Abstract:
The effect of high light at 30 degrees C on chlorophyll fluorescence, xanthophyll cycle and abscisic acid (ABA) was determined to study the relationship of xanthophyll cycle and ABA in protection against photodamage. Sorghum seedlings of 8 days were grown on Hoagland medium supplemented with ABA (10 sup(-5) M) and photoinhibited at 2200 and 3600 mu mol m sup(-2) s sup(-1) PAR light intensities, and measurement of chlorophyll fluorescence (Fv/Fm ratio, qN, theta-PS II and theta-exc), xanthophyll cycle content and ABA content were made. The results obtained show that seedlings grown on ABA-supplemented medium had better energy dissipation (greater qN) and much greater level of de-epoxidation (high level of Z) than control seedlings. The level of endogenous ABA in seedlings grown on ABA-supplemented medium or otherwise remained the same. The results indicate a possible role of ABA in energy dissipation, probably by stimulating the xanthophyll cycle.
