The involvement of programmed cell death in leaf senescence

The senescence of leaves is advantageous to plants as it allows nutrient resources to be moved from areas where they are no longer required to area where cell development processes are occurring. The leaf senescence process is under stimulus from both internal factors, such as signals from reproductive organs and environmental signals such as shade. The whole process is age dependent, and may occur at the same time as senescence occurs in other organs such is seen in monocarpic plants such as Arabidopis or in a more controlled manner, like is seen when plants such as Maize set seeds, or occurs when trees lose leaves in the autumn.

Genetically programmed cell death and leaf senescence

The destruction of cells is triggered by many external and internal stimuli, and is actively controlled by genetic processes. As leaf senescence is controlled genetic mechanisms it stands to reason that by association it is a form of programmed cell death. In leaves the death of cells does not occur all at once but starts in local patches. The process starts with the destruction of mesophyll cells , this is followed by the termination of other cell types.

Differences in programmed cell death in leaves and other processes

Programmed cell death is a common occurrence in plant developmental processes, for example it is used to protect from pathogen attacks and in the formation of tracheary components. However one of the main differences in leaf senescence is that cell death occurs at the whole organ level. Additionally the programmed cell death seen in leaf senescence allows for the distribution of nutrients to other parts of the plant (as opposed to simply destroying cells). This means that overall the mortality program occurs at a much slower pace in senescence than is seen in the processes previously mentioned.

The next section on leaf senescence will take a look into the structural changes that occur in the process.