印楝种源不同生长季节冠层间的光响应特征

Light Response Characteristics of Azadirachta indica Provenances in Different Growing Seasons Within Crowns

应用Li-6400P便携式光合作用测定仪,研究了印楝4个种源在不同生长季节、不同冠层间的光响应特征。结果表明:印楝种源间光响应曲线因叶龄和冠层部位的不同而呈现不同的特征格局;在不同生长季节,印楝各种源的光补偿点和饱和点差异较大。生长初期的光补偿点相对较高,到生长盛期呈下降状态,总体上生长初期>生长末期>生长盛期。印楝光饱和点的季节变化表现为:从生长初期到生长盛期均呈现逐渐上升趋势,但到生长末期逐渐下降。从不同冠层叶片的饱和点与补偿点来看,各种源排序均为冠上层>冠中层>冠下层,这种排序关系体现了种源间叶片对不同光照条件的生态适应性;在各生长季节中,通过光响应测定所获得的印楝种源(KA种源)最大净光合速率可达18.95μmol·m-2.s-1,其余3个种源的最大净光合速率为13.98 16.35μmol·m-2.s-1。根据印楝具有较高的光饱和点及光补偿点,以及对高光强具有较强的适应性和较大的光合能力等光合特征,综合推断本文所研究的4个印楝种源均体现出典型的喜光阳性特征。

Light responses for net photosynthetic rate of four Azadirachta indica provenances in different growing seasons within crowns were measured with Li-6400 Portable Photosynthesis（Li-Cor Inc.,USA）.The results showed that light response curves of the four provenances exhibited different characteristics with different aged leaves and positions within the tree crowns.There were obvious differences in the light saturation point（LSP） and light compensation point（LCP） among the four A.indica provenances in different growing seasons.For the same provenance,the LCP of initiation phase was the highest and that of prosperous phase was the lowest.For the seasonal variation of the LSP,there was a trend of initially increasing from initiation phase to prosperous phase,then decreasing in the last phase.Rankings of LCP and LSP in the different layers in the tree crowns were similar,i.e.,the upper crown mid crown lower crown,which expressed the ecological adaptability to the variant light conditions.Among the four provenances,the maximum net photosynthetic rate of A.indica originating from Kalyani（KA） through the light response measurements was the highest（about 18.95 μmol·m^-2·s^-1）,and that of other three provenances was between 13.98-16.35 μmol·m^-2·s^-1.According to those photosynthetic characteristics,i.e.the higher LCP and LSP,the stronger adaptability to high light intensity and the higher photosynthetic capacity,the four provenances of A.indica all showed typical heliophyte properties.