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A Handbook of Biology
5 Abscisic Acid (ABA)
During mid-1960s, it was reported 3 kinds of inhibitors: inhibitor-B,
abscission II & dormin. They were chemically identical and now known
as abscisic acid.
ABA is the derivatives of carotenoids.
(AIPMT 2009)
It regulates abscission and dormancy.
FÜÑÇTÏØÑS
Inhibitor of plant growth and metabolism.
Inhibits seed germination.
Stimulates the closure of stomata in the
epidermis.
Increases the tolerance of plants to various
kinds of stresses. Therefore, it is also called
the stress hormone.
(AIPMT 2014)
For
seed
development,
maturation
&
dormancy (it helps to withstand desiccation
and other unfavourable factors).
In most situations, ABA acts as an antagonist
to GAs.
The role of ABA could be complimentary or antagonistic. These could be
individualistic or synergistic.
ÏÑTËRÅÇTÏØÑS ØF PGRS
PGRs play individualistic or synergistic role. Such
roles may be complimentary or antagonistic.
PGRs interact to affect dormancy in seeds/
buds,
abscission,
flowering,
senescence,
vernalisation
,
apical
dominance,
seed
germination, plant movements etc.
In most situations, ABA acts as an antagonist to
GAs. (NEET 2012)