Studies on Protein Synthesis in Tomato Cotyledons and Leaves. I. Protein Synthesis and Turnover in Intact Cotyledons and Leaves

Details of aseptic culture of virus-free tomato seedlings used in comparative in vivo and in vitro studies on protein synthesis are described. Developmental changes in the levels of DNA, RNA, protein and chlorophyll content of seedling cotyledons and leaves were recorded, and are related to protein synthesis. Incorporation of isotopically labeled carbon into protein was followed both by photosynthetic uptake of 14CO2 and by the uptake of 14C-amino acids through the roots. A marked stimulation by light of 14C uptake was observed, and the higher rate of 14C incorporation from 14CO2 than from 14C-amino acids into the protein fraction is discussed in relation to the pathways of protein synthesis in tomato leaves, and also with regard to protein turnover.