热胁迫对希蒙得木幼苗光合特性的影响

3种处理温度(CK、T1、T2),全天平均温度分别为31℃、38℃和46℃,最高温度分别为35℃、44℃和54℃。T1处理希蒙得木的Pn日变化曲线呈双峰型,峰值分别出现在10:00和16:00,表现出光合"午休"现象;T2处理的Pn日变化从8:00到10:00持续下降,10:00时Pn为-1.87μmol CO2.m-2.s-1,从10:00到18:00,Pn基本没有变化。不同温度处理希蒙得木叶片的最大净光合速率(Pn)差异显著,CK处理的Pn是T2处理的2.26倍,T1处理的Pn是T2处理的1.41倍;随着胁迫强度的增加,希蒙得木的Tr不断下降,CK处理下希蒙得木日平均Tr为T2的3.66倍,表明希蒙得木是一种比较耐热的植物。希蒙得木LSP和LCP降低,是其适应高温逆境的一种重要形式。3种温度处理下希蒙得木光能利用效率(SUE)表现为CK和T1处理的SUE在10:00最高;T2处理的以8:00最高,其余均为负值。从全天来看,CK、T1、T2处理的SUE平均为7.06%、5.13%、0.41%。

Effect of Heat Stress on Photosynthetic Characteristics of Simmondsia chinensis Seedlings

Three kinds of treatment （ CK, T1 and T2）, the average temperatures were 31℃ ,38℃ and 46℃. The highest temperatures were 35℃ ,44℃ and 54℃. The daily change of Pn was bimodal under T1 treatment, the seedling showed ＂ midday depression＂ phenomenon. The peak values occurred at 10：00 and 16：00. The diurnal variation of Pn from 8：00 to 10：00 continually decreased when the seedlings were treated at T2. Pn was - 1.87 μmolCO2·m^-2·s^-1 at 10：00,and no changing occurred from 10：00 to 18：00. Different temperatures made the maximum net photosynthetic rate （Pn） obviously different,The Pn under the CK treatment was 2. 26 times as high as under the T2 treatment, Pn under the T1 treatment was 1.41 times more than under the T2 treatment. With the increment of stress degree, Tr of S. chinensis was deseending, the average of Tr under CK was 3.66 times more than under T2, indicating that S. chinensis was a heat tolerance plant. LSP and LCP decreasing were an important form to suit the heat adversity. SUE of CK and T1 was the highest under three temperature treatments at 10：00. T2 treatment was the highest at 8：00, the others were minus values. The average SUE of CK,T1 ,T2 was 7.06%, 5. 13% and 0.41%.