Control of synthesis of RNA and protein in subcellular fractions of Rhoeo discolor leaf sections by auxin and kinetin during senescence

Abstract

Both auxin and kinetin prevent senescence of sectiond of just-expanded leaves of Rhoeo discolor maintained in darkness for ca. 20 days. Auxin, but not kinetin, has a similar effect in more mature leaves. The effect of auxin (α-naph-thalene acetic acid), kinetin (6-furfurylaminopurine) and mixtures of both, applied in vivo to tissue sections, on synthesis of RNA and protein was assayed in three subcellular fractions. Auxin stimulates RNA and protein synthesis in mature and just-expanded leaves, while kinetin is only effective in the latter. The effect of both auxin and kinetin on enhancement of RNA and protein synthesis varies among different subcellular fractions, and auxin- or kinetin-induced synthesis of protein in a fraction never occurred except attending auxin- or kinetin-induced synthesis of RNA in that fraction. The stimulating effect of auxin on RNA and protein synthesis increases with increase in concentration from 0·1 to 25 p.p.m., while an optimal effect of kinetin is apparent at about 3 p.p.m. Kinetin greatly augments the auxin-induced synthesis of RNA and protein in all subcellular fractions. The possible mode of action of auxin and kinetin is discussed.