不同秋眠级紫花苜蓿茎和叶的碳、氮、磷化学计量特征

Stoichiometric Characteristics of Carbon,Nitrogen and Phosphorus in Stems and Leaves of Alfalfa with Different Fall Dormancy Levels

为明确不同秋眠级紫花苜蓿品种间营养元素限制性和分配格局的差异性,以国内外收集的10个不同秋眠级紫花苜蓿品种为研究对象,分析其叶片和茎秆的碳(C)、氮(N)、磷(P)含量和化学计量比变化特征。结果表明,紫花苜蓿叶片和茎秆中N和P含量均随着秋眠级的升高呈先降低后升高的趋势,C含量以及C∶N、C∶P和N∶P呈相反的趋势。不同秋眠级苜蓿品种叶片中各元素含量为:秋眠级为4级的新疆大叶苜蓿叶片C含量、秋眠级为9级的WL656HQ叶片N含量均显著大于其他各秋眠级苜蓿品种(P<0.05)。苜蓿茎秆C含量在各秋眠级苜蓿品种间均差异不显著,N、P含量变化与苜蓿叶片相同,且第2茬叶片和茎秆C、N和P含量的变异系数均低于第1茬,两茬表现出相同的规律。除第2茬苜蓿的叶片外,秋眠级对苜蓿叶片和茎秆P含量的影响最大,其次为N含量,对C含量的影响最小。不同茬次间,秋眠级对苜蓿叶片C∶P的影响最大,对N∶P的影响最小。苜蓿叶片C含量与叶片和茎秆C∶N、C∶P呈显著正相关(P<0.05),而与叶片和茎秆N含量呈显著负相关(P<0.05);叶片N、P含量分别与茎秆N、P含量呈显著正相关(P<0.05)。叶片C∶N、C∶P分别与茎秆C∶N、C∶P呈显著正相关(P<0.05),与茎秆N含量呈显著负相关(P<0.05);茎秆C含量与茎秆C∶N呈显著正相关(P<0.05),茎秆N含量与茎秆C∶N呈显著负相关(P<0.05);茎秆C∶P与茎秆N∶P呈显著正相关(P<0.05)。非秋眠型和秋眠型苜蓿的生长受N元素限制,中等秋眠型苜蓿的生长受N和P元素共同影响,在不同秋眠级苜蓿生产过程中,应重点考虑N、P的供需平衡。

This study determined the contents of carbon(C),nitrogen(N),and phosphorus(P)and their stoichiometric characteristics in stems and leaves of 10 varieties to clarify the differences in nutrient limitation and distribution patterns of alfalfa with different fall dormancy levels.The results showed that alfalfa leaves and stems’N and P contents tended to decrease and then increase with the increasing fall dormancy level,while the C content and C∶N,C∶P and N∶P ratios exhibited the opposite trend.The leaf C content of‘Xinjiang Daye’with fall dormancy level 4 and the leaf N content of‘WL656HQ’with fall dormancy level 9 were significantly higher than those of other alfalfa varieties(P<0.05).The variation of C content in stems was not significant among alfalfa varieties with different fall dormancy levels.The stem N and P contents variation was the same as the alfalfa leaf.The coefficients of leaf and stem C,N,and P contents variation of the second cut were lower than that of the first cut,and both cuts showed the same pattern.Except for the leaves of the second cut of alfalfa,the fall dormancy level had the most significant effect on the P content of alfalfa leaves and stems,followed by the N content and C content.Between the two cuts,the fall dormancy level had the most significant effect on leaf C∶P ratio and the lowest effect on N∶P ratio.The leaf C content of alfalfa was positively correlated with C∶N and C∶P ratios of leaf and stem,while it was negatively correlated with N content of leaf and stem(P<0.05).The leaf N and P contents were positively correlated with stem N and P contents(P<0.05).The leaf C∶N and C∶P ratios were positively correlated with stem C∶N and C∶P ratios(P<0.05),while negatively correlated with stem N content(P<0.05).The stem C content and N content had significantly positive and negative correlations with the stem C∶N ratio(P<0.05).The stem C∶P ratio was positively correlated with the stem N∶P ratio(P<0.05).In conclusion,the growth of non-fall-dormant and fall-dormant alfalfa was affected by N.The growth of medium fall-dormant alfalfa was affected by both N and P.During the growth of alfalfa with different fall dormancy levels,it is important to consider the balance of N and P supplying and demanding.