玉米/花生间作行比和施磷对玉米光合特性的影响

试验于2014—2015年设玉米/花生间作2∶2(R₁)、2∶4(R₂)和2∶8(R₃)三种间作模式,研究了间作行比和施磷对玉米冠层光照日变化、功能叶的SPAD值、光合-光强响应曲线和光合-CO₂响应曲线的影响,以探究间作玉米适应强光的光合机理.结果表明: 间作玉米冠层日均光照表现为R₃>R₂>R₁;大口期至灌浆期,间作玉米穗位叶的SPAD值、表观量子效率(AQY)、光补偿点(LCP)、光饱和点(LSP)、光饱和时的最大净光合速率(LSP_n)、羧化效率(CE)、最大电子传递速率(J_max)、磷酸丙糖利用率(TPU)、气孔导度(g_s)、蒸腾速率(T_r)和净光合速率(P_n)均表现为R₃>R₂>R₁,胞间CO₂浓度(C_i) 则为R₁>R₂>R₃;蜡熟期R₃间作玉米的AQY、LSP_n、g_s、CE、J_max和TPU均低于R₂间作玉米;施磷能提高AQY、LSP_n、CE、V_{c max}、J_max和TPU等光合参数.这说明间作玉米g_s、AQY、CE、V_{c max}、J_max和TPU随着光强增加逐渐提高是其增强利用强光能力的关键,但超过一定光强易早衰,施磷肥有助于增强玉米对强光的利用和延缓叶片衰老.

Effects of maize/peanut intercropping row ratio and phosphate fertilizer on photosynthetic characteristics of maize.

To get better insight into the photosynthetic mechanism of plant adaptation to strong light in intercropped maize, a field trial was carried out in 2014-2015 to investigate the effects of maize/peanut intercropping row ratio and phosphate fertilizer on diurnal variation in light intensity of maize canopy, SPAD value, and the curves of photosynthetic response of net photosynthetic rate (P_n) to photon flux density (PFD) and to CO₂ of functional leaves. The field trial comprised 2 rows maize intercropped with 2 rows peanut (2:2, R₁), 2 rows maize intercropped with 4 rows peanut (2:4, R₂) and 2 rows maize intercropped with 8 rows peanut (2:8, R₃). Results showed that the light intensity of intercropped maize canopy was R₃>R₂>R₁. From pre-tasselling to filling stage, the SPAD value, apparent quantum efficiency (AQY), light compensation point (LCP), light saturation point (LSP), maximum net photosynthetic rate, carboxylation efficiency (CE), maximum electron transfer rate (J_max), triose phosphate utilization (TPU), stomatal conductance (g_s), transpiration rate (T_r) and P_n in ear leaves of intercropped maize were R₃>R₂>R₁, but the intercellular CO₂ concentration (C_i) was R₁>R₂>R₃. At dough stage, the AQY, LSP_n, g_s, CE, J_max and TPU in ear lea-ves of intercropped maize in R₃ intercropping system were lower than those in R₂ intercropping system. The photosynthetic indices, such as AQY, LSP_n, CE, V_{c max}, J_max and TPU were increased by phosphate fertilizer application. These results suggested that the key mechanisms that enhanced strong light utilization ability of intercropped maize were attributed to gradual improvement in g_s, AQY, CE, V_{c max}, J_max and TPU of ear leaves with increasing light intensity, however, beyond a certain light intensity, intercropped maize leaves were prone to premature senescence. Nonetheless, phosphate fertilizer could improve light utilization and delay leaf senescence in intercropped maize.