RNA synthesis in shoot apices and young leaves ofchenopodium rubrum during three dark periods of photoperiodic floral induction

Abstract

The rate of RNA synthesis in shoot apices of the short-day (SD) plantChenopodium rubrum was compared in three successive dark periods required for flowering.32P label was used for fractionation of RNA on slabs of polyacrylamide gels on mioroscopic slides. Incorporation of32P and3H-uridine into apices was followed using histoautoradiography under identical conditions for oomparison. The lowest rate of synthesis was found on the seoond day of induction. A slight increase was usually observed in the third dark period, possibly linked with the first anatomical and/or morphological changes whioh have appeared due to mduction. Most of the label was found in ribosomal BNA in this case. After the plants wero transferred from light to darkness RNA synthesis in the shoot apex decreased within three hours. There was good agreement between results obtained by eleotrophoresis and by histoautoradiography. All previous observations which have been obtained using cytophotometry and histoautoradiography were confirmed. The rate of synthesis of BNA in shoot apices is paralleled by that in primordial leavea. The marked rise of RNA synthesis during the inductive period, found in some planta requiring only single inductive cycle, was not established inChenopodium. A different pattern of RNA synthesis between plants flowering after one and after several dark periods, is suggested in discussion.