Dormancy and Germination in Embryos of Hordeum vulgare L.—Effect of Dissection, Incubation Temperature and Hormone Application

The germination and growth of embryos from a genotype known to possess post harvest dormancy were examined. Samples of grain were taken at various times after harvest and tested under aseptic conditions for germination at a range of temperatures from 5 to 25 °C. They were incubated in water or in solutions of GA3 (2.5 × 10−5M), ABA (4 × 10−6M) or a combination of both GA3 and ABA. The effect on germination of the removal of the palea and lemma from the caryopsis, and the effect of isolating the embryo from the seed were also examined. At each interval the endogenous ABA concentrations of various parts of the grain were assayed. It was concluded first that the palea and lemma severely inhibit germination over the whole temperature range, secondly that the intact caryopsis has a particular optimum temperature for germination (10 to 15 °C) and thirdly that the isolated embryo does not show this sensitivity to temperature. The presence of GA2 in all cases stimulates germination and post germination growth, whereas ABA severely inhibits the response and indeed totally prevents germination in isolated embryos. Whereas this inhibition can be largely overcome for intact caryopses by addition of GA2 in the presence of ABA, growth of isolated embryos cannot be stimulated in this way. None of the samples tested showed any free ABA and it is therefore suggested that the endogenous ABA level cannot be the factor controlling post harvest dormancy.