干旱对高产小麦宁麦9号旗叶光合特性的影响

Effects of drought on photosynthetic properties in flag leaves of a high-yield wheat variety Ningmai 9

通过土壤自然干旱法,以共有一亲本但产量较低的宁麦8号为对照,研究了高产小麦宁麦9号旗叶光合特性。结果表明,土壤相对含水量RWCS、叶片相对含水量RWCL、净光合速率Pn、气孔导度gs、蒸腾速率E以及叶肉导度gm在整个自然干旱过程中不断降低;在干旱前8d,胞间CO2浓度Ci降低,水分利用效率WUE增加,而在干旱的8～12d,Ci增加,WUE降低。Pn与gm的变化呈显著的正相关(R2=0.938,P<0.0001),而与gs无明显的相关性。因此,在土壤干旱胁迫下,叶肉导度gm是抑制Pn的主导因素,而gs的影响较小。和宁麦8号相比,宁麦9号具有较高的Pn、gs、gm、WUE和较低的E。因此,较高的光合能力、水分利用效率以及较强的抗旱性可能是宁麦9号高产的生理基础,而其抗旱性强可归结为水分利用效率较高。

The experiment was conducted under drought condition (water withholding) to investigate the photosynthetic parameters in flag leaves of the high-yield wheat (Triticum aestivum L.) varieties Ningmai 9, using Ningmai 8 as control. The results showed that in the course of water withholding, there were constant decreases in relative water content of soil (RWC_S), leaf relative water content (RWC_L), net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (E), and mesophyll conductance (g_m, calculated as the ratio of P_n to C_i). During 0~8 d of water withholding, subcelluar CO_2 concentration (C_i) decreased and water use efficiency (WUE) increased, whereas during 8~12 d of water withholding, C_i increased and WUE decreased significantly. There was a close positive correlation between P_n and g_m(R^2=(0.938,) P<0.0001), but no clear correlation between P_n and g_s was observed. It could be concluded that under both mild and serious drought conditions, non-stomatal limitation may be the primary factor to inhibit photosynthesis, rather than stomatal conductance. Compared with Ningmai 8, Ningmai 9 had a higher P_n, g_s, g_m and WUE, and a lower E. Moreover, drought induced a slower decrease in P_n in Ningmai 9 than in Ningmai 8, indicating a stronger drought-resistance in the former. Therefore, the properties of high photosynthetic capacity, WUE and drought-resistance may be the physiological basis of high-yield in Ningmai 9, whose drought-resistance could be attributed to the high water use efficiency.