干旱和复水对大豆(Glycine max)叶片光合及叶绿素荧光的影响

Effects of drought and rewatering on photosynthesis and chlorophyll fluorescence of the soybean leaf

选用河南省大面积种植的大豆品种豫豆29作为实验材料,通过研究逐步干旱和旱后复水条件下大豆叶片光合、叶绿素荧光等指标随土壤水分的动态变化规律,以期为大豆的水分高效利用提供理论依据。研究发现,在土壤相对含水量高于46.5%时,虽然随着土壤相对含水量的下降,豫豆29仍可以保持它的叶片水分状态;豫豆29的叶片净光合速率在土壤水分中等条件下最大,在土壤相对含水量为64.3%时,它比对照组高出11.2%(P<0.01);在实验的第3d,处理组的土壤相对含水量降为46.5%,叶片水势与对照组相比降低了7.2%(P>0.05),净光合速率为对照组的89.6%(P<0.05),但气孔导度却迅速下降为对照组的44.7%(P<0.01),这说明与叶片的光合和水分状况相比,豫豆29的气孔对土壤水分的匮缺更加敏感。复水后,豫豆29叶片的水势、净光合速率、气孔导度和叶绿素荧光等值都可以得到迅速的恢复,并在实验的最后接近对照组的水平,这表明豫豆29的叶片光合在水分胁迫解除后有迅速恢复的能力。

The leaf photosynthetic rate, A, of higher plants is known to decrease as the relative water content and leaf water potential decrease. The most sensitive indicator of overall physiological state of plant is often stomata behavior, The controversy continues as to whether drought mainly limits photosynthesis through stomata closure or through metabolic impairment. Evidence that impaired ATP synthesis is the mainly factor limiting photosynthesis even under mild drought has further arose debate. Currently, many transgenic crops, mainly in wheat, have been achieved, and they exhibited a drought resistance to some extent. But they all have some shortage related to agronomical performance and/or development. These results show that systemic, deeper, and comprehensive understanding of physiological mechanism of crops under drought stresses is not enough. A soybean variety widely cultivated in Henan Province, Glycine max cv. yudou29, was selected as the experimental material. The endeavor is aimed at providing a theoretical basis for high efficient water use in soybean cultivation, by studying the dynamic changes of photosynthesis and various physiological factors in the process of drought and rewatering. The experiment began at the pre-flower stage of the soybean and lasted 9 days. The research shows that when SRWC （soil relative water content） of group t was higher than 46.5 %, leaf water potential of Glycine max cv. yudou29 was unaffected by SRWC. Net photosynthesis rate of the leaf appeared to peak when SRWC was moderate： at 64.3%, net photosynthetic rate of group t was 11.2% higher than that of CK （P 〈 0.01 ）. On the third day, when SRWC of group t was 46.5%, leaf water potential of this group was 7.2% lower than that of the CK（ P 〉 0.05 ）, and net photosynthesis ratio of this group was 89.6% of that of the CK （P 〈 0.05 ）, while gs rapidly dropped to 44.7% of that of the CK （P 〈 0. 01 ）. This shows that gs was more sensitive to soil water deficiency than photosynthesis and leaf water potential. After rewatering, the leaf water potential, net photosynthesis rate, gs and chlorophyll fluorescence parameters were all recovered quickly, and approached to the level of the CK by the end of the experiment. This indicates that the Glycine max cv. yudou29 leaf photosynthesis has the ability to rapidly recover from drought once the stress is released.