旱季降雨格局变化对益智生长和碳氮代谢的影响

益智是我国四大南药之一，其间作在橡胶林下成为胶园最重要的农林复合模式。项目组前期研究发现，旱季降雨不足是橡胶林下益智生长和光合的主要限制因子。然而，目前对益智如何应对旱季降雨格局变化的认识非常有限。为研究旱季降雨格局变化对益智生长和碳氮代谢的影响，在实验中模拟3个降雨量梯度：减雨量（W-）10 mm/月、自然雨量（W）25 mm/月、增雨量（W+）40 mm/月，并设置5 d和10 d的降雨间隔期，通过双因素实验分析益智植株的生长参数、碳水化合物和氮化合物水平以及与碳和氮代谢相关的关键酶活性。结果表明：（1）益智的地上生物量和地下生物量随着降雨量的减少而下降。在所有降水水平下，5 d处理下的生物量均显著高于10 d（P<0.05），降雨量减少和降雨间隔期延长均抑制植株生物量的增加。在W-处理下，10 d的叶片含水率比5 d显著增加3.63%；（2）降雨减少改变了碳代谢酶的活性，抑制了AMY和INV活性，促进了SPS活性，但这种促进作用随着降雨间隔期延长变得不显著。降雨量减少促进了非结构碳水化合物（可溶性糖和淀粉）积累；（3）降雨减少降低了益智叶片全N含量，5 d处理组中W+和W-的全氮含量比10 d显著增加8.33%和9.81%，降雨量变化改变了N代谢组分；（4）同时GS/GOGAT循环活性以及NR和NiR酶活性增加，这加速了硝态氮还原和铵态氮同化。在W处理下，5 d处理组中的硝态氮和铵态氮比10 d显著降低了57.54%和152.98%。因此，在旱季降雨格局变化会影响益智的生物量、碳氮化合物及代谢酶变化，但益智通过生物量分配和叶片C、N代谢调节来适应不同的干旱胁迫，以保证益智植株的正常生长。

Effects of Precipitation Pattern Change on the Growth Carbon and Nitrogen Metabolism of Alpinia oxyphylla During Dry Season

Alpinia oxyphylla is one of the four southern medicines in China, and its cultivation under rubber forest has become the most important agroforestry mode in rubber plantation. The study previously found that insufficient precipitation is the main limiting factor for the growth and photosynthesis of A. oxyphylla during the dry season. However, our knowledge is still limited in understanding the response of A. oxyphylla to precipitation pattern change during the dry season. Three precipitation gradients including decreased precipitation (W-)10 mm/ month, natural precipitation (W) 25 mm/ month and increased precipitation (W+) 40 mm/ month, and set 5 days (5 d) and 10 days (10 d) of interval between precipitation were simulated in the study. The leaf water content in W- plant of 10 d was significantly increased by 3.63% compared with 5 d. In addition, we analyzed plant growth parameters, carbohydrate and N compound levels and the activity of key enzymes related to C and N metabolism through two factors experiment of precipitation and precipitation interval. The aboveground biomass and underground biomass of A. oxyphylla decreased with the decrease of precipitation. The total biomass of 5 d was significantly higher than that of 10 d at all precipitation levels (P<0.05). The plant growth was further inhibited by precipitation and extended precipitation interval. The decreased precipitation changed the activity of carbon metabolism enzymes, inhibited the AMY and INV activity, and promoted the SPS activity. However, this promoting effect became trivial with extended precipitation interval. The accumulation of non-structural carbohydrates (soluble sugar and starch) was promoted by decreased precipitation and activity change of C metabolic enzymes. The decreased precipitation lowered the total N content of A. oxyphylla leaves, and the total N content of W+ and W- in 5 d was significantly increased by 8.33% and 9.81% compared with that of 10 d. The N metabolic components changed in plant leaves with decreased precipitation. Meanwhile, the GS/GOGAT, NR and NiR activity increased with the decreased precipitation, which accelerated nitrate nitrogen (NO₃^-) reduction and ammonium (NH₄⁺) assimilation. The NO₃^- and NH₄⁺ in W plant in 5 d were significantly decreased by 57.54% and 152.98 compared with that of 10 d. Therefore, the change of precipitation pattern could affect the change of biomass carbon and nitrogen compounds and metabolic enzymes of the plant during the dry season. In summary, drought stress was adapted to ensure normal growth of A. oxyphylla through biomass allocation and C and N metabolism regulation.