Changes in Ribonucleic Acid & Deoxyribonucleic Acid in Developing Orange Leaves.

The elucidation of chemical changes which are related to development an(I growth cycles is of primary importance in gaining inside knowledge of the fundamental processes associated with growth. Among the studies in this fieldl many reports were published on protein synthesis which. in particular, is indicative of the state of the over-all cellular activity. Thus, during active growth an(l cell enlargement protein synthesis is intensive (1, 21, 22, 33), while wvith aging and senescence the rate of synthesis slows down considerably (40) resulting in an actual drop in protein level of the tissues (22, 33). Intimately related to protein synthesis are nucleic acids (41) the levels of which are also closely associated with age (22, 39). Treatments of apple leaves with purine and pyrimidine bases affected their nucleic acicl metabolism in a way similar to that observed in agerelated phenomena such as flowering (16, 18) and leaf suitability to aphids (21, 22). The response of plants to environnmental factors as drought and cold, which are also age-dependent, hlas been recently found to be correlate(d to certain nucleoproteinous fractions (14, & unpublished data). More detailedl information on relations between proteins, nucleic acids and aging of plants is neededl. The present study deals wvith nucleic acids in growing orange leaves, both untreated an(d treated witlh purine and pyrimidine bases.