Dormancy and impotency of cocklebur seeds I. CO<sub>2</sub>, C<sub>2</sub>H<sub>4</sub> O<sub>2</sub> and high temperature

Abstract

High O2 tensions, CO4, C2H4 and high temperatures were effective not only in breaking the dormancy of cocklebur (Xanthium pennsylvanicum Wallr.) seeds but also in increasing the germination potential of the nondormant but small seeds. There were few qualitative differences in response to these factors between the dormant and impotent seeds. Unlike CO2, however, enriched O2 and C2H4 were stimulative even at the low temperature of 13°C. Germination induced by CO2, C2H4 and high temperature treatments was lowered when endogenously evolved C2H4 or CO2 was removed, whereas the effect of O2 enrichment was not affected by their removal. CO2 and high temperatures remarkably stimulated C2H4 production, whereas O2 enrichment had no such effect. C2H4 productivity was lower in the dormant than non-dormant seeds, suggesting that the after-ripening is characterized by increasing C2H4 production.