First, it is possible the KNOX genes were ectopically expressed early in leaf development when the higher order branching actually developed, but were later down-regulated by redundant mechanisms, such as ASYMMETRIC LEAVES 1 (AS1 -mediated repression [ 57, 58].
These examples illustrate the principles involved in leaf development, but there are many deviations associated with variations in leaf form.
Thus, PLA1 and PLA2 play important roles in leaf development.
However, the genetic regulation downstream of the GA pathway in leaf development is poorly understood.
These factors explained the differences in the variation in leaf development on the same plant.
This provides evidence that the pure diffusion process establishes the formation of the long-range signaling gradient in leaf development.
Its higher expression in leaves than in other tissues suggests that its primary role is in leaf development, as mediated by the cellular and molecular functions mentioned above.
Senescence is the final step in leaf development, which accompanied with the turn yellow of leaf, photosynthesis decline and biomacromolecules degradation, including nucleic acids, proteins, plastid pigments, and fatty acids, and so on.
Best known for their implication in calyx inflation, MPF2-like genes pertinent to the STMADS11 clade of the MADS-box family exert their functions in leaf development, flowering time, inflorescence architecture and floral reversion to just name but a few.
In a study performed by Nagasaki et al. [14], the rice genes known as SHOOTLESS2 (SHL4/SHOOT4/SHOOT ORGandZATION2 (SHO1), and SHO1, encoding orthologs of the small RNA-associated Arabidopsis proteins RNA-dependent RNA polymerase 6 (RDR6), AGO7, and DCL4, respectively, were shown to play a role in leaf development through the ta-siRNA pathway.
This is not conclusive evidence of an overshoot in leaf development that stressed the trees in drier years but it does give some support to that hypothesis that an imbalance in leaf to stem growth ratios reduces tree vigor, making trees more vulnerable to disturbance.
