脐橙幼苗新老叶片养分含量对大、中量元素短期缺乏的差异性响应

  【目的】  对比大、中量养分短期缺乏下脐橙新、老叶片中11种必需元素含量及变化，并分析缺素导致的营养元素间的相互影响。  【方法】  以一年生枳砧纽荷尔脐橙幼苗为试材进行了砂培试验。以完全营养液为对照 (CK)，设置缺氮 (?N)、缺磷 (?P)、缺钾 (?K)、缺钙 (?Ca)和缺镁 (?Mg)处理，测定不同处理脐橙叶片（老叶和新叶）生长指标及矿质元素含量。  【结果】  所有缺素处理均导致叶片叶绿素含量降低，生物量减少，以缺氮处理最为显著。缺氮降低了叶片N、Ca、Cu、Mo含量；缺磷降低了叶片P、K、Mo含量；缺钾降低了叶片K含量；缺钙降低了叶片N、Cu、Zn、Mo含量但增加了P含量；缺镁降低了叶片Ca、Mg、Zn、Mo含量但增加了K含量。以必需矿质元素为变量分别对各处理老叶和新叶进行主成分分析，老叶中第一主成分 (PC1)明显将缺钾处理与其他处理区分开，与对照相比，缺钾老叶离子组成变化为N (?3%)、P (+1%)、K (?71%)、Ca (+11%)、Mg (+39%)、B (+16%)、Mn (+11%)、Fe (+32%)、Cu (?7%)、Zn (+14%)、Mo (?63%)；新叶中PC1明显将缺氮处理与其他处理区分开，缺氮新叶离子组成变化为N (?53%)、P (+8%)、K (+7%)、Ca (?14%)、Mg (+11%)、B (+55%)、Mn (+51%)、Fe (?14%)、Cu (?57%)、Zn (+4%)、Mo (?25%)。老叶和新叶中元素含量呈正相关的元素是N-Cu、N-Ca、Mg-Mn和Cu-Mo，呈负相关的是K-Zn。  【结论】  脐橙幼苗老叶对钾的短期缺乏反应最敏感，缺钾会显著降低老叶中K和Mo含量并增加Mg和Fe含量，而新叶对氮素的短期缺乏最敏感，缺氮显著降低新叶中N、Ca、Cu和Mo含量。短期缺少P、Ca和Mg对脐橙幼苗叶片中的养分含量影响较小。

Differential response of nutrient content of new and old leaves of young navel orange to short-term deficiency of macroelements and secondary elements

  【Objectives】  We compared the changes in the essential elements of young navel orange leaves to short-term deficiency of elements.   【Methods】  Sand culture method was used for the research, with one-year-old young Newhall navel orange as test materials. The experiment included complete nutrient solution (control), N, P, K, Ca and Mg deficiency treatments. The growth and element contents of old and new leaves were measured.   【Results】  The leaf chlorophyll content and biomass decreased in all deficiency treatments. N deficiency decreased the leaf N, Ca, Cu and Mo contents, P deficiency decreased the leaf P, K and Mo contents, and K deficiency reduced the leaf K content. Ca deficiency decreased the leaf N, Cu, Zn and Mo content, but increased P content. Mg deficiency decreased the leaf Ca, Mg, Zn and Mo contents, but increased K content. Taking essential mineral elements as variables, principal component analysis was conducted on old and new leaves under each treatment, and the first principal component (PC1) of old leaves obviously distinguished K deficiency treatment from other treatments. Compared with the control, the changes of ion composition in K-deficient old leaves were N (–3%), P (+1%), K (–71%), Ca (+11%), Mg (+39%), B (+16%), Mn (+11%), Fe (+32%), Cu (–7%), Zn (+14%) and Mo (–63%). In new leaves, PC1 clearly distinguished N deficiency treatment from other treatments. The changes in ion composition of N-deficient new leaves were N (–53%), P (+8%), K (+7%), Ca (–14%), Mg (+11%), B (+55%), Mn (+51%), Fe (–14%), Cu (–57%), Zn (+4%) and Mo (–25%). N-Cu, N-Ca, Mg-Mn and Cu-Mo content between the old and new leaves were correlated positively, and the K-Zn correlated negatively.  【Conclusions】  The old leaves of young navel orange trees were sensitive to K nutrition, short-term K deficiency decreased the contents of K and Mo and increased the contents of Mg and Fe. The new leaves were sensitive to N nutrition, as short-term N deficiency decreased N, Ca, Cu and Mo contents. Both the new and old leaves were not sensitive to P, Ca and Mg deficiencies in short period.