In the past, it was believed that when a developing plant made the decision to break seed dormancy and germinate, it would begin blossoming without restraint. However, the new research shows that a second checkpoint exists so that, for example in the case of the weed Arabidopsis, the plant has an chance to wait a bit before growing in case it is accidentally triggered to germinate by a cold summer's night. Arabidopsis is a weed in the mustard family that scientists already know a great deal about. It is a model system for the study of plant development because of a number of factors, including its small size and rapid generation time. In fact, they provide evidence that ABA activates a recently isolated Arabidopsis protein called ABI5 and show that this protein is crucial to the newborn plant's ability to protect itself against drought during this developmental delay.
ABA is a big part of both germination in young plants, and stress responses in adult plants.
The levels of ABA rise during germination and it has been shown to have an inhibitory effect on growth. Very simply, it keeps the plant from sweating so that it doesn't lose precious water. The ability of ABA to delay both germination and early growth was realized when Lopez-Molina and Mongrand found that seeds would in fact germinate after a certain period of time when grown in the presence of the hormone. They noticed, however, that the germinated plants did not green right away, and they later demonstrated that ABA could effectively block growth for up to 30 days. Since past studies showed that mutant Arabidopsis plants without the ABI5 protein grew without interruption after germination, the researchers wondered how this protein was linked to ABA's ability to maintain arrested germinated embryos.