The influence of glume pubescence on spikelet temperature of wheat under freezing conditions

Synthetic hexaploid wheat lines possessing pubescent glumes were observed t o suffer less frost damage during flowering than non-pubescent plants, afte r experiencing a damaging frost in the field during April 1997. In order to test the potential advantage conferred by glume pubescence, pubescent and non-pubescent plants were selected from a collection of synthetic hexaploid wheat lines, as well as from F-4-derived F-7 lines selected from crosses b etween pubescent synthetic parents and non-pubescent elite spring bread whe at lines. Comparisons of floret temperature between pubescent and non-pubes cent plants were carried out in a controlled temperature chamber. Freezing was determined by the appearance of an exotherm, the point in time at which water changed from liquid to solid phase. Flowering plants grown in pots w ere subjected to a 6-h period of temperature change ranging from 20 to -4 d egreesC. Floret temperature was measured using micro-thermocouples attached to a data logger. Results indicated that the temperature of pubescent flor ets was higher than that of their non-pubescent equivalents. Significant te mperature differences between the florets of pubescent and non-pubescent pl ants varied between 0.25 and 0.47 degrees C when the floret temperature of non-pubescent plants reached 0 degrees C. The appearance of the exotherm wa s delayed by as much as 3.27 min when pubescence was present. Pubescent pla nts also produced a higher number of grains per spikelet compared to non-pu bescent plants. These observations suggest that glume pubescence is a facto r that will influence the damaging effects of frost at or following anthesi s.