Adaptive strategies of old and young leaves to alkali-stress in hexaploid wheat

Alkali stress is an important limiting factor for agricultural production. The aim of this study was to investigate whether old and young leaves have different biochemical responses to alkali stress in hexaploid wheat, and to provide molecular dissection of these differential responses on the basis of proteomic profiling. Under alkali stress, hexaploid wheat accumulated higher concentrations of Na+ in older leaves to protect young leaves. Young leaves accumulated amino acids, carbohydrates, and dehydrin proteins to relieve Na+ toxicity. Under alkali stress, 14-3-3 protein abundance was enhanced in old leaves to accelerate Na+ compartmentation in the vacuole. Abundances of 27 ribosomal proteins were significantly decreased in old leaves but not in young leaves, and many proteinases and ribonucleases also were significantly upregulated by alkali stress in old leaves.