How repair to desiccation- and rehydration-induced dam-
age to membranes and organelles is achieved is unknown.
However, during the imbibition of cotton seeds, the amount
of N-acetylphosphatidylethanolamine, a phospholipid with
membrane-stabilizing properties, increases, as does that of
the corresponding synthase. These molecules may be in-
volved in maintaining or enhancing membrane integrity
(Sandoval et al., 1995).
Upon imbibition, the quiescent dry seed rapidly resumes
metabolic activity. The structures and enzymes necessary
for this initial resumption of metabolic activity are generally
assumed to be present within the dry seed, having survived,
at least partially intact, the desiccation phase that termi-
nates seed maturation. Reintroduction of water during imbi-
bition is sufficient for metabolic activities to resume, with
turnover or replacement of components occurring over sev-
era1 hours as full metabolic status is achieved (Figure 1).
One of the first changes upon imbibition is the resumption
of respiratory activity, which can be detected within min-
utes. After a steep initial increase in oxygen consumption,
the rate declines until the radicle penetrates the surrounding