EFFECTS OF LOW-TEMPERATURES ON THE ACTIVITY OF SOME ORNITHINE CYCLE ENZYMES IN WHITE LUPIN (LUPINUS-ALBUS L)

The aim of this paper was to specify the nature and function of proteins whose metabolism is affected by low temperatures (4-degrees-C, 0-degrees-C) in white lupin. Cotyledons of two genotypes, a spring and a winter one, differing in sensitivity to cold, were analysed. The activity of arginase, urease and ornithine transcarbamylase were measured at different germination stages. The results showed that the activity of urease and of ornithine transcarbamylase in samples developed at 4 or 0-degrees-C were greatly reduced whereas that of arginase was maintained. The enzymatic responses of the two genotypes were similar, while those of the winter variety were slightly more emphasized in stressed plants. These changes in response of enzymatic activities to low temperatures may be related to polyamine metabolism.