Effect of abscisic acid on the photosynthetic oxygen evolution in barley chloroplasts

✍ Scribed by Liliana T. Maslenkova; Yuli Zanev; Losanka P. Popova

• Publisher: Springer
• Year: 1989
• Tongue: English
• Weight: 477 KB
• Volume: 21
• Category: Article
• ISSN: 0166-8595
• DOI: 10.1007/bf00047174

✦ Synopsis

In vivo effect of abscisic acid (ABA) on photosynthetic oxygen evolution was investigated in barley chloroplasts. The most important kinetic parameters of 02-producing reactions were changed. The results show inhibition of the O2-flash yields at ABA concentrations of 10/zmol/1 and 100/zmol/l and an increase in the degree of damping of the oscillations. ABA has a marked effect on the distribution of the oxygenevolving centers in So and S~ states and on sum of the centers (So + Sl) estimated according to the Kok model. In addition, the amplitude and the shape of the initial oxygen burst under continuous illumination are also significantly altered. At a concentration of 100 gmol/l, ABA strongly inhibits Hill reaction activity measured by DCPIP reduction. The results cannot be explained by the hypothesis of socaUed "stomata effect". On the other hand, no effects were observed on the investigated parameters in experiments involving ABA applied in vitro to isolated chloroplasts. It is hypothesized that ABA disrupts the granal chloroplasts structure and raises the degree of participation of the cooperative mechanism of 02-evolution connected with the functioning of PS IIa centers in the stroma situated thylakoids.