The present invention provides new methods of delaying senescence in a plant by inhibiting ACC oxidase, or EIN2 activity the plant. In particular, it is directed to producing green leaves in maize through inhibition of ethylene. The genes involved in producing this phenotype include ACC deaminase, ethylene response sensor ("ERS"), ethylene resistan ("ETR"), and ethylene insensitive ("EIN"). The delay in senescence can be achieved through the production of ACC deaminase, mutated ETR1 and ERS2 proteins, as well as overexpression of wild-type ETR1 and ERS2 proteins.