玉米叶片光合作用和渗透调节对干旱胁迫的响应

以2个不同抗旱性玉米品种郑单958 (抗旱性强)和陕单902 (抗旱性弱)为材料，采用盆栽控水试验，设置3个干旱处理(轻度干旱、中度干旱、重度干旱)和正常灌水，研究了干旱胁迫对2个玉米品种气体交换、叶绿素荧光参数和渗透调节物质的影响。结果显示, 重度干旱造成2个玉米品种叶片光合机构紊乱，破坏细胞膜完整性；同时增加了渗透调节物质，这对增强叶片的保水能力，维持光合速率有重要的作用。但与陕单902相比，干旱胁迫下郑单958表现出较高的最大净光合速率(P_nmax)，表观量子效率(AQY)，光饱和点(LSP)，最大电子传递速率(J_max)，最大羧化速率(V_cmax)，PSII的实际量子产量(Φ_PSII)和光化学猝灭系数(q_P)；较高的脯氨酸(Pro)和可溶性糖含量(SS)；较低的丙二醛含量(MDA)。这些结果表明，干旱胁迫下抗旱品种郑单958具有较强的渗透物质能力，减轻细胞膜质过氧化程度，维持较高的光合性能是其适应干旱环境的生理基础。

Responses of Drought Stress on Photosynthetic Trait and Osmotic Adjustment in Two Maize Cultivars

The responses of gas exchange, chlorophyll fluorescence parameters and osmotic adjustment were studied in two different maize hybrids Zhengdan 958 (drought resistance) and Shaandan 902 (drought sensitive) under three different drought stresses (mild drought, moderate drought, severe drought) and normal irrigation in pot experiment. The results showed that drought stress caused disorder in photosynthesis, damage in the integrity of cellular membranes and increase the amounts of osmotic active substance (proline and soluble sugar) in both two cultivars. Thus these may have an important role in acclimation process to drought stress. However, compared with drought-stressed Shaandan 902, drought-stressed Zhengdan 958 showed higher values of maximum leaf net photosynthetic rate (P_nmax), apparent quantum efficiency (AQY), light saturation point (LSP), maximum rate of electron transport driving RuBP regeneration (J_max), maximum rate of RuBP carboxylatuin (V_cmax), PSII actual quantum yield (Φ_PSII) and photochemical quenching (q_P); higher contents of soluble sugars and proline and lower content of MDA. These results indicate that Zhengdan 958 have a better self-protection of photosynthetic system, greater accumulation of substances for osmotic adjustment for eliminating the negative effects on cellular membranes may be the major physiological traits in the adapt ability to drought conditions.