Pattern of growth and 14C-assimilates distributions in relation to photosynthesis in radish plants treated with growth substances

Abstract

In a series of radish plants, with very thin hypocotyl and with a normal storage organ, the rates of photosynthesis, photorespiration and dark respiration did not differ. Therefore, the conclusion may be advanced, that translocation to the swollen hypocotyl is not determinated by the photosynthetic productivity, but rather the by storage capacity. To check it this is connected with an unbalanced hormonal content, plants were treated with lanoline paste, with IAA, GA₃, zeatin and all three in mixture or with injections of GA₃-water solution into the swollen hypocotyl. In young radish plants, with high rate of growth of aerial parts, treatment with the above mentioned substances stimulated ¹⁴CO₂-assimilation and increased retention of assimilates in ¹⁴C-donors, probably owing to retardation of their senescence. It increased the competition for photosynthates between shoot and storage organ. In older plants, in the stage of accumulation of nutrients in the swollen hypocotyl, IAA +GA₃+zeatin did not affect ¹⁴CO₂-assimilation, but in plants treated with growth regulators separately, assimilation decreased; IAA and GA₃ stimulated transport and accumulation of labelled substances in the swollen hypocotyl. On the basis of experimental data the conclusion may be advanced that responsiveness of the particular organs and processes to growth regulators depends on the stage of plant development. Phytohormone did not changed quantitatively the pattern of ¹⁴C-assimilates distribution. They stimulated processes with preference for particular stages of development.