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increased (Bukhtoiarova et al. 1997). Massardo et al. (2000)
demonstrated that higher metabolic rates and less oxidative
damage were associated with the tolerant genotype to cold
temperature during germination, as cold temperature causes
a slow metabolic rate and high oxidative damages in sensitive
genotypes.
On germination of rice seed, the polyamine concentration
was greatest after 24hrs. and the arginine decarboxylase
showed a peak after 48 hrs. (Sen et al. 1981). However, under
stress condition the polyamine concentration increased over
the control.
In rice seeds (cv. Tapei 309), the content of free amine and
putrescine, spermidine, spermine and tyramine were higher
in seed lots having a low germination frequency compared
to those with high germination potential. In seeds with high
germination potential, conjugates decreased drastically during
germination, with an early and rapid increase in free amines. It
is suggested that amines are involved in the germination process
of rice seeds. It appears that amine conjugates may serve as a
storage form of amines which, upon enzymic hydrolysis, could
supply the cell with an additional amine reserve and infl uence
cell division and/or cell elongation (Fig. 8).
Protein phosphorylation
Conformational transition(DNA)
Ion balance
Prevention ofsenescence
Radical scvenging
Membrane stabilization
Regulation of gene Expession
Polyamines
in
rice seed
of
Fig. 8
Model for the regulations of polyamine metabolism in response to stress in
rice.
