Figure 3. Regulatory pathways and plasticity of leaf senescence.
Multiple pathways that respond to various autonomous and environmental
factors are possibly interconnected to form a regulatory network.
In such a model, a single gene mutation that inactivates one
component of the pathways may not have a significant effect on the
progression of senescence. Question marks (1) represent genes that
are induced by a particular signal but may not play a role in leaf
senescence.