黄土丘陵区白羊草与达乌里胡枝子混播的光合生理日变化研究

Photosynthetic Diurnal Changes of Bothriochloa ischaemum Mixed Sowing with Lespedeza davurica in Loess Hilly-gully Region

采用生态替代法,按照白羊草(Bothriochloa ischaemum,B)和达乌里胡枝子(Lespedeza davurica,D)行比设置了7种混播比例组合(即0∶10,2∶8,4∶6,5∶5,6∶4,8∶2和10∶0),比较研究了白羊草在不同混播比例组合下的光合生理日变化特征。结果表明:不同混播比例组合下,白羊草光合速率日变化均呈双峰曲线,具有明显的光合"午休"现象,峰值分别出现在10:00和16:00左右,峰谷出现在12:00左右;除B4D6比例下白羊草蒸腾速率日变化呈双峰曲线外,其他比例下均呈单峰曲线;各混播比例组合下白羊草叶片水分利用效率日变化均呈双峰曲线,峰值和峰谷出现时间与光合速率一致。相比其他组合比例,白羊草在B8D2和B6D4比例下均具有较高的Pn日均值,较低的Tr日均值和较高的WUEL日均值,说明这2种组合比例有利于改善其光合作用,提高其叶片水分利用效率。

Field experiments were conducted using a replacement series design in which Bothriochloa ischaemum（B） and Lespedeza davurica（D） were sowed at row ratios of 0∶10,2∶8,4∶6,5∶5,6∶4,8∶2 and 10∶0 in the same plot.The photosynthetic diurnal change characteristics of B.ischaemum in different mixed sowing ratios were investigated and compared.Results indicated that the diurnal changes of net photosynthetic rate of B.ischaemum presented a double-peak pattern cure under different mixed sowing ratios,showing obvious photosynthesis midday depression phenomenon.Peak values appeared at 10：00 and 16：00,respectively,while the lowest value appeared at 12：00.Except at B4D6 ratio,in which the transpiration rate diurnal changes of B.ischaemum presented a double-peak pattern cure,the curves had only one peak at the other mixed sowing ratios.Diurnal change of leaf instantaneous water use efficiency presented a double-peak pattern cure at all mixed sowing ratios,and the peak and lowest values appeared at the same time as photosynthetic rate.Compared with other ratios,B.ischaemum had higher daily average photosynthetic rate,higher daily average leaf water use efficiency and lower daily average transpiration rate at B8D2 and B6D4 ratios,which indicated that these two mixed sowing rations are beneficial to improve the photosynthesis and leaf water use efficiency of B.ischaemum.