CHANGES OF SURFACE-POTENTIAL AND PHOSPHOLIPID-COMPOSITION OF WINTER-WHEAT CALLUS CELLS GROWN AT 5-DEGREES-C AND 25-DEGREES-C

The surface potantial (Es), lipids content and the contents of main ph ospholipid fractions, i.e. PC, PE and PI, in callus from the mesocotyl part of mature embryo of winter wheat var. Grana have been estimated. Callus was obtained by the endosperm supported induction. Measurement s were repeated during callus vegetation at 25-degrees-C for 35 days o r at 5-degrees-C for over 50 days. The transfer of callus to cold caus ed a temperature stress and as result Es decreased almost twice. Howev er, during further growth of callus at low temperature a nearly linear increase of the potential took place. During this time small green ar eas with densely packed cells appeared. The surface potential of the c entres was different from that measured in the non-differentiated part of callus. Moreover, this potential was entirely independent of the t emperature and time of callus growth. Some evidences indicating that t he differences in the surface potential of callus cells precede the ap pearance of visible differentiating structures were also obtained. At 5-degrees-C the content of main phospholipid fractions initially grew and then their quantities distinctly diminished. During callus growth at 25-degrees-C remarkable differences in the concentrations of PC and PE were observed and only PI contents systematically lowered. A signi ficant negative correlation between PI concentration and surface poten tial (independent of temperature of growth) was obtained. As the diffe rentiation process in callus progressed, the percentage content of PE fraction was increased.