THE EFFECT OF IRRADIANCE ON THE PROTEIN SYNTHETIC MACHINERY OF VICIA-FABA L LEAVES

An increase in irradiance from 10 to 125 W/m(2) resulted in the activa tion of RNA polymerase I and recruiting of monosomes into polysomes in the leaves of Vicia faba L. Leaf discs from plants grown under 10 W/m (2) synthesised protein in vivo at a higher rate than discs from plant s grown under 125 W/m(2), especially when calculated per dry weight ba sis. The translation activity of polysomes in the cell-free system was also significantly higher in the preparations from plants grown under 10 W/m(2), A search for possible regulators of polysome translation a ctivity resulted in the detection of two major non-ribosomal polypepti des with M(r) of about 42 and 55 kDa in the polysome preparations. The abundance of these polypeptides depended on the irradiance and leaf a ge. Preliminary immunoassays and phalloidin test indicate the presence of polymeric actin in the polysome preparations.