Nitrogen management and senescence in two maize hybrids differing in the persistence of leaf greenness: agronomic, physiological and molecular aspects.
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.
Unité de Nutrition Azotée des plantes, INRA, R.D. 10, 78026 Versailles Cedex, France.
Antoine
A
Martin
Xana
X
Belastegui-Macadam
Isabelle
I
Quilleré
Mathieu
M
Floriot
Marie-Hèlène
MH
Valadier
Bernard
B
Pommel
Bruno
B
Andrieu
Iain
I
Donnison
Bertrand
B
Hirel
D000383:Agriculture; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006824:Hybridization, Genetic; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*
D010940:Plant Proteins; D018749:RNA, Plant; D009584:Nitrogen