Agriculture Reference
In-Depth Information
Rice plants grown under low temperature during
reproduction phase and at fl owering, often showed a similar
trends of changes as that of inferior grains during grain fi lling
period in rice.
Under cold stress at the reproductive phase, the grain
sterility increases. Even the grain thus formed are either half
fi lled or three fourth fi lled in irregular shape thus decreasing
average grain weight. This might be due to the fact that cold
or low temperature in post anthesis period severely affecting
the translocation of reserve assimilates to the developing grain.
Thus the accumulated assimilates like soluble carbohydrates
and soluble nitrogenous compounds are being hindered to
partition from source to sink (Annomymous 1989). Also,
studies have shown that as the temperature decreases in hilly
areas, translocation of soluble sugar and phosphorus to the
developing grains gets affected adversely resulting in chaffy
grains (Ngachan et al. 2010).
Increased yields have been achieved by (1) increased
or extended photosynthesis per unit land area and (ii)
increased partitioning of crop biomass to the harvested
product. Increasing assimilate allocation to the reproductive
primordial so as to establish a large potential sink should also
increase total crop photosynthesis indirectly. Evidence in the
major grain crops suggests that by anthesis the capacity of
photosynthesis and that photosynthesis is not limiting during
grain fi lling. To use this surplus capacity it is suggested that
carbon and nitrogen partitioning to the reproductive meristem
be increased so as to establish a high potential grain number
and the potential for a large grain size. It is then expected that
additional photosynthesis will follow, either by a longer daily
duration of photosynthesis or by an extended leaf area duration
(Richards 2000).
