不同种源香椿苗木光合特性比较

以江苏南京、四川广元、湖南洞口、湖北随州、河南西峡、陕西安康等6个种源的香椿1 a生实生苗为材料进行盆栽试验,研究光合的季节性动态变化、光合日变化规律及其与环境影响因子的关系.结果表明:不同种源香椿苗木净光合速率季节变化趋势基本一致,5月下旬至6月下旬光合较弱,缓慢增加,7月下旬达到最高峰,8月下旬出现低谷,9月下旬各种源光合速率又大幅增加,出现次高峰.单叶Pn日变化为不对称的双峰曲线,江苏南京和湖北随州种源最高峰出现在8:00,其他4个种源皆出现在上午10:00,次高峰皆出现在14:00,"午休"现象明显,受气孔因素和非气孔因素的双重调节.光合特征参数Pn、Tr、Gs、Ci和WUE的种源间差异达极显著水平(P<0.01),说明不同种源香椿苗木的光合能力及水分利用能力差别较大.

Comparison of Photosynthesis in Seedlings of Different Toona Sinensis Provenances

The seasonal and daily changes of photosynthesis and its relation with the factors of surroundings were studied in potted one-year-old seedlings of six Toona sinensis provenances from Nanjing of Jiangsu,Guangyuan of Sichuan,Dongkou of Hunan,Suizhou of Hubei,Xixia of Henan and Ankang of Shanxi.The results showed that the seasonal changes of the net photosynthetic rate(Pn) were similar for six provenances.In May and June they were low and increased gradually,and reached to peak in July,but then sharply decreased to very low in August.In September the Pn increased greatly and reached to its secondary peak.The daily changes of Pn were unsymmetrical two-peak curves.The first peaks appeared at eight o'clock in Suizhou and Nanjing provenances,and the others were at ten o'clock.The secondary peaks were all appeared at two o'clock in the afternoon.This indicated an obvious the mid-day depression of photosynthesis regulated by stomatic and non-stomatic factors doubly.There were significant differences(P< 0.001)in photosynthetic parameters of Pn,transpiration rate(Tr),stomatic conductance(Gs),intercellular CO2 concentration(Ci) and water use efficiency(WUE) among six provenances.Correlation analysis showed that Pn was significantly positive correlation to Tr and WUE(P< 0.05),and extremely significant positive correlation to Gs(P< 0.01).However there was no significant correlation between Pn and Ci(P< 0.01).