珙桐一年生苗光合特性的研究

Photosynthetic characteristics in leaves of Davidia involucrate seedlings

采用美国LI-COR公司生产的LI-6400便携式光合作用测定仪的开放系统对一年生珙桐的光合生理特性进行了研究。结果表明:①在夏季晴朗的天气中,一年生珙桐苗期的光合速率日变化为双峰曲线,有明显的"午休"现象,光合"午休"是由于气孔因素造成。②一年生珙桐苗期光补偿点和光饱和点分别为57.27μmol.m-2.s-1和625.07μmol.m-2.s-1,说明珙桐是阳生植物但对光的适应范围窄。③一年生珙桐苗期叶片光能利用率较低,约为0.070 5 mmol CO2/mol photons。④逐步回归分析表明:光合有效辐射、蒸腾速率、气孔导度和胞间CO2浓度对一年生珙桐苗期叶片光合速率影响较大。

Photosynthetic characteristics of 1-year Davidia involucrate seedlings were measured with the Licor-6400 portable photosynthetic system. The results showed that the variation of diurnal net photosynthetic rate （Pn） was a double-peak curve at sunny days in summer, indicating there was a significant ＂noon break＂ phenomenon caused by stomas. The light compensation points topped at 57.27μmol.m2.s-1 and the light saturation point was 625.07μmol.m2.s-1, which indicated that Davidia involucrate was a sun-favor plant, but its range of light adaptation was narrow. The solar energy utilization efficiency of seedlings was low, about 0.070 5 mmol CO2/mol photons. Using the stepwise multiple regression we found that PAR, Tr, Gs and Ci were the most dominant factors affecting the photosynthetic rate of 1-year Davidia involucrate seedlings.