绿豆和大豆叶片光合作用对科尔沁沙地光照条件的响应

Respondence to High Radiation of Leaf Photosynthesis of Mungbean and Soybean in Horqin Sandy Land

运用LI-6400便携式光合作用测定系统比较科尔沁沙地大田种植的绿豆(Phaseolus radiatus L.)和大豆(Glycine max)两种豆科作物的净光合速率(Pn)、胞间CO2浓度(Ci)、气孔导度(Gs)的日变化;同时用便携式荧光仪(Handy-PEA)测定了PSⅡ最大量子效率(Fv/Fm)和PSⅡ最初电子受体QA的库容(Sm)的日变化。两种作物叶片净光合速率(Pn)的日变化曲线均为单峰曲线,峰值均在08:00;且08:00后绿豆叶片Pn均大于大豆。气孔导度在全天进程中一直呈下降趋势;分析表明:10:00—14:00Pn的降低的主要原因是非气孔因素。与大豆相比,光照强烈(>1 455μmol.m-2.s-1)的时段(08:00—14:00),绿豆能够更有效地调控Ci、Gs、Fv/Fm和Sm。另外,与7月下旬开花期研究结果相比,随着环境条件的变化和植物的生长发育期的不同,绿豆调节其光合适应对策:气孔调节能力增强,叶片对流经PSⅡ的电子传递的调控能力增强。因此,较高的适应强烈光照的能力和对环境条件变化快速响应的能力有利于绿豆在科尔沁沙地灌溉不便的雨养农田中进行广泛栽培。

Mungbean （Phaseolus radiatus L. ） and soybean （Glgcine max）, as two main leguminous crops are abroad cultivated in Horqin Sandy Land. LI-6400 Portable Photosynthesis System was used to study the characteristics of diurnal patterns of net photosynthetic rate （Pn）, intercellular CO2 concentration （Ci） and stomatal conductance （Gs） in leaves of mungbean and soybean. At the same time, the diurnal patterns of maximal quantum yield of photosystem II （ Fv/Fm ） and pool size （ Sm） of photosystem II primary electron acceptor （QA） in their leaves were measured with Handy-PEA. The two crops had apparent differences in their one-peak curves of Pn in the day course. The time when the peak values of their Pn occurred was similar at 8：00, and Pn in mungbean leaves was higher than that in soybean leaves after 8：00. It was suggested that mungbean could keep a higher Pn than soybean under high solar radiation （〉 1 455 μmol·m^-2·s^-1）. The stomatal conductance （Gs） in leaves of mungbean and soybean declined during the day, and did not show the ＂ noonbreak＂. It was not suggested that the stomatal factors contributed to the drop of Pn during 10 ： 00-- 14 ： 00. Compared with soybean, mungbean could effectively adjust intercellular CO, concentration （Ci）, stomatal conductance （Gs）, maximal quantum yield of photosystem II （Fv,/Fm） and pool size （ Sm） of photosystem Ⅱ primary electron acceptor QA, under high solar radiation （〉 1 455 μmol·m^-2·s^-1） during 8：00-- 14：00. Thus it could effectively adjust the degree of stomatal opening and photo inhibition, controlled the electron transport and dissipated reductant energy absorbed by chlorophy Ⅱ . It was suggested that Mungbean had higher capacity of adaptation to high radiation than soybean. In addition, compared with the study result acquired in the last ten-day of July, Mungbean regulated its counter- measure of photosynthetic adaptation, the limit of stoma limited photosynthesis less but the leaves had higher capacity to regulate the reduction state of QA, thus restricting the electron transport more effectively through photosystem II . As a result of the capacity of higher adaptation to high radiation and the quick responses to the environmental changes, it favors that Mungbean can be abroad cultivated in the non-irrigated crop land in Horqin Sandy Land.