The response of photosynthetic characteristics to density of Cenchrus spinifex at different phenological periods
[Objective]This study aims to explore the adaptive characteristics of photosynthesis in Cenchrus spi-nifex In response to varying densities at different phenological periods,providing a theoretical basis for the develop-ment of effective prevention and control technologies.[Method]In situ field experiments with 5 sowing times(May 28 th,June 13 th,June 28 th,July 16 th,and July 29 th)and five density levels(5,7,9,18,and 21 plants/m2).The net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),and intercellular carbon dioxide con-centration(Ci)of C.spinifex were measured using a spatial time substitution method.Differences in photosynthetic characteristics of C.spinifex under varying densities and phenological periods were analyzed,and regression analysis was employed to model the relationship between Pn and Gs in relation to density.[Result]1)Phenological stage and density significantly affected Pn,Gs,Tr,and Ci of C.spinifex(P<0.05).Except for Gs,the interaction between pheno-logical stage and density was not significant for other photosynthetic parameters.2)During the heading stage,the Pn,Gs,and Tr were significantly higher than in other stages(P<0.05),while Ci was significantly lower(P<0.05).3)At a medium density of 9 plants/m2,Pn,Gs,and Tr were significantly elevated compared to other densities(P<0.05),while Ci was significantly lower(P<0.05).4)The fitting parameter a of Pn-Gs relationship exhibited an ini-tial increase followed by a decrease with increasing density,reaching a maximum value of 19.45 at a density of 13.65 plants/m2.[Conclusion]The photosynthetic characteristics of C.spinifex at different phenological stages had certain internal regulatory mechanisms.The species adjusts to changes in density changes through stomatal closure and varia-tions in photosynthetic intensity.Increased density intensifies the the impact of stomatal limitations on the net photo-synthetic rate,but a critical density exists;exceeding this critical value,non-stomatal factors had a greater impact on net photosynthetic rate.
万方数据
维普
