Seed dormancy in Acer: Endogenous germination inhibitors and dormancy in Acer pseudoplatanus L

Dormant seeds of Acer pseudoplatanus L. contain two zones of inhibition on paper chromatograms in "10:1:1" as detected by the lettuce and cress seed germination, and the wheat coleoptile bioassays. One zone at Rf 0.6-0.8 was partitioned into ethyl acetate at acid pH and was shown to contain ABA by its behaviour on GLC and isomerization under ultra-violet light. The other zone at Rf 0.9 was detected only in the germination bioassays and was partitioned into ethyl acetate over a range of pH indicating the presence of one or more neutral compounds.The inhibitors present in the embryo of dormant sycamore seeds inhibited the germination of non-dormant sycamore seeds at relatively low concentrations. A comparison with the effects of application of exogenous ABA indicated that endogenous ABA could not solely account for the inhibitory activity of seed extracts, which appeared to be due partly to the presence of ABA and partly to that of neutral compounds present in the embryo. Leaching treatments that removed dormancy led to a decrease in the level of inhibitors present mainly in the basic fraction. The exogenous application of kinetin to dormant sycamore seeds increased germination whereas gibberellic acid had no effect. Similar responses were obtained with lettuce seeds inhibited by the basic fraction of dormant sycamore seeds.It is suggested that an inhibitor-cytokinin interaction may be involved in the dormancy of sycamore seeds.