A “switch” is needed to terminate development and promote the transition
to a germination and growth program
Important role of seed environment: To maintain embryos in a developmental
mode until they are fully formed and have accumulated sufficient reserves to
permit successful germination and subsequent seedling establishment
Two key regulatory factors are:
- restricted water uptake via negative osmosis (water encourage germination)
- abscisic acid (ABA) (encourage seed development/maturation/reserve synthesis)
Evidence for role of ABA:
1. embryo culture
2. mutants exhibiting vivipary (premature/precocious germination)
3. preharvest sprouting cereals
Response mutants:
- abi3 in arabidopsis (mustard)
- vp1 (abi3 homolog) in maize
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