CONFOCAL PH-TOPOGRAPHY IN THE SHOOT APEX OF CHENOPODIUM-RUBRUM IN RELATION TO DIFFERENT PHOTOPERIODS

A short-day photoperiodic regime induces flowering in Chenopodium rubr um. The signal is perceived by leaves and transported to the target ti ssue, apical meristem, where morphological changes follow. Changes in the pH-values in the apical meristem after the inductive photoperiod w ere examined as a possible element of signal transduction in the targe t tissue. The pa-changes were visualized by means of a fluorescent cyt oplasmic pH-probe, carboxy SNARF-1. The tissue pH-maps were based on o ptical sectioning using a confocal laser scanning microscope. Specific changes in the cytoplasmic pH distribution were found 2 h after the e nd of inductive photoperiod: a shift to a more basic pH at the sites o f the subsequent initiation of new primordia and in the inner cell lay ers of the apex (corpus), as compared with the superficial cell layer (tunica). Different responses of tunica and corpus could reflect their different roles in vegetative development and inflorescence formation .