羊草和紫花苜蓿人工草地光合特性

Photosynthetic characteristics of Leymus chinensis and Medicago sativa in artificial grassland

为探究单播与混播人工草地对羊草和紫花苜蓿光合特性的影响,测定2种牧草光合特性日变化进程,比较不同处理下羊草和紫花苜蓿光合特征。结果表明:单播处理下,羊草和紫花苜蓿的净光合速率、蒸腾速率、叶片温度呈单峰型,紫花苜蓿的气孔导度呈单峰型,羊草的气孔导度和水分利用效率呈双峰型。混播处理下,羊草和紫花苜蓿的净光合速率、蒸腾速率、叶片温度日变化呈单峰型,羊草的气孔导度和水分利用效率呈单峰型,紫花苜蓿的气孔导度呈双峰型。混播处理下,羊草净光合速率峰值显著高于单播,分别为17.72和13.65μmol CO_(2)·m^(-2)·s^(-1)。单播和混播处理下,羊草叶绿素含量均高于紫花苜蓿,羊草叶片氮含量均低于紫花苜蓿,且混播羊草叶片氮含量显著高于单播羊草,二者分别为27.60和22.55 g·kg^(-1)。不同种植方式下,羊草和紫花苜蓿的净光合速率与气孔导度、蒸腾速率呈显著正相关,与胞间CO_(2)浓度呈显著负相关,紫花苜蓿的净光合速率与叶片温度、水分利用效率呈显著正相关。混播处理有利于增加羊草叶片氮含量。试验结果为牧草光合特性对人工草地种植方式的响应提供理论基础。

To explore the effect of monoculture and mixture sowing artificial grassland on the photosynthetic characteristics of Leymus chinensis and Medicago sativa,we determined the diurnal variation of photosynthetic properties of L.chinensis and M.sativa under different treatments.The results showed that the diurnal changes of net photosynthetic rate,blade temperature and transpiration rate of L.chinensis and M.sativa showed‘unimodal type’in monoculture,the stomatal conductance of M.sativa showed‘unimodal type’,and the stomatal conductance and water use efficiency of L.chinensis showed‘bimodal type’.Under the mixed sowing treatment,the diurnal changes of net photosynthetic rate,blade temperature and transpiration rate of L.chinensis and M.sativa showed‘unimodal type’,the stomatal conductance and water use efficiency of L.chinensis showed‘unimodal type’,and the stomatal conductance of M.sativa showed‘bimodal type’.The peak photosynthetic rate of L.chinensis under mixture was signi-ficantly higher than that under monoculture,being 17.72 and 13.65μmol CO_(2)·m^(-2)·s^(-1),respectively.Under monoculture and mixture sowing treatments,the chlorophyll content of L.chinensis was higher than that of M.sativa,nitrogen content of the leaves of L.chinensis was lower than that of M.sativa,and the nitrogen content in the leaves of mixture sowing L.chinensis was significantly higher than that of monoculture sowing L.chinensis,which were 27.60 and 22.55 g·kg^(-1),respectively.Net photosynthetic rates of L.chinensis and M.sativa were significantly positively correlated with stomatal conductance and transpiration rate,and significantly negatively correlated with intercellular CO_(2)concentration under different planting methods.Net photosynthetic rate of M.sativa was significantly positively correlated with blade temperature and water use efficiency.In summary,mixed sowing was beneficial to enhance nitrogen content of L.chinensis.Our results provided a theoretical basis for the response of the photosynthetic characteristics of forage to planting mode of artificial grassland.