The present invention discloses transgenic plants having an altered level
of NAP protein compared to that of a non-transgenic plant, where the
transgenic plants display an altered leaf senescence phenotype relative
to a non-transgenic plant, as well as mutant plants comprising an
inactivated NAP gene, where mutant plants display a delayed leaf
senescence phenotype compared to that of a non-mutant plant. The present
invention also discloses methods for delaying leaf senescence in a plant,
as well as methods of making a mutant plant having a decreased level of
NAP protein compared to that of a non-mutant plant, where the mutant
plant displays a delayed leaf senescence phenotype relative to a
non-mutant plant. Methods for causing precocious leaf senescence or
promoting leaf senescence in a plant are also disclosed. Also disclosed
are methods of identifying a candidate plant suitable for breeding that
displays a delayed leaf senescence and/or enhanced yield phenotype.