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

Synthetic hexaploid wheat lines possessing pubescent glumes were observed to suffer less frost damage during flowering than non-pubescent plants, after 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 between pubescent synthetic parents and non-pubescent elite spring bread wheat lines. Comparisons of floret temperature between pubescent and non-pubescent 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 were subjected to a 6-h period of temperature change ranging from 20 to -4 degreesC. Floret temperature was measured using micro-thermocouples attached to a data logger. Results indicated that the temperature of pubescent florets was higher than that of their non-pubescent equivalents. Significant temperature differences between the florets of pubescent and non-pubescent plants 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 was delayed by as much as 3.27 min when pubescence was present. Pubescent plants also produced a higher number of grains per spikelet compared to non-pubescent plants. These observations suggest that glume pubescence is a factor that will influence the damaging effects of frost at or following anthesis.