UNE METHODE ENZYMOLOGIQUE A APPLIQUER POUR LA SELECTION DE PLANTES RESISTANTES AU FROID

Abstract

Freezing induced denaturation of cell membranes, as measured by the acid phosphatase method, was studied in cold-hardy Kharkov and non-hardy Champlein wheats. Denaturation occurs at an exponential rate and is irreversible under treatments that cause lethal damage to cells. Plotting the logarithmic values of enzyme units released per unit fresh weight against the reciprocal of the absolute value of temperature (°C) shows a linear segment of the curve (Z1 – Z2) with maximum slope. The TD-50, or mean denaturation temperature, corresponds to the inflection point on the curve and lies within this linear segment. The slope of this segment, expressed as log units per °C, was 0.246 and 0.346 for non-hardened winter wheat Kharkov and Champlein, respectively, while their TD-50 were equal at −3.7 °C. The slope of hardened Kharkov was 0.059, a fourfold decrease from its non-hardened value and one half the slope of hardened Champlein, with TD-50 of −10.7 and −6.4 °C, respectively. With cultivars grown in non-hardening conditions, the slope of the maximum rate of irreversible membrane denaturation is a very sensitive measure of the genetic capacity of plants to adapt themselves to cold stress. It is suggested that this method can be put to practical use in selecting plant cultivars for frost hardiness.