MODULATION OF GRAIN DORMANCY IN BARLEY BY VARIATION OF PLANT-GROWTH CONDITIONS

Development of grain dormancy in four two-row barley varieties has been studied under nine different growth conditions in a phytotron. Plants were grown under the same condition of 16 hours at 15-degrees-C and 8 hours at 10-degrees-C with 24 hours of light, till anthesis and then transferred to a higher or a lower temperature regime in combination with different photoperiods. Grains were harvested at yellow and full ripeness and germination tests were performed at 10-degrees-C and 20-degrees-C. The variety 'Domen' and its descendant 'Kristina' were almost insensitive to the different temperature and light regimes. The other two varieties, 'Triumph' and its descendant 'Vicky', were very sensitive to the different climatic conditions during grain development as regards the dormancy levels obtained. Low temperature and short daylengths increased the amount of dormancy. Different germination tests revealed that none of the 'Triumph' grains germinated if the harvest was from plants which had been transferred to a cycle of 8 hours light at 14-degrees-C and 16 hours darkness at 10-degrees-C. The lowest amount of dormancy was obtained with continuous light at low temperature followed by a high temperature during the mealy ripening stage.