Journal of Experimental Botany, Vol 49, 1203-1212, Copyright © 1998 by Oxford University Press
T Lin, W Yen and C Chien
The relationship between sugar content and loss of desiccation tolerance of
hydrated crop seeds (tomato, okra, snow pea, mung bean, and cucumber) was
evaluated by imbibing seeds with or without ABA, followed by dehydration
and germination. During the process of hydration, but before the seeds lost
desiccation tolerance, monosaccharide content increased only slightly,
sucrose increased in snow peas, mung bean and cucumber, but maintained its
original level in other species and the oligosaccharides declined
dramatically. At the time of losing desiccation tolerance, the sucrose
content of imbibed seeds was 2-3 times higher than the original level in
most species. Positive significant correlation coefficients
(r) were found in many, but not all crop seeds between
desiccation tolerance and the oligosaccharide mass, or oligo/sucrose ratio.
The ratio of oligo/sucrose in intact seeds at the time of losing
desiccation tolerance, however, was not a fixed value and varied among
species. Oligosaccharides declined significantly in different seed parts of
imbibed cucumber seeds while sucrose increased to a higher level in the
radicle than in the hypocotyl. Radicles were far more sensitive to
desiccation than hypocotyls. The same observation was found for cucumber
seeds imbibed in 100
ARTICLES
Disappearance of desiccation tolerance of imbibed crop seeds is not associated with the decline of oligosaccharides
Tree Seed Laboratory, Taiwan Forestry Research Institute, 53 Nan-Hai Road, Taipei, Taiwan; Corresponding author; e-mail: tpl@serv.tfri.gov.tw
M ABA, yet desiccation
tolerance was largely maintained in hypocotyls and cotyledons. It is
concluded that sucrose and oligosaccharides are not the determinants of the
loss of desiccation tolerance in hydrated seeds.Imbibed seeds did not show
any differences between seed parts in their ability to resynthesize sugars
during the process of slow dehydration. Differences in sensitivity to
desiccation among seed parts were not due to differences in the initial
water content or to the rate of water content increase among seed parts.
Physiological regulation of the loss of desiccation tolerance in crop seeds
during hydration is discussed.Keywords: Hydrated crop
seeds, desiccation, intolerance, oligosaccharide.
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