PROBING TENABILITY OF BIOCHEMICAL VIS-A-VIS PHYSICOCHEMICAL INTERPRETATIONS OF MODULATION OF RADIATION-DAMAGE BY CAFFEINE AND CYSTEINE IN BARLEY

Cysteine (an aminothiol) is known to protect against radiation damage, and is understood to do so by generating hydrogen peroxide which subs equently inhibits RNA synthesis. Our results showed inability of catal ase to remove or reduce the magnitude of radioprotection by caffeine a nd/or cysteine at optimal/suboptimal temperatures in barley. This obse rvation was adequately corroborated by data on frequency of chromosoma l aberration, peroxidase activity and total protein content. On the co ntrary, catalase tended to enhance the radioprotective effectiveness o f cysteine, Macromolecular synthetic patterns in caffeine and/or cyste ine treated embryos were too inconsistent to permit a logical conclusi on with regard to their positive involvement in the biochemical pathwa y of chemical modification of radiation damage. On the other hand, mut ually annihilatory reaction hypothesis based on physico-chemical princ iples provides a satisfactory explanation for the observed effects.