ABSTRACT
Leaf senescence is a naturally-occurring process during the life cycle of plants but can be induced or accelerated prematurely by environmental stresses. At the onset of leaf senescence, macromolecules, including chlorophyll, proteins, lipids, and DNA, are degraded, which can lead to leaf death and a decline in plant productivity (Buchanan-Wollaston, 1997). Cellular membranes, which are responsible for cell structure, cell-to-cell signaling, and compound transport, are also degraded (Taiz and Zeiger, 2002). Catabolites generated from the processes of leaf senescence may be transported or remobilized from aging leaves to other parts of the plant to support the growth of non-senescent organs during natural leaf senescence. Although leaf senescence is an important survival mechanism for the entire plant system, premature leaf senescence induced by environmental stress can lead to the reduction of plant growth and productivity.
