the leaves of `` '' moderately hardy '' '' ( spinach ) , `` '' very hardy '' '' ( ivy ) and `` '' extremely hardy '' '' ( spruce ) plants [ classification according to levitt { 1980 ) ] show characteristic differences with respect to changes in membrane lipid composition and chloroplast ultrastructure which are correlated with the degree of the frost resistance achieved by each type of tissue during adaptation to sub-zero temperatures .
C1521970
characte
C0039476
temper