Several parameters indicate the drop in activity. The most striking is maybe the reduction of the leaf size. In each shoot are the lowest leaves that have developed first larger than that at the tip. We discuss the transition to the reproductive stage in more detail in the context of flowering hormones. You will find more about this in the next section.
Senescence starts together with flower development.
During this stage are assimilates mobilized and used for seed development . The vegetative organs stop their metabolic activities successively and start to wither unless they are perennial. Withering parts fall off. The process described so far is mainly valid for annual plants, though part of it is also true for perennial plants. The organs of a perennial plant like a tree, for example, can be grouped into perennial organs whose part increases annually and those organs that live for just one growing season.