EFFECT OF LIGHT CONDITIONS ON THE CONTENT OF PHENOLICS AND PAL ACTIVITY IN POPLAR CALLUS

Poplar (Populus alba L. ''pyramidalis'') callus cultures grown either under light conditions or in the dark gave different growth rates and maxima of fresh mass. The content of total ethanol-soluble phenolics i n the dark-grown tissues was lower during the whole 40-day growth peri od as compared with the light-grown ones. Under both conditions the co ncentration of ethanol-soluble phenolics changed, and two peaks of L-p henylalanine ammonia-lyase (PAL) activity were observed. Significant d ifference was found between both studied tissue types also in the grad ual raise of PAL activity in the illuminated tissues at later stages o f growth.