Changes in the level of endogenous cytokinin‐like substances in Acer pseudoplatanus embryos during stratification and germination

Abstract

The bioassay used to detect and quantify cytokinin activity was the Amaranthus test. Free cytokinin‐like substances in embryos of Acer pseudoplatanus L. fruits increased during the first 20 d of fruit stratification at 5°C, but subsequently fell rapidly to values well below the amounts present in the embryos of freshly harvested fruits. These lower levels persisted throughout the remainder of a 60 d stratification period. Bound cytokinins fell during stratification from the highest detected levels present in freshly harvested material to values which were lower by about one third. No peaks of bound cytokinin activity were detected at any stage during stratification. In embryos from fruits stored at 17°C and unable to germinate, both free and bound cytokinins remained at a very low level throughout the 60 d period. Embryos from fruits previously stratified for 60 d showed increases in both free and bound cytokinins during the first 24 h of their incubation at 20°C in light, but after longer incubation periods up to 72 h, cytokinin concentrations decreased again to levels similar to those present at the commencement of the incubation period. Determinations conducted in 1979 and 1980 showed quantitative differences, but similar qualitative changes were observed in the two years. Most of the cytokinin activity was associated with compound(s) that co‐chromatographed with zeatin and zeatin riboside.