Agriculture Reference
In-Depth Information
products transported to different parts of the growing plants for
use in biosynthesis. The breakdown of proteins in germinating
seeds and in various parts of the plant is accomplished by the
activities of proteases and peptidases. Cellular protein patterns
change both quantatively and qualitatively with changes in
environmental conditions. Limited proteolysis and competing
polypeptide degradation are a closely interacting process
(Muntz 1996).
Seeds storage proteins in rice are essentially globulins
which are formed in the specifi c storage tissue, the endosperm,
during seed development. While these proteins accumulate
in the respective organs, storage tissues become nitrogen,
carbon sinks and acts as a nitrogen and carbon source when
the protein reserves are reactivated. Within the changing sink/
source relationship the formation and degradation of proteins
is unique, and plays important role in manifestation of plant
growth and development.
Cold stress in rice delays germination and emergence; soil
temperature of below 10ºC can result in complete failure of
germination (Yoshida 1981b). Screening for cold tolerance based
on germination and seeding growth have been attempted in
rice as well (Cruz et al. 2006) and there was marked genetic
variability for the traits (Satya and Saha 2010). Yoshida (1981b)
studied the effect of cold stress at three phases; germination,
imbibition, activation and post germination growth. The
effect of cold stress was more pronounced at the phase of
imbibing and this was regarded as the most sensitive phase.
The exposure of seeds to cold stress during this phase has
resulted in increased escape of solutes from the seeds. This
has been attributed to the incomplete plasma membrane of
the dry seed and the disturbance caused on its reconstruction
(Cruz et al. 2004). Cold stress at this stage has been reported
