Agriculture Reference
In-Depth Information
The relationships between the rate of starch accumulation
and the activities of enzymes involving starch biosynthesis
in developing grains of fi eld grown rice cultivar Tainung 67.
The results indicated that the activities of most of the grain
showed their maximum between 7 to 14 days after anthesis,
but the sugar-starch conversion rose and reached their
maximum. The changes in the rate of starch accumulation
correlated well with the changes, in the activities of sucrose
synthase (SuS), invertase, hexokinase, soluble starch synthase
(SSS), granule bound starch synthase, pyrophosphorylase,
UDP glucose pyrophosphorylase, phosphoglucoisomerase,
phosphoglucomutase, AGP glucose pyrophosphatase, starch
debranching enzyme, during the grain fi lling period. The
rapid grain-fi ll and shorter grain fi lling were associated with
its higher activity of starch synthesizing enzymes of the short
duration rice variety at the early phase of grain development.
It is noted that starch accumulation is signifi cantly related
to invertase (0.52), hexokinase (0.54), phosphogluco mutase
(0.56), AG Pase (0.42), soluble starch synthase (0.67) and starch
branching enzyme (0.58) signifi cantly (Table 17).
Leaf sheaths of higher position leaves (upper leaf sheaths)
on rice (
Oryza Sativa
L.) stems function as temporary starch
storage organs at the pre heading stage. Starch is quickly
accumulated in upper leaf sheaths before heading, but the
storage Starch is degraded at post heading stage to provide
the carbon source for developing grains. Abscisic acid (ABA)
is a key plant hormone to control plant development and stress
responses. It was found that ABA content in upper leaf sheaths
was signifi cantly increased at the stage after panicle exsertion
and that the pattern of ABA increase was negatively correlated
with changes in starch content. Exogenous ABA reduced starch
content in leaf sheaths while the activities of starch degradation
