夜间低温胁迫对两种生长光强下藤黄幼苗叶片荧光特征和活性氧代谢的影响

对两种不同生长光强下（自然光的8％和50％）西双版纳热带雨林木本植物藤黄（Garcinia han-buryi）幼苗经夜间低温（4℃）处理后荧光特性和活性氧代谢的研究结果表明，低温使藤黄叶片光合机构PSⅡ原初光能转化效率（Fv/Fm）、PSⅡ非环式电子传递的量子效率（ФPSⅡ）、非光化学猝灭系数（NPQ）下降，原初荧光（F0）上升。低温胁迫消除后，生长在50％光强下藤黄叶片的Fv/Fm和F0在3d后仍不能完全恢复，而生长在8％光强下藤黄叶片的Fv/Fm和F0基本恢复，说明低温使生长在8％光强下藤黄的光合机构PSⅡ反应中心受到可逆失活，而生长在50％光强下藤黄的光合机构受到氧化伤害。随着低温胁迫时间的延长，两种生长光强藤黄叶片活性氧保护酶（SOD，CAT，APX）的活性虽升高，但O2^-的生成速率、H2O2和MDA含量积累增加。而在恢复阶段，生长在8％光强比生长在50％光强下藤黄叶片的活性氧含量下降得快，进一步说明生长在高光强的植物比生长在低光强的植物受低温伤害大。

Effect of low nocturnal temperature stress on fluorescence characteristics and active oxygen metabolism in leaves of Garcinia hanburyi seedlings grown under two levels of irradiance

The fluorescence characteristics and active oxygen metabolism in leaves in Garcinia hanburyi seedlings grown under two irradiance levels (50% and 8% of full natural sunlight) and nocturnal low temperature (4 degrees C) were studied in Xishuangbanna. The results showed that the photochemical efficiency of PS II (Fv/Fm), the quantum yield of PS II linear electron transport (phi PS II) and non-photochemical quenching (NPQ) were decreased, but the initial fluorescence yield (F0) were increased with prolonged stress time of low temperature in leaves of Garcinia hanburyi grown under the two different irradiance levels. After three days of recovery treatment, the Fv/Fm and F0 of Garcinia hanburyi grown under 50% natural irradiance were not recovered completely, while those of the seedlings grown in 8% natural irradiance were recovered almost completely, which indicated that the photosynthetic apparatus of Garcinia hanburyi grown under 50% irradiance was injured by photooxidation, but that of seedlings grown in 8% irradiance was only reversibly inactivated by the nocturnal low temperature stress. In the mean time, although the activities of protective enzymes (SOD, CAT, and APX) increased, the O2-. production rate and H2O2 content also increased with the duration of the stress. The MDA also accumulated in leaves of Garcinia hanburyi grown under two different irradiance levels. After three day's recovery, much less active oxygen was produced in leaves of Garcinia hanburyi grown under 8% than that under 50% irradiance. The implication of the results for practice were also discussed.