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.