Abstract
The influence of seed coat modification and light quality on water
uptake and distribution in caryopses of dormant and non-dormant lines
of wild oat (Arena fatua L.) was determined using NMR microimaging.
Non-dormant seeds absorbed water more rapidly than dormant seeds
during imbibition on distilled water. This effect was detected first
in the embryo-scutellar region (8 h) and later in the proximal endosperm
(12 h). Cuffing the testa and pericarp close to the embryo or scarification
with KOH promoted rapid embryo/scutellum hydration and germination.
Cuffing at the middle part of the caryopsis did not enhance embryo
hydration nor did it greatly improve germination. The sensitivity
of water distribution to the phytochrome germination effect was examined.
Significant differences in imbibitional water uptake by embryoscutellum
tissue were detected by 18 h following redlight (germination promoter)
compared with far-red (germination inhibitor) treatment. The results
indicated that both the rate and the sequence of embryo/scutellum
hydration were important in initiating germination in dormant seeds.
A refinement of the model that describes water imbibition in wild
oat seeds during the early stages of germination is discussed.
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