Irena Sińska

Is the gibberellin A4 biosynthesis involved in the removal of dormancy in apple seeds

Abstract Changes in the gibberellin A4 (GA4) content during culture of isolated apple embryos are dependent on the stage of seed after-ripening. Similarly, the intensity of incorporation of labelled gibberellins precursor into the GA4 fraction depends to a high degree on the physiological state of seeds and correlates with the content of this hormone. The increase of endogenous GA4 level was observed during the culture of embryos isolated from seeds stratified shorter than 40 days. The intensive incorporation of [14C]-mevalonate into a fraction co-chromatographed with GA4 was stated during culture of such embryos. This incorporation was inhibited by 2-isopropyl-4-dimethylamino-5-methylphenyl-piperidinecarboxylate methyl chloride (AMO-1618), an inhibitor of gibberellins biosynthesis. The same treatment inhibits also the germination of embryos from seeds stratified for the same period. The suggestion was drawn concerning the role of the GA4 biosynthesis in the removal of embryonal dormancy of apple seeds.

Reinvestigation of apple-seed gibberellins

SummaryRe-investigation of the gibberellins in apple seed has established the presence of GA4 and GA7 and of traces of GA9. The fraction, previously considered to be GA7 by TLC, contains small amounts of GA4 and traces of GA9; and the fraction, characterized as GA4 by TLC, contains traces of GA7 and GA9. However the present results do not change the previous conclusions that during the stratification of apple seed the level of GA7 remains fairly constant while that of GA4 increases.

The Influence of Abscisic Acid on the Gibberellin Content in Apple Seeds During Stratification

Abstract.The content of endogenous GA4 and GA7 was determined in apple embryos cultured either on water or in the presence of ABA solution. The embryos were isolated from dormant seeds and from seeds removed from stratification which was effected either in water or in the presence of ABA. The influence of ABA on the decrease of two GAs levels was proved. The relation between the effect of ABA and the stage of stratification is closer in the case of GA4 than GA7. It is assumed ABA to inhibit the gibberellin biosynthesis.AbstractAutoři sledovali obsah endogenních giberelinů GA4 a GA7 v embryích jabloně pěstovaných ve vodě nebo v roztoku abscisové kyseliny (ABA). Embrya pocházela ze semen odpočívajících nebo ze semen stratifikovaných ve vodě nebo v roztoku ABA. Bylo zjištěno, že ABA vyvolává snížení obsahu giberelinů. Závislost mezi vlivem ABA a stadiem stratifikace bylo u GA4 výraznější než u GA7. Autoři předpokládají, že ABA inhibuje biosynthesu giberelinů.

Interaction of ethephon with cytokinin and gibberellin during the removal of apple seed dormancy and germination of embryos

Abstract Germination of apple embryos isolated from dormant and from partly stratified seeds was significantly enhanced by ethephon (E), benzylaminopurine (BA) and gibberellin A 3 (GA 3 ), and an additional increase of germination was observed when growth regulators were used in combination. The effect of all three growth regulators used separately or in combination was greatest for dormant and briefly stratified embryos, and diminish with stratification. BA and GA 3 counteracted the inhibitory effect of (aminooxy) acetic acid (AOA) and aminoethoxyvinylglycine (AVG) on embryo germination; the effect of BA was comparable to the effect of ethephon, while the effect of GA 3 was higher than that of ethephon treatment. BA increased ethylene evolution from dormant embryos from the first few days of their culture and the stimulation of ethylene synthesis preceded the increase of germination. GA 3 increased ethylene evolution only during the last days of embryo culture, when embryos already germinated in high percentage. Germination of dormant embryos inhibited by 2,5-norbornadiene (N) was restored within several days after its removal from embryo culture, and addition of E,BA or GA 3 increased speed of germination, GA 3 being the most effective. When growth regulators were present only during the first 5 days of embryo culture and N was applied after this period, the effects of E, BA or E + BA did not change during the next days of culture, but stimulatory effects of GA 3 or E + GA 3 were further increased. The results suggest that the effect of ethylene on the removal of embryonal dormancy is related to the action of BA, but not GA 3 .

Sensitivity of apple seed germination to light and some growth regulators

Experiments were aimed at checking whether the non-stratified apple embryos are sensitive to growth factors and light. The effect of growth regulators on light sensitivity was also studied. The stimulating or inhibiting effect of GA3, benzyladenine and IAA or coumarin on the dynamics of apple embryo germination was demonstrated. Seasonal fluctuations of the effect of the growth factors were noted. The stimulating effect of light on the germination of non-stratified apple embryos was demonstrated. This effect is independent of season and seems to be independent of the effects of growth regulators.AbstractPokusy byly zaměřeny na prověření citlivosti nestratifikovaných embryí jabloní k růstovým faktorům a ke světlu. Rovněž byl studován ůčinek rústovyeh regulátorů v závislosti na světle. Výsledky prokázaly stimulační nebo inhibiční účinek GAs, benzyladeninu a IAA nebo kumarinu na dynamiku klíčení embryí jabloní. V souvislosti s ročním obdobím bylo potvrzeno kolísání účinku růstových faktorů. Dále byl prokázán stimulační účinek světla na kličení nestratifiko-vaných embryí jabloní. Tento účinek není závislý na ročním období a patrně ani na účincích růstových regulátorů.