Jiří Šebánek

The Effect of paclobutrazol on the Level of endogenous IAA in Relation to the Rooting of Cuttings and Abscission of Petioles

Summary The relationship between paclobutrazol (i.e. Cultar) and β-indolylacetic acid (IAA) was studied. Immersion of the bases of Ligustrum vulgare cuttings into a 0.05% solution of Cultar stimulated rhizogenesis similarly as when applying a 100mgl-1 concentration of IAA. However, the degree of rhizogenesis was much higher if the cuttings were first immersed in a 0.05% solution of Cultar and then in a 100mg1-1 solution of IAA. Abscission of leafless petioles of Malus sylvestris was significantly inhibited when applying paclobutrazol (Cultar) to the distal cut surface of the excised leaf. The fact that the immersion of the bases of Ligustrum vulgare cuttings into a Cultar solution resulted in a statistically significant increase in the level of endogenous IAA in the basal parts of the cuttings could explain the above given effects on rhizogenesis and abscission.

Cotylar dominance in pea and flax seedlings with regard to growth regulators

Summary The growth of axillary buds (cotylars) was followed on decapitated pea seedlings with intact and reduced cotyledons. It was found that the production of dry matter of cotylars per 1 g of dry matter of cotyledons increased with the reduction of the mass of cotyledons. BA and GA promoted while IAA and TIBA reduced this production. BA applied on a naturally inhibited cotylar of decapitated pea seedlings induced a correlative reversal: the inhibited cotylar became a dominating one and vice versa . If the original size difference between cotylars was 12 mm, the correlative reversal was observed in 75 % of cases. If flax seedlings were deprived of one cotyledon, primary root and hypocotyl base the hypocotyl stump on the side of the remaining cotyledon bended due to an intensive growth. The application of IAA paste on the stump of the removed cotyledon established very often a growth (i. e. bending) balance between the effects of cotyledons and IAA paste: No bending of the hypocotyl stump occurred. This phenomenon was most frequent after the application of 0.12 % IAA paste.

Content of endogenous cytokinins in intact and transversally cut leaf blades of Bryophyllum crenatum

An increased growth of marginal buds on excised leaves from vegetative plants of Bryophyllum crenatum following transversal separation of leaf blades into three segments (apical, medial and basal) as compared with non-separated leaves, was associated with increased endogeneous cytokinin-like substances. This cycokinin increase can be demonstrated seven days after the separation and before the growth of marginal bud primordia. The level of endogenous cytokinin-like substances increases in a similar direction as the formation and growth of marginal buds, from the base of leaf blade to its apex.ZusammenfassungDer Anstieg von Marginalknospenbildung an den von den vegetativen Pflanzen Bryophyllum crenatum isolierten Blättern, der durch eine Querteilung der Blattspreiten in drei Segmente (apikales, mittleres und basales) gegenüber den intakten Kontrollblattspreiten nachweisbar ist, ist mit dem Anstieg der endogenen Zytokininähnlichen Stoffe verknüpft. Diesen Anstieg des Zytokininspiegels in der geteilten Blattspreite, gegenüber der intakten, kann man binnen sieben Tage nach der Querteilung der Blattspreite beweisen, d.h. in der Zeit vor dem Wachstum der Marginalknospenanlagen. Der endogene Zytokininspiegel steigt dabei von der Basis zum Apex der Blattspreite an, ähnlich wie die Marginalknospenbildung.

Release of cotyledonary shoots of pea (Pisum sativum) seedlings from inhibition as related to endogenous zeatin and ethylene and exogenous IAA and benzyladenine

This paper deals with apical dominance using a dicotylar model obtained after decapitation of pea seedlings with two shoots — one dominant and the other inhibited. When the dominant shoot was decapitated the inhibited one is released from inhibition and after 24 to 72 h begins to grow. However, the levels of trans-zeatin and production of ethylene increase within 4 and 6 hours respectively after release from inhibition, and within an interval of 72 h the levels of both phytohormones begin gradually to decrease. This indicates that also in this model, the release from apical dominance is associated with an increase in the level of cytokinin zeatin and, thereafter, also with an increased production of ethylene. If indolyl-3-acetic acid (IAA) is applied on the decapitated main stem after decapitation of the dominant shoot, the growth of the initially inhibited one is very strongly retarded; if, however, IAA is applied on the decapitated dominant shoot, this inhibition is significantly weaker. This means that the inhibiting effect of IAA on the inhibited shoot originates to a greater degree from the main stem rather than from the dominant shoot. The effect of benzyladenine (BA) is transferred equally from the decapitated main stem and from the decapitated dominant shoot because the initially inhibited shoot begins to grow as well as also other shoots from serial cotyledonary buds.

The effect of jasmonic and 2, 3, 5-Triiodobenzoic acid on the correlation between cotyledons and their axillary buds in flax Linum usitatissimum and Pea Pisum sativum seedlings

Summary Effects of jasmonic and 2, 3, 5-triiodobenzoic acid on growth correlations were investigated concerning cotyledons and their axillary buds in flax ad pea seedlings which have been decapitated above the cotyledons. In the case of intact cotyledons, both acids applied on one cotyledon could determine the dominance between axillary buds only in flax (epigeic cotyledons). In pea (hypogeic cotyledons) this effect was not observed. If one cotyledon is excised and the other remains intact, a promoting effect on the growth of axillary bud can be observed in flax, while in pea this effect is of inhibitory character. The promoting effect of flax cotyledon cannot be removed by application of jasmonic acid to the remaining cotyledon. However, application of 2, 3, 5-triiodobenzoic acid to this cotyledon causes a growth-correlative reversal, because the bud of the remaining cotyledon is inhibited while that of the excised one is promoted to growth. In pea seedlings deprived of one cotyledon, triiodobenzoic acid applied to the bud of the excised cotyledon does not reduce its growth so that the growth of the axillary bud of intact cotyledon remains to be inhibited. On the other hand, a similar application of jasmonic acid shows an inhibiting effect on the growth of axillary bud of excised cotyledon so that the outgrowth of the remaining cotyledon is observed. This means that jasmonic acid shows a similar growth-correlative effect as abscisic acid (demonstrated earlier) and that this effect differs from that of 2, 3, 5-triiodobenzoic acid which is an antagonist of auxin.

Correlative Effects of Root and Basal Part of Stem upon the Content of Cytokinins in Leaves of Bryophyllum crenatum

Summary An unilateral transverse incision in the central part of Bryophyllum crenatum stem below one of opposite leaves released this leaf from correlative-promoting effects of the root and the basal part of stem. This resulted in a decreased level of endogenous cytokinins in the leaf sbove the incision (i.e. facing the opposite control leaf) within 24 h after the incision; however, the level increased again within 7 d, and marginal buds were formed within a period of 35 d.

Content of Endogenous Gibberellins in Pea Roots in Relation to their Polarity

Summary The highest content of endogenous gibberellins was found in the apical part of 3-day-old pea seedlings. In 6-day-old seedlings, an increase in gibberellin activity was observed in the root base; the formation of primordia of lateral roots was associated with a shift of maximum gibberellic activity into root bases.

Effect of β-indoleacetic acid on the level of 2-chloroethyl trimethyl-ammonium chloride in epicotyls of pea seedlings.

Summary A question of CCC content was solved in pea epicotyls treated with IAA in comparison with the control without exogenous IAA. In the epicotyls of variants treated with IAA a provable CCC decrease could be observed. For colorimetrical CCC assay a method was described utilizing a colour complex produced by dipicrylamine with CCC on paper chromatograms.