KURCHII, B.A. Institute of Plant Physiology and Genetics, 31/17 Vasylkivska Str., Kiev 03022, Ukraine. - (+S)-ABA) and (-R)-ABA are the final products from the oxidative cleavage of carotenoids.
The effects of diquat and ethephon (ethylene-releasing factor) on the
formation of abscisic acid (ABA) were studied. Based on our data we
have concluded that (+S)-ABA) and (-R)-ABA are the final products from
the oxidative cleavage of carotenoids. From the chemical point these
products are prooxidants. Biologically active form of ABA as an
antioxidant is 1',4'-diol ABA. These experiments precisely define the
role of 1',4'-diol ABA as being essential for the effective defense
against oxidative agents. By contrast, exogenous application of
(+S)-ABA) and (-R)-ABA as growth regulators demonstrated that these
chemicals act as oxidative agents like as phenols.To prevent oxidative
damages of the cellular biopolymers the cells increase the endogenous
levels of antioxidants including 1',4'-diol ABA, prostaglandins (PGE
and PGF). Hence, the increasing of endogenous concentration of
(+S)-ABA) and (-R)-ABA influenced by diquat (as also by another
stress) is the respond of living cells on the increasing of endogenous
quantities of oxidative agents. In this connection we concluded that
jasmonates are also the final products from oxidative cleavage of
membraneous lipids.
Key words: abscisic acid, carotenoids