Increased DNA template and RNA polymerase associated with the breaking of seed dormancy.

Dormanit seeds of Hazel (Cworylus avellatta L.) re(luire a period of after-ripeniing at low temliperlat'ire before they beconme capable of subsequent germiination. (Gibberellic acid (GA;) c-n fully replace this requirement (2, 6). The identification of gibberellin-likz substar.s in extracts of chilled ( noni-dormant) seeds led Frankland and Wareiing (7) to suggest that gibberellin synthesis nmay be involved in the after-ripening process. GA, lhas also beeni sho -n to iniduce synthesis of hlydrolytic enzymiles in other seed tissues (13) and enhlanice RNA svynthesis in isolated nluclei of pea seedlings (9). Since derepression of genetic material has beeln shown to accompany the breaking of l)otato bud dormiiancy by ethylene chlorohydriii ('12) the possibility arises that the breaking of dormancy bv GA, ma similarly r .,ult in gene derepression. To test this possibility we have studied the effect of GA3 on chromatin-directed RNA synthesis in relation to the breaking of Hazel seed dormancy. All seeds were sterilized for 5 min in 0.5 % sodium hypochlorite, sowl1 on absorbant paper soaked witt. water or GiA;, '(1 ug/nil) and subsequently maintained at 25° in the dark for the required period. Embryonic axes were then excised by severing the cotyledonary ipetioles. KINA synthesis was measured y)V ,2O9 incorporation. Twenty embryonic axes were incubate(l f(r 3 hr in 1 nil of me(liutm (125 ,Lc ''1(4'1 % Sucrose an(l an() n\1 amonium acetate b)uffer, pH 6.0) at 250 and nucleic acids subsequently extr acte(l by the l)llenol-dupanol miethio(d of Cherry ct ild. (5). Polyacrylamnide gel electrophoresis was used to fractionate the RMTA specie:, (based on 1). alt'.:ough the data presented here represents total RNA. Gel electrophoresis also establislhed, on thle l)asis of molecular weight, that there was no significant incorporatiotn of label into bacterial RNA in any samples (unipublished data). Chromatin was prepared from emibryonic axes by general methods based on those of Huang and Bonner (8) and