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Figure 2. A speculative model relating afterripening, class I
ß-1,3-Glucanase (ßGLU I) and endosperm rupture.
According to the model, ßGLU I, which is transcriptionally down-regulated
by ABA, contributes to endosperm wall weakening and breaking of coat-enhanced
dormancy. ABA accumulated during seed maturation is sufficient to delay
ßGLU I induction and endosperm rupture. Afterripening decreases
ABA levels and possibly sensitivity to ABA allowing the induction of ßGLU
I during imbibition, which helps modulate coat-enhanced dormancy. The
model does not exclude the possibility that other factors contribute to
afterripening and modulation of coat-enhanced dormancy, or that ABA has
additional functions, e.g. in photodormancy.
© Leubner-Metzger and Meins,
Plant J 23: 215-221 (2000)
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©
Blackwell Science