水分对不同生育时期紫花苜蓿茎叶碳、氮、磷含量及化学计量特征的影响

Effect of Water Addition on Carbon,Nitrogen and Phosphorus Concentrations,and Stoichiometric Characteristics of Alfalfa Stems and Leaves at Different Growth Stage

通过设置35%(Low water,LW)、50%(Medium water,MW)和80%(High water,HW)的最大田间持水量(Maximum field water capacity,FWC)3个水分处理,探索紫花苜蓿不同生育时期地上营养器官碳、氮、磷含量及其化学计量比对水分添加的响应规律。研究表明:1)碳受水分和生育时期的影响较小;分枝期和现蕾期茎中氮含量随水分增加递减,现蕾期和初花期叶中氮、磷含量随水分增加递增,分枝期和初花期茎中磷含量随水分增加递增,而现蕾期相反。2)随紫花苜蓿生长,茎中碳含量逐渐增加,叶中氮和磷含量逐渐降低,茎叶中氮、磷含量可影响碳氮比、碳磷比及氮磷比。综上所述,不同生育期紫花苜蓿叶片对干旱胁迫响应更加敏感,而茎叶中磷含量可影响紫花苜蓿生长,适量添加水分能够缓解贫瘠土壤中紫花苜蓿茎叶磷含量受限情况。

Three water addition treatments including 35%(Low water,LW),50%(Medium water,MW)and 80%(High water,HW)of maximum field water capacity(FWC)were set to explore the response of carbon,nitrogen,phosphorus concentrations and their stoichiometric ratios of aboveground vegetative organs to water addition at different growth stages of alfalfa.The results showed as following aspects.Firstly,carbon concentration was less affected by water addition and growth period.The nitrogen concentration in stems decreased with the increase of water addition at branching and budding stages.The nitrogen and phosphorus concentrations in leaves increased with the increase of water addition at budding and early flowering stages.The phosphorus concentration in stems increased with the increase of water addition at branching and early flowering stages,but the changes of phosphorus concentration in stems was opposite at budding stage.Secondly,with the growth of alfalfa,the carbon concentration in stems gradually increased,and the nitrogen and phosphorus concentrations in leaves gradually decreased.The concentrations of nitrogen and phosphorus in stems and leaves could affect the ratio of carbon to nitrogen,carbon to phosphorus and nitrogen to phosphorus.In conclusion,alfalfa leaves at different growth stages were more sensitive to drought stress,and the phosphorus concentrations in stems and leaves could affect the growth of alfalfa.Appropriate water addition can alleviate the limitation of phosphorus concentrations in stems and leaves of alfalfa in nutrient-poor soils.