不同土壤水分条件下107杨幼苗(Populus×euramericanacv.“74/76”)秋季光响应研究

Photoresponse of Populus×euramericana cv."74/76" Cutting Seedlings in Different Soil Moisture Conditions in Autumn

在北京地区，利用Li-6400便携式光合仪的Li-6400-02B红蓝光源设定从O～2000μmol·m^-2·s^-1的光强，通过人工控水的方法取得3个不同的水分梯度，对秋季107杨（Populus×euramericana cv．“74／76”）1a生扦插苗木的各生理生长参数的光响应规律进行研究。结果表明，土壤含水量分别为13．249，6～17．65％、17．65％～22．06％时，107杨1a生扦插苗净光合速率能维持较高水平，当土壤含水量低于13．24％时，其净光合速率受气孔限制作用明显降低，苗木生长受到影响。

Physiological indices of 1-year-old cutting seedlings of Populus × euramericana cv. ＂74/76＂ was conducted in this study in auturm in Beijing were measured to study the photoresponse of the seedlings under 3 artificially controlled water levels corresponding to 40 % - 100 % of the water holding capacity（WHC） of the soil and with the simulated photosynthetic radiation （SPR） of portable photosynthesis system（Li- 6400）. The results showed that photosynthetic rate（Pn）, transpiration rate （Tr） and water use efficiency of leaf （WUE） had clear threshold value response to soil moisture and photosynthetic active radiation. To maintain the normal growth and higher levels Pn, soil water content should be within the range of 17.65%-22.06%, and 13.24%-17.65% . When the soil water content is below 13.24%, the decline of Pn was mainly caused by stomatal limitation.