1- Department of Agronomy and Plant Breeding, College of Agriculture, University of Tehran, Karaj
31587-11167, Islamic Republic of Iran.
2- Department of Plant Sciences, University of Saskachewan, 51 Campus Drive, Saskatoon, SK., Canada,
S7N 5A8.
Abstract: (6007 Views)
Little is known about the levels and physiological role of endogenous abscisic acid
(ABA) during after-ripening and germination. Genetic variants for ABA content were
investigated to account for the role of ABA in the persistence of seed dormancy. In this
study, genotypic variation in ABA contents at Zadok’s Growth Stage 92 (ZGS 92), temporal
changes in ABA during two physiological stages (after-ripening and water uptake),
and responsiveness of wheat seed to applied ABA at different concentrations, of two
tetraploid and two hexaploid wheat genotypes were examined during 1996 and 97. A
combined analysis of variance indicated no significant differences in ABA among genotypes
at ZGS 92. During the early stages of germination, endogenous ABA in the caryopses
of the four wheat genotypes was analyzed. The results showed a transient increase in
ABA content (up to 4 hours) occurring first during imbibition, followed by a decline up to
12 hours and an increase thereafter. ABA declined in all genotypes during seven weeks of
after-ripening (dry storage). The four genotypes had reductions in ABA up to 4 weeks of
after-ripening. An increase in ABA was observed during the fourth and fifth weeks of after-
ripening with a decline after seven weeks. ABA had a little effect on germination index
at the lower temperature (10 °C). Our results suggested that wheat grains are able to synthesize
ABA during imbibition. However, no significant differences between dormant and
non-dormant genotypes were detected. A decrease in ABA during after-ripening could
have a role in loss of seed dormancy.
Subject:
Agronomy Received: 2010/05/15 | Accepted: 2010/05/15 | Published: 2010/05/15