Question

The timing of germination is very important for the survival of a plant species.

Under which circumstances would it be advantageous to have a non-functional GA/aleurone system?

Answer 1

Aleurone is a protein found in maturing seeds and tubers whic forms the outermost layer of the endosperm. aleurone cells remain alive at maturity. Several hormones influence the development of the aleurone layer, including auxin, cytokinin, abscisic acid (ABA), and gibberellin (GA). Auxin and cytokinin play a role in the earlier stages of aleurone development. The maturation of aleurone is promoted by ABA while germination is promoted by GA.

The timing of germination determines the post-germination conditions experienced by seedlings , including the competitive environment and can thus strongly affect the fitness, growth and survival of a species in a community and thus its invasion potential. Competition for resources is both affected by and affects the timing of germination.

The synthesis and secretion of these hydrolases (principally α-amylases) is under hormonal regulation. GA stimulates the synthesis and secretion of α-amylase and ABA reverses this effect . The GA enhancement of α-amylase production increases with the time of exposure to the hormone. Thus, once exposed to GA, the cells of the aleurone layer show detectable stimulation of α-amylase secretion after a lag time of approximately 8 h and this increase continues for 2 to 3 d. Increasing [GA] induces increasing α-amylase synthesis and secretion.