Nitrogen management and senescence in two maize hybrids differing in the persistence of leaf greenness: agronomic, physiological and molecular aspects

Abstract

• Here, nitrogen management within the plant was compared in an early‐senescing maize hybrid and in a late‐senescing maize hybrid, both grown under field conditions with a high fertilisation input involving large quantities of fertiliser. • We monitored, in representative leaf stages, the changes in metabolite content, enzyme activities and steady‐state levels of transcripts for marker genes of N primary assimilation, N recycling and leaf senescence. • The hybrids differed in terms of persistence of leaf greenness, the expression of marker genes and the concentration of enzymes used to describe the transition from N assimilation to N recycling. The transcription of leaf‐senescence marker genes did not differ. Agronomic studies confirmed the ability of the late‐senescing hybrid to absorb and store more N in shoots. • Despite the differences in the mode of N management adopted by the two hybrids, we conclude that leaf senescence occurs independently of the source‐to‐sink transition at the high level of fertilisation used involving large quantities of fertiliser. The possibility of improving N metabolic efficiency in the latest maize hybrids is discussed.