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采用红外线CO_2分析法研究了I-69杨和毛白杨光合速率与光强、CO_2浓度、叶龄等的关系;用改良干重法研究了I-69杨光合速率的日进程和年进程;研究了叶绿素含量、比叶重、单片叶面积变化的年进程。结果表明,I-69杨的光饱和点与毛白杨相近,光补偿点高于毛白杨,CO_2补偿点比毛白杨低。I-69杨的净光合速率高,功能叶数量多,功能期长,这些是I-69杨比毛白杨速生的基础。I-69杨在高温、湿润的季节(7、8月)光合日进程仍表现为双峰曲线,说明它对水分亏缺很敏感。I-69杨的光合年进程也表现为双峰曲线,峰期分别出现在6、7月和10月。8月光合速率降低是和单片叶面积增大、叶绿素含量降低和比叶重下降有关的。此外,在速生时期矿质和氮素营养缺乏可能是光合速率降低的外部原因。
The relationship between photosynthetic rate and light intensity, CO2 concentration and leaf age of I-69 and Populus tomentosa was studied by infrared CO_2 analysis method. The daily and diurnal course of photosynthetic rate of I-69 were studied by modified dry weight method. The chlorophyll content, specific leaf weight, single leaf area changes in the course of the year. The results showed that the light saturation point of I-69 was similar to that of Populus tomentosa and the light compensation point was higher than that of Populus tomentosa. The CO 2 compensation point was lower than Populus tomentosa. I-69 Yang net photosynthetic rate, the number of functional leaves, long functional period, these are I-69 poplar poplar fast-growing basis. The photosynthetic diurnal course of I-69 at high temperature and wet season (July and August) still showed a bimodal curve, indicating that it is sensitive to water deficit. The photosynthetic annual process of I-69 also showed a bimodal curve, with peak periods occurring in June, July and October respectively. The decrease of photosynthetic rate in August was related to the increase of single leaf area, the decrease of chlorophyll content and the decrease of leaf weight. In addition, mineral and nitrogen deficiencies in fast-growing period may be the external cause of the decrease in photosynthetic rate.