Endogenous Auxin Levels Research Articles

Auxin autotrophy and hyperauxinity of Eriophyes induced Zizyphus stem galls in Culture

Summary In contrast to Zizyphus normal stem tissue, the gall tissue was able to grow on HIS medium free of auxin and kinetin.With DL-tryptophan, both the tissues showed optimum growth at 5 mg/l, but the growth response of gall tissue was much higher.The optimal concentration of NAA and IAA was 10 mg/l for growth of both normal and gall tissues. In vivo , and in vitro grown gall tissues showed higher auxin contents as compared to normal tissues.The endogenous auxin level in both gall and normal tissues was highest in in vivo tissues, followed by DL-tryptophan, N AA, and IAA treatments in decreasing order.

Activities of Enzymes Relating to Starch Synthesis and Endogenous Levels of Growth Regulators During Tuberization of Isolated Potato Stolons Cultured In Vitro

Summary Changes in contents of starch and protein, and activities of enzymes relating to starch synthesis were studied during kinetin-induced tuberization of isolated potato stolons ( Solanum tuberosum L. cv. Irish Cobbler). During the initiation of tuberization, starch increased first, to a small extent, in the basal part of cultured stolons and thereafter in the apical part where the content continued to rise. Phosphorylase activity changed almost in parallel with the starch content. Activities of the soluble and the granule-bound synthetase were insufficient to account for the rate of starch accumulation. Activities of the latter were lower than the former at every stage of culture. On the other hand, endogenous levels of auxins, cytokinins and gibberellins were examined in the apical tip of uncultured stolons, and the tuberized tip and the basal part of cultured stolons. Both auxin and cytokinin levels were low in the tips of uncultured stolons. The cytokinin level was high in the basal part of cultured stolons, but not significant in the small tuber. The gibberellin was not detectable in these samples. These results were compared with those obtained for intact stolons and discussed for the conditions of starch deposition and tuberization in the potato plant.

Effects of Brassin‐Complex on Auxin and Gibberellin Mediated Events in the Morphogenesis of the Etiolated Bean Hypocotyl

AbstractThe excised, hooked bean hypocotyl was the system used to determine wheiher the ‘auxin‐ and gibberellin like’ effect of the lipoidal pollen extract, Brass in‐complex (Br), were mediated through, or independent of, auxin and gibberellin. The morphogenetic events of hook opening and hypocotyl elongation in this system are regulated by auxin and gibberellin, respectively.Brassin complex, like IAA, elicited a book closure in (he dark and retarded its opening in red light. This effect was synergized by T1BA, IAA and the presence of the auxin‐producing organs, the epicotyl and cotyledons. Br‐elicited hook closure was inhibited by the antiauxin. PCIB.Both GA3 and Br totally reversed the light inhibition of hypocotyl elongation. The GA3‐effect, but nol the Br elicited elongation, was overcome by Ancymidol. Hypocotyl elongation was partially inhibited by TIBA and PCIB. suggesting a possible auxin involvement also in this effect of Br.Br may elicit its growth responses through an effect on endogenous auxin levels, In this way it is different from other lipoidat growth regulators, such as the oleanimins which require the presence of exogenous growth regulators for activity.

An assessment of auxin-promoted transport in decapitated stems and whole shoots of Phaseolus vulgaris L.

(14)C-photosynthate transfer in decapitated stems of P. vulgaris plants, treated with IAA (indol-3yl-acetic acid), appeared, as ascertained by microautoradiography, to be restricted to cells of sieve-element appearance. The IAA-induced promotion of photosynthate transport was found not to depend on any artifacts caused by the decapitation procedure. Rather, decapitation primarily served the purpose of removing photosynthate sources above the point of hormone application which otherwise suppressed the expression of the IAA effect on acropetal photosynthate transport. Furthermore, by manipulating stem levels of endogenous auxins with the inhibitor of polar auxin transport, 1-(2(1)-carboxyphenyl)-3-phenylpropane-1,3-dione (ACP1.55), evidence was obtained indicating that photosynthate transfer to the shoot apex depended, at least in part, on endogenous levels of auxins at site(s) remote from the apical sink (i.e. shoot apex).

Ethylene and auxin-induced cell growth in relation to auxin transport and metabolism and ethylene production in the semi-aquatic plant, Regnellidium diphyllum

Cell elongation in the rachis of the semiaquatic fern Regnellidium diphyllum is induced by the addition of ethylene or indoleacetic acid (IAA). Experiments with whole plants or rachis segments have shown that ethylene-induced growth requires the presence of auxin. Ethylene does not cause a modification in either endogenous auxin levels or in the extent of auxin metabolism but auxin transport is reduced. Rates of ethylene production in Regnellidium are not altered by either mechanical excitation or by the addition of auxin. A two-hormone control of cell expansion is proposed in which an initial, auxin-dependent growth event pre-conditions the cells to a further subsequent (or synchronous) ethylene-dependent growth event.

インゲンの付傷によるこぶ形成と発育段階の関係

Wound-induced gall formation occurred only in bush kidney beans, and never in pole beans. Gall was formed most frequently at the site of injuries inflicted on the plant at the peak of reproductive processes. The plants at this stage produced more or less malformed leaf blades and petioles, i.e., distortion and/or bending. The level of endogenous auxin was also highest during the peak of reproductive processes and then declined gradually as the plants approached to normal senescence. Any of peas, soybeans, cowpeas, and broad beans did not respond to the mechanical wounding inflicted for the gall formation at any stages of plant development.

Evidence for a Gravity-Regulated Level of Endogenous Auxin Controlling Cell Elongation and Ethylene Production during Geotropic Bending in Grass Nodes

Experiments are described which indicate that geotropic bending in the node of the flowering stalk of the grass Echinochloa colonum results from a gravity regulation of endogenous IAA levels within the leaf sheath base. When the intact or longitudinally halved node is placed horizontally elongation is initiated in cells of the lower sides of the leaf sheath base, and is preceded by a rise in the level of extractable IAA. These events are followed by an increased rate of ethylene production. In halves in the upper position IAA content declines and ethylene production remains low. When halved nodes are reorientated from upper to lower or lower to upper positions IAA levels rise and fall respectively, cell elongation is initiated or repressed and ethylene production increases and decreases in concert. Addition or depletion of ambient ethylene or addition of an analogue of rhizobitoxin to repress ethylene production does not modify the geotropic bending response. Over a range of concentrations, application of IAA will enhance elongation of nodal tissue in vertical or upper positions but will either inhibit or have no effect on elongation of lower sides. The results are discussed in relation to the Cholodny-Went hypothesis of geotropism. We conclude that particular orientations of the leaf sheath base with respect to the gravity vector evoke rapid and highly localised changes in auxin metabolism, and the ensuing rises and falls in endogenous IAA levels control the initiation and repression of cell elongation.

Effect of Succinic Acid‐2,2‐Dimethylhydrazide on Endogenous Auxin Level in Apple Shoots

AbstractEndogenous auxin levels in the shoots of apple cv. Ingrid Marie (red mutant) treated with SADH (succinic acid‐2,2‐dimethylhydrazide) were measured. SADH was applied in aqueous solution at 12.5, 25 or 50 mM concentrations in June, 3 weeks after flowering. The defoliated shoot tips were analysed just before SADH spray and 7, 15, 30 and 60 days after spraying. Similar treatments had been made in earlier years.When analysed before the treatment of the year started, shoot extracts of control plants contained higher auxin level than those shoots which were to receive SADH treatment, indicating a residual effect of SADH treatmens during previous years. There was almost no auxin activity in the shoots analysed after 7, 15 and 30 days of SADH treatment. The control plants maintained a high level of auxin activity during this period. However, after 60 days of treatment, shoots treated with 25 or 50 mM exhibited higher auxin activity than control shoots. There appears to be no relationship between the SADH concentration and reduction in auxin activity in the shoots at early stages after treatment.

Correlations between the primary leaves and the cotyledonary-axillary buds of Phaseolus vulgaris L.

Correlations between the growth of the primary leaves and of the cotyledonary-axillary buds of 10 days old seedlings of Phaseolus vulgaris L. cv. Çali were investigated. The primary leaves of the plant, in which the effect of apical dominance had been overcomen, inhibited the development of the cotyledonary buds lying below them during a definite period of growth. The inhibitory period could be shortened if the primary leaves were covered by aluminium foil or if only a single primary leaf was left on the plant. The basipetal inhibitory effect of the primary leaves appeared to be additive and in accordance with the endogenous auxin level of the leaves and vanished when the auxin content fell below 2ppm/g fresh material. As regards the growth correlation of the primary leaves with their axillary buds, the primary leaves of 10 days old seedlings were observed to stimulate the growth of the axillary buds. When IAA was applied to the leaves through the petioles, the proper concentrations of endogenous auxin level in lamina stimulated bud growth. However, higher concentrations inhibited the growth of one of the buds and resulted in the dominance of the other. The primary leaves in this plant thus show correlative effects of a varying nature on the buds inserted at different positions on the plant.

Zur Regulation des Protonemawachstums von Athyrium filix-femina (L.) Roth

When protonemata of Athyrium filix-femina are treated with the antiauxin p-chloro-phenoxyisobutyric acid (PCIB) together with a cholinergic drug to reduce the sensibility to ethylene, cell elongation is clearly inhibited in red light, which leads partly to protonemata with extremly short cells, partly to an early transition from filamental to two-dimensional growth. In accordance with the results of experiments with phytohormones under different light conditions, this indicates that a supraoptimal level of endogenous auxin together with an increased sensibility to ethylene may participate in the stabilization of protonemal growth under red light.

Studies on the Regeneration of Apple Cultivars from Root Cuttings. II. Carbohydrate and Auxin Relations

SummaryThe effects of endogenous carbohydrate and auxin levels on shoot regeneration from apple root cuttings were studied in relation to season. Storage polysaccharides were estimated by periodate oxidation following organic acid hydrolysis. Maximum accumulation occurred in autumn (November) coinciding with the highest regeneration potential and survival rate of cuttings. Cold storage of cuttings (5°C) increased soluble sugars and subsequently accelerated callusing and shoot production. During regeneration polysaccharides were gradually depleted, whereas soluble sugars remained constant at their initial level (1–2 g/10 g residual dry weight). Cuttings started rotting at a polysaccharide level of approximately 3 g/10 g RDW. Fluorimetrie assay of endogenous IAA confirmed that auxin was directly involved in correlative inhibition of bud initiation and outgrowth. IAA moved rapidly and acropetally within detached root cuttings causing depletion and allowing preferential bud initiation to occur at the proximal...

Boron in Relation to Membrane Function in Higher Plants

The capacity for absorption of phosphate was shown to be reduced in Zea mays and Vicia faba suffering from boron deficiency; addition of 10−5 M boron rapidly restored this capacity. Root tips of normal plants also responded to the addition of boron during a short pretreatment period prior to the determination of phosphate absorption. Comparable effects of boron on the absorption of chloride and rubidium ions were also demonstrated in Zea mays. Specific inhibition of ion uptake by auxins may be relevant to the mechanism of the impaired ion transport seen during boron deficiency. The KCl-stimulated adenosine triphosphatase (ATPase) of the roots of Zea mays was also studied, with a view to examining the effect of boron deficiency on the activity of the enzyme. Boron-deficient roots had a reduced ATPase activity which could be rapidly restored by the addition of 10−4 M H3BO3 1 h before extraction of the enzyme. The results suggest that the activity of specific membrane components can be directly influenced by boron. Possible mechanisms whereby this control is exercised include direct interaction of boron with polyhydroxy components of the membrane and the elevation of endogenous levels of auxins. The evidence presented strongly supports the view that boron plays an essential role in the regulation of the functions of higher plant membranes and that the ATPase is a possible component of the transplant process.

ENDOGENOUS GROWTH REGULATORS IN RELATION TO SIDE SHOOT DEVELOPMENT IN THE TOMATO

SummaryA study has been made of the endogenous factors controlling lateral bud initiation and development in the variety Craigella, and two isogenic lines of this variety, Craigella Blind (blbl) and Craigella Lateral Suppressor (isls), in both of which side shoot growth is suppressed to varying degrees. Winter‐ and summer‐sown plants are compared.Lateral Suppressor plants contained higher endogenous levels of auxin in their apices, mature leaves and stems than did normal plants, but lower level of cytokinins in all parts except the stem, where the levels were similar in both types. The levels of abscisic acid‐like substances were consistently higher in the stems of Lateral Suppressor plants than in the corresponding tissue of normal plants, but other plant parts showed a more variable pattern. Lateral Suppressor plants contained higher levels of gibberellin than did normal plants.Blind plants contained higher levels of auxin in the apices and stem than did normal plants, but the levels in mature leaves showed no consistent pattern. Higher levels of abscisic acid‐like substances were present in the stem and axillary buds of blind plants than in normal plants, with again a more variable pattern in other plant parts. The levels of cytokinins and gibberellins varied considerably between the two sowing dates.A possible hormonal mechanism of control of axillary bud development is discussed.

Influence of Gibberellic Acid on Growth and Endogenous Auxin Level in Epicotyl and Hypocotyl Tissues of Normal and Dwarf Bean Plants

AbstractApplication of gibberellic acid to the apex of dwarf bean plants (cv. Alabaster) stimulated the elongation growth of epicotyl and hypocotyl but showed no significant effect on elongation growth in a normal cultivar (‘Blue Lake’). Gibberellin‐treatment of dwarf plants was characterized by about twofold increase in the level of endogenous auxin. Maximum increase in IAA level was observed after 48 h of GA treatment. There was less increase in IAA content in normal bean plants. — Gibberellin treatment to excised epicotyl and hypocotyl sections of either dwarf or normal cultivar showed no effect on elongation growth. However, a considerable increase in the auxin level was observed in the sections of the dwarf cultivar. The maximum effect occurred with only 1 h incubation in basal medium containing gibberellin. — The indolo‐α‐pyrone spectro‐fluoremetric method for IAA determination was used.

Endogenous Growth Regulators and Summer Tillering of Tall Fescue1

In the southern Corn Belt, tall fescue (Festuca arundinacea Schreb.) produces most of its vegetative growth during the spring and autumn. Generally little growth or new tiller initiation occurs during midsummer, even though the potential sites (buds) for tiller production are present. Failure of buds to elongate into tillers may be controlled by endogenous growth regulators. We investigated the influence of endogenous plant auxins on the elongation of buds into new tillers for tall fescue grown under field and growth chamber conditions. High temperature in the field and growth chamber (31/17 C) favored the accumulation of endogenous auxin in stem bases, and this appeared related to the inhibition of tiller initiation in early summer. Low temperature in the field and growth chamber (22/11 C) favored the accumulation of auxin in shoots and a high level of shoot auxin appeared related to active tiller development. Endogenous auxin levels in both shoots and stem bases were low in late summer.

Continuous propagation of tomato plants by means of callus cultures

Callus obtained in vitro from stem internode tissue was used to investigate the possibilities for accelerated vegetative propagation of Lycopersicum esculentum Mill. and Lycopersicum peruvianum (L). The results of different tests with phytohormones pointed to a high endogenous auxin level in the original stem explants of L. peruvianum. In L. esculentum shoots were obtained when high amounts of zeatin or coconut-milk were applied. Explants of CCC-pretreated (2 chloroethyl trimethyl-ammonium chloride) tomato plantlets showed a significant increase in shoot formation as compared to the untreated ones. Callus tissue that was more than 2 years old and had been used in 30 transfers still had the capacity to produce normal shoots and roots. More than 200 resulting plants were observed in glasshouse conditions for possible genetic variations. No striking deviations from the original phenotype occurred. Seeds harvested from the fruits of self-fertilized flowers on these plants were sown under normal growth conditions. Some plants of one particular cultivar showed signs of accentuated vegetative development.

Zur Regulation des Protonemawachstums von Athyrium filix-femina (L.) Roth

The effects of auxin (IAA) and of the antiauxin p-chlorophenoxyisobutyric acid (PCIB) on the growth of young protonemata of Athyrium filix-femina were compared under different light conditions. In blue light of high intensity cell division and elongation are promoted by specific concentrations of IAA, while in blue light of low intensity only cell elongation is increased. In red light addition of IAA leads to inhibition of cell division and elongation. Opposite effects are observed after addition of the antiauxin. In red light inhibition of cell division and elongation by high concentrations of PCIB can be relieved by addition of IAA. Under these conditions the optimal concentration of IAA is lower for cell elongation than for cell division. From these results it is assumed that in blue light the endogenous level of auxin decreases with increasing light intensity and is lower in blue than in red light. The change in differential sensitivity of cell division and elongation in red light could possibly participate in the stabilization of protonemal growth.

Effect of Ethephon (2-Chioroethyl Phosphonic Acid) on Endogenous Levels of Auxins, Inhibitors and Cytokinins in Relation to Senescence and Abscission inVicia FabaL.

SummaryTreating three cultivars of Vicia faba L. with ethephon led to reduced vegetative growth and enhanced abscission of leaves, flowers and immature pods. No clear pattern emerges of changes in the levels of endogenous auxin and inhibitors as a result of treatment with the growth regulator. Cytokinin levels in leaves of treated plants were much higher than in the controls but no changes occurred in stem tissue. The results are discussed in relation to senescence, abscission and flowering.

Studies ON ENDOGENOUS LEVELS OF ETHYLENE AND AUXIN IN VICIA FABA DURING GROWTH AND DEVELOPMENT

SUMMARYEndogenous levels of ethylene, auxins and inhibitors have been followed during the course of development in two varieties of Vicia faba having markedly different growth habits. Increases in internal ethylene levels correlate well with the time of abscission of flowers or pods. No clear correlations were observable between any particular developmental process and endogenous levels of auxin or inhibitors, although there was some correlation between inhibitor levels and abscission. The role in the control of development of the three types of growth regulator studied is discussed.

Promotion of Sucker Development on Populustremuloides Root Cuttings by an Antiauxin

Aspen (Populustremuloides Michx.) root cuttings collected in June, when endogenous auxin levels are high, were treated with α-(p-chlorophenoxy)isobutyric acid (CPIBA), an apparent antiauxin, to determine the effect on subsequent sucker development. CPIBA relieved auxin inhibition in the excised roots and thus increased the number of suckers produced on each root.