St. Lewak

The role of lipases in the removal of dormancy in apple seeds.

SummaryIt was found that the temperature optimum for apple (Malus domestica Borb.) seed acid lipase is the same as that for seed after-ripening process. The activity of the enzyme occurs between the 40th and 70th days of stratification, whereas the activity of alkaline lipase very low at that time appears about 20 days later. The changes of both enzyme activities were also studied during dark and light culture of embryos isolated from seeds after different times of stratification. Only the alkaline enzyme activity is under the control of light. It was concluded that essentially the same process, i.e. the hydrolysis of reserve fats is catalysed by two different enzymes: acid lipase acting during the cold-mediated breaking of embryo dormancy and alkaline lipase acting during the germination of dormant embryos, thus being under light control.

Morphological aspects of apple seedling early development in relation to embryonal dormancy

The growth of root, hypocotyl and cotyledons was measured in apple seedlings cultured for nine days from embryos isolated from seeds after various periods of after-ripening. Greening of the cotyledons was taken into account and the chlorophyll content determined as well.Embryonal dormancy results in anomalies already appearing in the early stage of development. They are manifested by differentiated greening and uneven growth of cotyledons, as well as by hypotrophy of root or hypocotyl. The frequency of those anomalies in the population decreases during the removal of dormancy, and therefore it may be accepted as the criterion of its depth.

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.

The Role of Proteolytic Enzymes in the Release From Dormancy of Apple Seeds

Summary In apple embryos isolated from seeds after different periods of cold stratification and in embryos cultured for 10 days at 5°C or 20°C in the dark, the proteolytic activities towards 10 synthetic substrates were determined. The results of these determinations allowed us to distinguish three groups of activities reaching maxima at different times of after-ripening. Only one of the activities studied that hydrolyzing L-cystine-di-β-naphthylamide (CysβNa), showed the temperature optimum at 5°C and was induced by low temperature. A massive proteolysis of storage proteins in the catabolic phase of seed after-ripening could be inferred from changes of the proteolytic activities. It was not directly temperature mediated. On the contrary, processes initiated by the hydrolytic activity towards CysβNa seemed to play an important role in the primary mechanism of dormancy release.

The influence of cytokinins on apple embryo photosensitivity and acid phosphatase activity during stratification

Kinetin (KIN) and benzyladenine (BA) stimulate to different extent the germination of apple embryos isolated from dormant seeds or seeds submitted to stratification. KIN is much more active in the replacement of light requirement in apple embryos germination. Both cytokinins decrease the photosensitivity of embryos isolated from the seeds stratified less than one month, but only BA accelerates the appearance of the second photosensitivity maximum, normally occuring on the 70th day of stratification. Both cytokinins stimulate the activity of acid phosphatase between the 30th and 50th day of apple seed stratification. The stimulation between the 50th day and the end of stratification is exerted only by KIN.These differences allow to discuss the specificity of action of particular cytokinins during the after-ripening and germination of apple embryos.AbstractKinetin (KIN) a benzyladenin (BA) stimulují různou měrou klíčení jabloňových embryí isolovaných z dormantních semen anebo ze semen podrobených stratifikaci. KIN je mnohem aktivnější při nahražení požadavku na světlo při klíčení. Oba cytokininy snižují fotosensitivitu embryí isolovaných ze semen stratifikovaných méně než jeden měsíc, ale pouze BA urychluje objevení se druhého maxima fotosensitivity, které se normálně vyskytuje po 70 dnech stratifikace. Oba cytokininy stimulují aktivitu kyselé fosfatázy mezi 30 a 50 dnem stratifikace jabloňových semen. Mezi 50 dnem a koncem stratifikace má stimulační účinek pouze KIN.Tyto rozdíly umožňují úvahy o specificitě účinku jednotlivých cytokininů během zrání a klíčení jabloňových embryí.

The Role of Abscisic Acid (ABA) in Regulation of Some Photosynthetic Enzyme Activities in Apple Seedlings in Relation to Embryonal Dormancy

Summary Changes in RuDPC and PEPC activities were investigated in non-dormant apple embryos grown in water as well as in solutions of abscisic acid (ABA) at various concentrations. At all concentrations applied ABA caused a decrease in ribulose-1.5-diphosphate carboxylase (RuDPC) activity and an increase in phosphoenolpyruvate carboxylase (PEPC) activity. These effects were correlated with a decrease in germinability as well as with a decrease in growth rate and a decline in chlorophyll content. The results reported suggest that endogenous ABA in dormant embryos regulates the carboxylating enzyme activities and chlorophyll content.

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.

Phloridzin transformation and accumulation during the stratification of apple seeds and the culture of isolated embryos

Phloridzin level and phloridzin β-glucosidase activity were estimated during apple seed cold stratification and during the culture of apple embryos isolated from seeds after different times of stratification. Both these factors were found to increase parallel to the progress of stratification as well as to the increasing ability of seeds/embryos to germinate. However, in the seed coats phloridzin dissappears during the progress of stratification despite the increasing β-glucosidase activity.Phloridzin formation in the embryos is postulated to be under light and gibberellin control, when isolated embryos germinate, and under temperature and gibberellin influence during the cold stratification of the seeds. The same factors control β-glucosidase activity development, which is also stimulated by the substrate itself. It is postulated that phloridzin accumulation and its glucosidase activity are indirectly related to the after-ripening process and directly to the germination of the embryos.

Indolylacetic acid oxidase in dormant apple embryos

The IAA oxidase activity was studied during the culture of dormant apple embryos. The effect of different factors on this enzyme activity was investigated either by adding them to the reaction mixture or to the culture medium. Phloridzin was found to be the best phenolic cofactor. The development of IAA oxidase activity was stimulated by phloridzin and GA3. The properties of apple embryos IAA oxidase allow to postulate the presence of two enzyme systems able to oxidize IAA in the material studied. The involvement of peroxidase activity in IAA oxidation was also investigated. The differences in the changes of peroxidase and IAA oxidase activities during the culture of dormant apple embryos do not permit to consider the activity of peroxidases to be identical with that of IAA oxidase.AbstractByla sledována aktivita oxidázy IAA během pěstování dormantních jabloňových embryí. Vliv různých faktorů na aktivitu tohoto enzymu byl sledován bud jejich přidáním do reakční směsi nebo do kultivačního media. Bylo zjištěno, že floridzin je nejlepší fenolický kofaktor. Aktivita oxidázy kyseliny indolyloctové byla stimulována floridzinem a GA3. Vlastnosti IAA oxidázy jabloňových embryí prozrazují přítomnost dvou enzymatických systémů schopných oxidovat kyselinu indolyloctovou ve studovaném materiálu. Dále byla sledována závislost aktivity peroxidázy na oxidaci IAA. Rozdíly ve změnách aktivity peroxidázy a IAA oxidázy během kultivace dormantních jabloňových embryí nesvěděí pro identitu aktivity peroxidázy a IAA oxidázy.