A QUANTITATIVE EVALUATION OF ONE ASPECT OF FROST HARDINESS IN ALFALFA

Abstract

Root tissue excised from alfalfa cultivars (Medicago sativa L. and M. media Pers.) was studied to determine the relationships between impedance, living cell count, and duration of low temperature treatments. The effect of sucrose concentrations on these relationships was also examined. Higher impedances were closely associated with a high degree of cell survival. Cold-conditioning was found to increase impedance values; treatment with sucrose gave a further increase. Highly significant correlations between duration of cold treatment and mean living cell count, duration of cold treatment and impedance, and mean living cell count and impedance were found in six cultivars. Those cultivars which showed greater frost hardiness under field conditions gave higher tissue impedance values and greater cell survival in the presence of sucrose than did the frost-susceptible cultivars. The possibility of using response to sucrose treatment as a means of selecting for frost hardiness was considered.