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

Abstract

N. 1982, Changes in the level of endogeoous cytokinin-Iike substances in Acer pseudoplatanus embryos during stratification and gennination. -Physiol. Plant. 54: 318-322.The bioassay used to detect and quantify cytokinin activity was ihe Amaranthus test. Free cytokinin-like substatices in embryos ol Acer pseudoplatanus L. fruits increased duritig 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.Additional key-words -Amaranthus test. A. Julin-Tegelman {reprint requests),

CHANGES IN ABSCISIC ACID LEVELS DURING AFTER‐RIPENING AND GERMINATION OF ACER PLATANOIDES L. SEEDS

“…There was, however, some increase after 24 h. This represents the time at which the levels of endogenous promotory hormones are increasing in many germinating seeds (Tillberg, 1977;Von SchirachSzmigiel, 1979;Tillberg and Pinfield, 1981;Julin-Tegelman and Pinfield, 1982), although it is not clear why an essentially inhibitory compound like ABA should increase at this stage of apparently active growth. It may represent a response by the embryo to stress induced either by removal of the testa, or by transfer from 5 °C in the dark to 20 °C in the light.…”

Seed dormancy in Acer: Is there a common mechanism for all Acer species and what part is played in it by abscisic acid?

“…Many reports indicate that honnonal control is an important feature of dormancy in many Acer species of both types (Webb et al 1973, Tomaszewska 1976, Pinfield and Davies 1978, Julin-Tegelman and Pinfield 1982, and complex pattems of fluctuations involving several different hormonal components accompany exposure of intact fruits to inductive low-temperature treatment (Webb et al 1973 Pinfield andDavies 1978). One important component of the hortnone complement is ABA, and although the correlation between ABA levels and seed donnancy has not always been demonstrated convincingly (Black 1980, Walton 1980, ABA has been implicated as an inhibitor of germination in a number of instances (Webb et al, 1973, Tillberg and.…”

Appearance of the zeatin riboside type of cytokinin inPinus sylvestrisseeds after red light treatment

“…Grand Rapids, Barzilai & Mayer (1964) found cell division promoting substances, particularly after 48 h germination. The same coincidence between increased cytokinin activity and radicle emergence has been documented also for a number of photoinsensitive species such as Acer (Julin-Tegelman & Pinfield, 1982), and Rosa (Julin-Tegelman, 1983). Thus the increase in ZR found in the present work must be regarded as an after-effect of R treatment.…”