needs to be subtly regulated (Stitt,
2004). The products can be stored as starch granules in chloroplast or
transported to where they are needed by sucrose transporter, or
assimilated.
The purpose of starch biosynthesis in plants is to provide a store of
energy. Many plants have evolved to store large quantities of starch.
For example, near 90% of the dry weight consists of starch in rice grain
(Tian et al., 2009). The detail of starch biosynthesis is, however, more
complicated than this – involving a number of enzymes – but can be
summarized as follows. The process starts with combining of glucose-
1-phosphate with adenosine triphosphate (ATP) to form adenosine
diphosphate glucose (ADP-glucose), catalyzed by the enzyme AGPase.