不同物候期少花蒺藜草光合特征对密度的响应

The response of photosynthetic characteristics todensity of Cenchrus spinifex at different phenologicalperiods

摘要:

【目的】 探究不同物候期少花蒺藜草（Cenchrus spinifex）光合特征对密度的适应特性，也为防控技术的科学制定提供理论依据。【方法】 通过野外原位试验，设置5 个播种时间（5 月28 日、6 月13 日、6 月28 日、7 月16 日和7 月29 日）和5 个密度（5、7、9、18 和21 株/m2）水平，以空间代时间测量少花蒺藜草净光合速率（Pn），气孔导度（Gs），蒸腾速率（Tr）和胞间二氧化碳浓度（Ci），分析不同密度和物候期下少花蒺藜草光合特征的差异，采用回归分析拟合Pn-Gs方程参数与密度关系。【结果】 1）物候期和密度对少花蒺藜草Pn、Gs、Tr 和Ci 均有显著影响（P＜0. 05），除Gs 外，物候期和密度对其他光合性能参数的交互影响不显著；2）抽穗期少花蒺藜草Pn、Gs、Tr显著高于其他时期（P＜0. 05），而Ci显著低于其他时期（P＜0. 05）；3）中等密度（9 株/m2）下Pn、Gs、Tr显著高于其他密度（P＜0. 05），Ci显著低于其他密度（P＜0. 05）；4）少花蒺藜草Pn-Gs的拟合方程参数a 随密度升高呈现先升高后降低变化，密度为13. 65 株/m2时，参数a 有最大值，为19. 45。【结论】 不同物候期少花蒺藜草光合特征具有一定内在调节机制，少花蒺藜草通过调整气孔闭合，改变光合强度响应密度变化，密度越高净光合速率受气孔限制影响越大，但存在临界值，超过临界值后非气孔因素对净光合速率的影响更大。

Abstract:

【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 developmentof effective prevention and control technologies.【Method】 In situ field experiments with 5 sowing times （May28 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）. Thenet photosynthetic rate（ Pn），stomatal conductance（ Gs），transpiration rate（ Tr），and intercellular carbon dioxide concentration（Ci ） of C. spinifex were measured using a spatial time substitution method. Differences in photosyntheticcharacteristics of C. spinifex under varying densities and phenological periods were analyzed，and regression analysiswas employed to model the relationship between Pn and Gs in relation to density.【Result】1） Phenological stage anddensity significantly affected Pn，Gs，Tr，and Ci of C. spinifex（P＜0. 05）. Except for Gs，the interaction between phenologicalstage 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 initialincrease followed by a decrease with increasing density，reaching a maximum value of 19. 45 at a density of 13. 65plants/m2.【Conclusion】The photosynthetic characteristics of C. spinifex at different phenological stages had certaininternal regulatory mechanisms. The species adjusts to changes in density changes through stomatal closure and variationsin photosynthetic intensity. Increased density intensifies the the impact of stomatal limitations on the net photosyntheticrate，but a critical density exists；exceeding this critical value，non-stomatal factors had a greater impact onnet photosynthetic rate.