some metabolic changes making them receptive to stimulation by GA which then
promotes the synthesis of various hydrolases, but particularly a-amylase. This
is secreted into the starchy endosperm (C), and there hydrolysis of the reserve
starch commences (D). Some of the maltose and glucose released by amylolysis
may be converted to sucrose by the aleurone cells and transported as such to the
growing embryo, but most is absorbed directly through the scutellum where
sucrose is formed (F). If the production of these monosaccharide sugars exceeds
their rate of transport to, and utilization by, the growing embryo, they accumulate
in the endosperm. There they act as an effective switch to stop production of
further a-amylase (E), an enzyme whose activity in the endosperm already
exceeds the requirement for the products of its hydrolytic activity (i.e., sugars).