot than in wet plot, and the differences of leaf temperature between wet and dry plots was 3.3ﾟC for Konafubuki and 2.2ﾟC for Norin 1. The leaf temperature increased linearly with the increase in air temperature, accompaning with transpiration rate. The photosynthetic rate decreased because of the closing of stomata, due to water stress in plant under high air temperature conditions.