Levels of endogenous abscisic acid in achenes of Rosa rugosa during dormancy release and germination

Germination experiments on isolated embryos and intact achenes from Rosa rugosa L. var. rubra revealed the existence of both coat-induced and embryo dormancy. Studies were made on the quantitative changes in abscisic acid (ABA) of achenes during both a stratification period at 4°C and a subsequent germination period at 20°C. Controls were run in parallel at 17°C. Dormant, unimbibed achenes contained large amounts of ABA. The level fell rapidly during the early stages of stratification at 4°C, mainly due to leakage, and then the decline levelled off. The reduction of ABA content during germination was less and followed a tri-phasic pattern. Under the control conditions, the ABA level also fell although still faster, the amounts present being consistently below those detected in the corresponding cold-stratified samples. The content of alkali-hydrolysable ABA was low and not affected either by the duration or by the temperature of stratification. The investigation shows that termination of dormancy is not simply a consequence of a fall in the content of endogenous ABA and supports the current debate questioning the central role of ABA in regulation of dormancy breakage and of germination.