林药复合系统林下植物光合特性对生长光强的响应

以上海市松江不同郁闭度(低、中、高)生态公益林—— 香樟(Cinnamomum camphora)林下种植的红茴香(Illicium henryi)和大吴风草(Farfugium japonicum)为研究对象, 并以香樟萌生苗为对照, 分析各植物光合特性在不同生长光强下的动态变化。结果表明: 在不同郁闭度下, 红茴香和大吴风草具有较高的表观量子效率(AQE)、较低的光补偿点(LCP), 而香樟具有较高的最大净光合速率(P_max)和光饱和点(LSP)。随着郁闭度的增加,各植物AQE 逐渐增加, 且不同郁闭度处理间均存在显著差异(P<0.05); 香樟P_max 表现为逐渐降低的趋势, 红茴香和大吴风草则呈先上升后降低的趋势; 香樟暗呼吸速率Rd 呈现先降低后增加的趋势, 而红茴香和大吴风草则表现为逐渐降低; 各植物的LCP 和LSP 均表现为逐渐降低的趋势以适应弱光环境。可见, 香樟通过降低自身的LCP 和LSP 逐渐适应弱光环境, 但在高郁闭度下其光合作用仍然受到胁迫; 而红茴香和大吴风草则通过降低LCP、LSP 和自身能量消耗来适应弱光环境, 且在中等郁闭度下具有最高的光合能力, 充分证明其阴生特性。

Photosynthetic response to different irradiances of undergrowth plants in tree-herb plantation

Photosynthetic characteristics of Illicium henryi and Farfugium japonicum herbs were determined, with Cinnamomum camphora seedling as the control, under low, medium and high canopy densities of C. camphora forest in Songjiang, Shanghai. Results showed that I. henryi and F. japonicum had higher apparent quantum efficiency (AQE) and lower light compensation point (LCP). On the other hand, C. camphora seedling exhibited higher maximum photosynthetic rate (P_max) and light saturation point (LSP). AQE of three plant species increased with increasing canopy density, and with significant differences among different canopy densities. For I. henryi and F. japonicum, P_max initially increased and then eventually decreased, but that for C. camphora seedling decreased right throughout with increasing canopy density. While dark respiration (R_d) initially decreased and then increased for C. camphora seedling, that for undergrowth I. henryi and F. japonicum steadily decreased. There was an obvious adaptation of C. camphora seedling to low irradiance, due to decreasing LCP and LSP. But its stressed photosynthesis under high canopy density was observed. While P_max in I. henryi and F. japonicum occurred under medium canopy density, low irradiance was accommodated by not only low LCP and LSP, but also low energy consumption. This showed that I. henryi and F. japonicum were highly tolerant to shade.