Biochemical effects of heat shock and caffeine on post-irradiation oxic and anoxic damage in barley seeds of low and high water content.
Wet heat shock (60 degrees C, 90 s) and caffeine (3.8 X 10(-4) M) afford significant radioprotection against post-irradiation O2-dependent damage which develops in seeds of approximately 3.5% moisture content. The damage was assessed in terms of seedling injury on the eighth day of growth. An increase in seedling injury is clearly seen, associated with a parallel increase in the peroxidase activity. There is a concomitant decrease in the content of total peroxides. Both these post-irradiation treatments potentiate the O2-independent component of seedling injury, irrespective of the seed moisture content. Analysis of the peroxidase activity in the seedlings using non-denaturing polyacrylamide gel electrophoresis reveals that two additional bands appear with the post-irradiation oxic damage. Radioprotection against this damage by caffeine, heat shock and O2-free post-irradiation hydration is accompanied by the disappearance of these two additional bands. However there is no appearance of the two additional bands in the peroxidase family even though the enzyme activity is substantially increased due to the action of caffeine and/or heat shock on the post-irradiation O2-independent pathway of damage. The probable mechanisms of radioprotection are discussed in this paper.
School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
S P
SP
Singh
P C
PC
Kesavan
D002110:Caffeine / Q000494:pharmacology*; D006358:Hot Temperature; D010100:Oxygen / Q000502:physiology*; D011835:Radiation Protection; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D012639:Seeds / Q000032:analysis / Q000187:drug effects / Q000528:radiation effects*; D014867:Water / Q000032:analysis
D011837:Radiation-Protective Agents; D014867:Water; D002110:Caffeine; D010100:Oxygen