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The Residual Effect of Auxin on the Cell Wall.

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... One further qualification must be added on the basis that one does :387 not know in what manner the presumptive plastic property of the cell wall may be dissipated when metabolism is not acting to maintain it. Evidence presented by Cleland and Bonner (1956) suggested that the occurrence of cell wall expansion was the manner in which an increase in " plasticity " became expended. If this were the case, the above argument appears to apply without difficulty. ...
Article
A method was devised for following the growth rate of oat coleoptile cylinders with sufficient precision to measure the growth that occurred in 1 minute; the solution treating the section could be completely replaced with a different solution within 15 seconds. It was found that response of the elongation rate to changes in temperature was complete within 20 seconds, with a Q10 of about 3.5 in the temperature range 2–23°C, and that response to treatment with cyanide, or to treatment with oxygen when the tissue had been deprived of it, was completed in a few minutes. The results are interpreted as indicating that the rate of elongation is controlled directly by the rate of a metabolic reaction or reactions rather than by a physical property like steady-flow viscosity, and hence that the growth mechanism has the character of a chemorheological process as opposed to a plastic flow.The growth rate of oat coleoptile cylinders becomes promoted, after auxin is added, only after a lag of about 10–15 minutes at 23°C. This lag is not determined primarily by the rate of penetration of auxin into the tissue; it is approximately twice as long at 13°C. This is considered to indicate that the action of auxin is not directly upon the growth-controlling reaction, but affects the latter indirectly via temperature-sensitive metabolic pathways.
... For roughly 80 years a role for auxin in tissue softening has been known [41,42]. Over time and with many experiments, it became clear that auxin induces changes in cell wall pH, cell wall mechanical properties, cell wall chemistry, and cell wall synthesis [25,26,27,37,38,43,44,45,46,47,48,49,50,51]; however most of these experiments were performed on hypocotyl or coleoptile tissue. Here we demonstrate that auxin triggers changes in cell wall mechanics at the shoot apex, providing direct evidence for a long assumed link between auxin and new organ emergence. ...
Article
Full-text available
How instructive signals are translated into robust and predictable changes in growth is a central question in developmental biology. Recently, much interest has centered on the feedback between chemical instructions and mechanical changes for pattern formation in development. In plants, the patterned arrangement of aerial organs, or phyllotaxis, is instructed by the phytohormone auxin; however, it still remains to be seen how auxin is linked, at the apex, to the biochemical and mechanical changes of the cell wall required for organ outgrowth. Here, using Atomic Force Microscopy, we demonstrate that auxin reduces tissue rigidity prior to organ outgrowth in the shoot apex of Arabidopsis thaliana, and that the de-methyl-esterification of pectin is necessary for this reduction. We further show that development of functional organs produced by pectin-mediated ectopic wall softening requires auxin signaling. Lastly, we demonstrate that coordinated localization of the auxin transport protein, PIN1, is disrupted in a naked-apex produced by increasing cell wall rigidity. Our data indicates that a feedback loop between the instructive chemical auxin and cell wall mechanics may play a crucial role in phyllotactic patterning.
... These data support the hypothesis that the induced lag is caused by an increase in wall rigidity during pretreatment. The experiments of Heyn (1940) with Avena coleoptiles, which have been repeated by Cleland and Bonner (1956), showed that auxin acted on the wall when wall stiffening occurred in the absence of expansion. The failure of Cleland and Bonner to obtain auxin-induced expansion separated in time from auxin action in mannitol-pretreated tissue could have been due to the development of an induced lag period. ...
Article
Auxin caused a rapid shift in the point of incipient plasmolysis of a number: of tissues which showed auxin-induced expansion. The plasmolysis shift was not caused by dilution of the cell sap and might be due to an effect of auxin on the adhesion between cytoplasm and cell wall.
... Fig. 1) by reducing cell turgor, without at the same time affecting auxin-induced changes in cell wall plasticity, thus enabling some distinction to be made between 'growth dependent' and 'growth inducing' processes (e.g. Cleland and Bonner, 1956). The pH of the incubation medium was adjusted initially to around 5.8 with 0.01 N KOH and then continuously monitored. ...
Article
Data from pulse-chase studies on the turnover of glycosidic linkages in cell walls of maize coleoptile sections and other work on the effect of auxin or low pH on sugar release from ‘sheets’ of cells derived from the same tissue are presented. The qualitative and quantitative effects of auxin and low pH on sugar release from cell sheets are almost identical in the short term. Using a recently derived model of the maize coleoptile cell wall, a hypothesis is proposed concerning the role of auxin-induced proton release in the cleavage of glycosidic linkages in relation to growth.
Article
A method is described for measuring the cell wall mechanical properties of Avena coleoptiles in the absence of turgor stress or influences of a living protoplast. Forceextension curves obtained with a constant-rate-of-extension instrument and standard fiber-testing techniques demonstrate the permanence of cell wall loosening effects of prior indoleacetic acid (IAA) treatment of living tissue and provide evidence that these changes involve interactions between cell wall polymers. By this method various chemical and enzymatic modifications of cell walls can be evaluated in terms of altered mechanical properties. Thus, it was possible to remove over 97% of the cell nitrogen (including some hydroxyproline-containing protein) by hot methanol followed by enzymatic treatment and not change the extensibility properties of the tissue. In contrast, coleoptile mechanical properties were markedly influenced by chemical acetylation procedures or cellulase treatment.
Article
Using oat coleoptile segments the following results were obtained. Ten mg/l auxin (indole-3-acetic acid) increased the incorporation of uracil-2-14C and orthophosphate-32P into RNA fraction during a relatively short incubation period. Stimulation of 32P incorporation due to auxin was found only in the region heavier than ribosomal RNA, probably in the messenger RNA region. The stimulation of uracil-2-14C incorporation into RNA caused by auxin was not influenced by the presence of 0.3 M mannitol which prevents osmotically the water absorption of cells. It is concluded that auxin primarily stimulates the biosynthesis of RNA, possibly messenger, in oat coleoptile cells.
Article
Inhibition of hypocotyl growth by water stress and the antagonistic effect of gibberellic acid was studied in Brassica campestris L. cv. Varuna. Water stress alone inhibited increases in length and fresh weight of the hypocotyl. Increasing levels of GA applied simultaneously reversed the effect of water stress. Growth was related directly to water status and inversely to water saturation deficit. However, in severely stressed seedlings GA increased the length of hypocotyls, while fresh weight showed either no change or was even reduced. Thus a distinct ‘uncoupling’ between increases in length and water status was observed. GA appears to act partially by increasing the water status of the seedlings and partially by sustaining protein and RNA levels.
Article
The ultrastructure of the cell wall and its molecular organization were discussed. The various compounds (polysaccharides, proteins) which formed the architecture of the wall were first presented. Then the formation of the wall, in relation to the plasmalemma activity, was introduced. The wall extension has to be first related to the short-term plastic and elastic extensibility. Another factor which governs the rate of extension is the turgor pressure, and it was found that this growth rate is proportional to the pressure in excess of a critical pressure. The acid growth effect was then analysed and the role of auxin as an effector of a plasmalemma-bound ATPase hydrogen ion pump was discussed. Such a membrane pump caused the uptake of protons from the cytoplasm into the wall, where they could break the H-bounds joining the cellulose and xyloglucane. Finally, the processes controlling the wall-loosening were briefly analyzed in relation to the enzyme activity or the enzyme induction and to the RNA-protein implications.
Article
Ca2+Na+ exchange equilibria between Dowex 50 or cross-linked pectic acid as cation exchangers and external solutions with different anions have been measured. The Ca2+selectivity of the exchangers is decreased by the anions in the following order: acetate, β-indolyl acetate, citrate. Under not to acidic conditions ethylenediamine tetraacetate removes more Ca2+ from the exchanger than the other anions. S-shaped equilibrium curves are obtained with ethylenediamine tetraacetate, showing the bifunctionality of this anion towards Ca2+.
Article
Effect of 2,4-dinitrophenol, iodoacetic acid, mannitol, ribonuclease, CaCl2, phosphates, low oxygen tension, different temperatures, CCC and IAA on the coumarin-induced growth of sunflower hypocotyl sections have been investigated. Results indicate that coumarin-induced growth is auxin-like in type; nevertheless, the primary mode of coumarin action is probably quite different from that of IAA.
Article
Effects of auxin (indole-3-acetic acid), fungal -1,3-glucanase and pectin methylesterase on expansion and on cell wall extensibility, measured by the extensometer technique, of oat coleoptile segments were studied. Pretreatment with these substances for less than 30 min promoted tissue expansion remarkably. Under osmotic stress by 0.25 M mannitol, which prevented uptake of water by the cells, auxin increased DE but not DP in 30- and 60-min incubations. -1,3-Glucanase or -1,3-glucanase plus pectin methylesterase also increased only DE under the same conditions. A role of cell-wall-degrading enzymes in initiating cell expansion is therefore suggested.
Article
1. Auxin-induced wall loosening, as measured by the Instron extensometer technique, and the conversion of wall loosening into extension, as measured by cell elongation, differ in their relationship to turgor pressure (TP). Wall loosening can occur at any TP greater than zero while rapid cell extension only occurs when the TP exceeds a critical value (Pc). 2. The amount of auxin-induced increase in wall extensibility is proportional to the turgor pressure in the region between Pc and zero. In the absence of auxin, wall extensibility decreases slightly when TP exceeds Pc. 3. A reassessment of the turgor pressure of intact Avena coleoptiles has shown that it is greater than Pc. The TP of intact Avena coleoptiles is sufficient to permit turgor-driven cell elongation to occur. 4. It is proposed that wall extension involves two steps, each of which requires turgor pressure. Covalent bonds which render the wall rigid are broken only when the wall is under tension and when auxin is present in the tissue. Extension of the wall then requires that hydrogen bonding between polymers be broken by a TP in excess of Pc.
Article
Oat coleoptile segments were treated with or without 10 mM galactose in the presence or absence of 10 μM IAA and various concentrations of mannitol (pre-incubation). Auxin-induced growth was inhibited by galactose. Segments were then transferred to buffer solutions containing or not containing 10 mM galactose (post-incubation). Expansion growth due to rapid water absorption was observed. The expansion growth during the post-incubation was inhibited by galactose when galactose was applied during the post-incubation period or all through the pre- and post-incubation but was not affected by galactose when it was applied only during the pre-incubation. This result indicates that the galactose effect on the expansion growth is due to its inhibitory action during the post-incubation period. Galactose has been reported to be a specific inhibitor for cell wall synthesis. Thus, it is suggested that the expansion growth during post-incubation requires cell wall synthesis and is not just the process of passive water absorption. The primary action of auxin does not seem to require new synthesis of polysaccharides.
Article
This chapter discusses the growth of plant cell walls. In the course of cell growth, that may involves an increase in cell surface by a factor somewhere between 10 and 105, the wall grows accordingly, retaining in this process a remarkable unity, constancy, and coherence of structure. Growth involves increase in thickness as well as in area; these may increase simultaneously or successively. The tough elastic membrane characteristic of the mature cell is thus commonly its most conspicuous part, and in the aggregate such membranes form the skeletal framework of the plant. The fundamental feature of wall structure is its dual nature. Electron microscopy reveals the presence of microfibrils of indefinite length. Morphological studies of wall structure and growth refer almost wholly to the micellar or microfibrillar component of the wall which has these supramolecular features of structure. The chapter discusses the microfibrillar framework and its changes in growth, and also the nonfibrillar matrix of the wall and its role in wall extensibility.
Article
The reversible nature of the auxin-mediated loosening of the cell wall is shown by the ability of respiratory inhibitors to cause the loss of the auxin-induced increase in wall extensibility without affecting the basal extensibility of the wall. This reversibility makes it unlikely that wall loosening is mediated by enzymes, such as cellulase and beta-glucanase, which degrade polysaccharides, since their action is essentially irreversible.
Article
IT is well established that the curve depicting the extension growth of coleoptile sections as a function of indole-3-acetic acid concentration in the surrounding medium (the concentration curve) assumes the shape of an optimum curve. In the case of wheat coleoptile sections the curve ascends at a constant rate until the optimum is reached at approximately 10-5 M indole-3-acetic acid. The descent of the curve above the optimum is conditioned by the inhibiting effect of higher indole-3-acetic acid concentrations. This clear and distinct picture is found at least when an experimental period lasts 24 hr., while for shorter periods the course of the concentration curve is not so well known.
Chapter
It appears from the preceding chapters of this volume that growth under almost all circumstances is more or less intimately connected with metabolism. One experimental difficulty in studies of growth is to discern conditions directly, or more or less directly, affecting growth from those connected with metabolism not specifically essential for growth. This also holds true with regard to chemical growth factors. — Let us consider a unicellular bacterium or an alga. Its growth depends upon the external supply of different organic and inorganic compounds. According to the prevailing conditions sometimes one, sometimes another is deficient, thus becoming the chemical factor limiting growth. Together they form a heterogeneous set of chemical growth factors with varying modes of action.
Chapter
Die Synthese organischer Substanz ist ohne Zweifel einer der wichtigsten und fundamentalsten Lebensvorgänge, zu dessen Erforschung man sich wegen ihrer leichten Handhabung besonders gern niederer Pilze und Bakterien bedient hat. Viele an diesen Lebewesen gewonnene Erkenntnisse lassen sich auf höhere Organismen übertragen bzw. sind an diesen bestätigt worden. Das über die Energetik von Entwicklungsprozessen sowie über die damit zusammenhängenden Fragen der Assimilation und der Synthese von Zellsubstanz, insbesondere von Enzymen zusammengetragene Beobachtungsmaterial ist außerordentlich umfangreich. Es war daher nicht möglich, die einschlägige Literatur auch nur annähernd vollständig zu berücksichtigen. Hinweise auf einige grundlegende Arbeiten mögen daher das Eindringen in die angeschnittenen Fragen erleichtern. Darüber hinaus konnte nicht vermieden werden, auf einige mit der Entwicklung zusammenhängende Erscheinungen des Stoffwechsels, welche in anderen Beiträgen dieses Handbuches ausführlich behandelt werden, im Interesse einer möglichst geschlossenen Darstellung kurz einzugehen. Das gilt unter anderen für die Pasteursche Reaktion1, die Energiespeicherung2 und die Assimilation von Kohlenhydraten3.
Chapter
Die Entwicklung, die auf diesem Gebiet vor etwa 10 Jahren begonnen hat, bestimmt auch eindeutig die Arbeiten der letzten 3 Jahre. Es steht fest, daß beim Wachstum mit verschiedenen Gruppen von Regulatoren gerechnet werden muß; dabei ist es aber absolut nicht sicher, ob neben den Auxinen, Gibberellinen und Kininen noch andere, bis jetzt unbekannte Gruppen vorkommen. Diese Situation hat sich auch auf die Auxinforschung im engeren Sinne günstig ausgewirkt und zu Fortschritten geführt. Neben bisher unbekannten Auxinen bzw. Wuchsstoffen, die festgestellt wurden, sind auch verschiedene strittige Fragen, welche die Auxine bestimmter Objekte betreffen, geklärt worden.
Chapter
Despite extensive investigations, the mechanism of auxin-induced cell elongation remains a mystery. Yet certain facts about the progress are clear. Cell extension requires constant synthesis of RNA and protein (Key, 1969). The extension itself must consist of a continual series of extension events, each of which is composed of a biochemical modification of the wall (wall loosening) followed by a small amount of turgor-driven wall extension (Cleland, 1968).
Chapter
Zinc deficiency has been observed most extensively in the United States and Australia, but it occurs under field conditions in at least 20 different countries. Zinc deficiencies of plants are dramatic because of combinations of chlorosis, rosetting, dieback, and depressed or abnormal vegetative growth. It occurs on a variety of soils. Because zinc deficiency of plants is highly dramatic, it seems that it would have been identified long ago, but the rapid onset of the disease and the marked deterioration of affected plants were taken as evidence that the cause was not nutritional. Affected soils are usually of pH 6.0 or higher. Often they are sandy, although deficiencies have been found on fine-textured soils and on mucks and peats. Treatments with lime and phosphate fertilizers have been reported to induce zinc deficiencies in crops under some conditions. Old corral and barnyard sites often show zinc deficiencies.
Article
We have reinvestigated the ability of Avena coleoptiles to undergo auxin-induced stored growth (stored growth is defined as the ability of a cell to store up a potential for extension during periods of reduced turgor which can be converted into extra extension upon restoration of normal turgor). We could detect little or no stored growth, with either moderate (1-2 bar) or more severe (3-5 bar) reductions in turgor, and with varying periods (10-100 min) of reduced turgor. Earlier reports of a stored growth potential (e.g., Cleland and Bonner, 1956) are shown to be in error, in that the apparent growth potential is probably an artifact of the use of argon or nitrogen as an inhibitor of auxin action. The absence of stored growth reported here is not due to a direct inhibitory effect of the osmoticum itself on auxin action, since coleoptiles can extend in response to auxin even in the presence of mannitol if an external force is applied to the section to replace the normal turgor. These results show that the two components of cell-wall extension, wall loosening and wall extension, usually are inseparable. Two possible explanations are considered; the walls may be extending by the process of chemical creep, or the wall loosening may only occur when the load-bearing bonds are under tension.
Article
The enhancement by indoleacetic acid (IAA) of (36)Cl(-) uptake into Avena coleoptile sections was used to study the effects of a hormone on a membrane-controlled phenomenon. Compared to sections in phosphate buffer only, Cl(-) content of the cells increases 15 min after addition of IAA; the promotion is seen only with growth-active auxins and is saturated at 3 μM IAA. The percent enhancement by IAA is the same over a wide range of Cl(-) concentrations. The hormone effect is not observed at ice-bath temperature and is not correlated with growth or water movement into the cells. IAA does not influence the movement of Cl(-) in the section. While auxin must be present within the tissue in order to maintain the enhancement, there is no relationship between the total amount of auxin and the accelerated Cl(-) uptake that results. A polarity in the auxin effect is implied since only apical applications of IAA promote Cl(-) uptake.
Article
In vitro studies of IAA-induced cell elongation in Triticum aestivum have demonstrated that lead causes a large reduction in elongation. Inhibition of elongation can be reduced by increasing the concentration of IAA, or by the addition of calcium. The inhibitory effect appears to be linked with changes in the properties of the cell walls. Experiments are described which show that lead becomes bound strongly to certain chemical substances involved in cell wall architecture.
Article
The stems of Phaseolus vulgaris L. seedlings were immersed for 6 h in 10 and 100 ppm solutions of potassium naphthenates (KNap) and indolebutyric acid (IBA). Root initation was stimulated by 46 and 153 % over the control plants in treatments of 10 and 100 pm KNap respectively. Root initiation was stimulated by 164 and 297% over the control plants in 10 and 100 ppm IBA treatments respectively. Segments were cut from the third internodes of dark-grown seedlings of Pisum sativum L. variety Alaska and immersed in solutions of KNap and indolacetic acid (IAA). The stimulation of segment elongation (100 % over control segments) by 0.1 ppm KNap lacked statistical significance. KNap at 1.0 and 10 ppm significantly augmented the elongation of the segments (279 and 473% respectively over the control segments). IAA treatments at 0.1 and 1.0 ppm resulted in increases in segment elongation of 339 and 687% respectively over the control segments. The results presented suggest that KNap have at least two properties which are also possessed by auxins.
Article
Summary The seedling growth ofBrassica campestris var.varuna, has been studied, as affected by water-stress and gibberellin treatments. A ‘boost’ in the net GA response due to water-stress, has been observed. Thus presence of GA can overcome the water-stress effects.
Chapter
Auch der Zustand der nichtwachsenden, aber lebenden und aktiven Zelle ist, wie wir wissen, dynamisch charakterisiert, als Gleichgewichtszustand, in dem der dauernd ablaufende Stoffabbau durch eine Synthese gleichen Umfanges bilanzmäßig kompensiert ist (Rittenberg und Mitarbeiter 1939, Vickery und Mitarbeiter 1939, Hevesy und Mitarbeiter 1940, Schoenheimer 1942, MacVicar und Burris 1948, Mazia und Prescott 1955 u. a.). Überwiegen die Synthesen die abbauenden Vorgänge, so arbeitet die Zelle mit Stoffgewinn, sie wächst. Diese Art des Wachstums, die wir, soweit wir nur die Zunahme der plasmatischen Zellbestandteile ins Auge fassesn, als Plasmawachstum bezeichnen, ist die fundamentale, die gewöhnlich auch den anderen Wachstumsformen, dem Teilungswachstum und dem Streckungswachstum, vorauszugehen hat, diese auch zum Teil noch begleitet.
Article
The deposition, composition and structural organization of cell walls is reviewed, the basis for cell wall stability is discussed, and a two-step model system for plasticizing walls during tylose formation is presented. This model is based on a diurnal fluctuation in pH which conditions the cell walls, and the presence of common metabolic acids which remove calcium from the wall to permit wall extension. A metabolic basis for the plasticizing of cell walls is proposed.
Article
IT has been demonstrated1-5 that an increase in the extensibility of cell wall is involved in the growth-promoting effect of auxin. Hence it is of interest to see if gibberellin has a similar effect.
Article
The response of Avena coleoptile sections to high concentrations of auxin has been determined in the absence of all additives except sucrose. In most experiments the growth-time curves with 75 p.p.m. IAA showed two linear phases. In the first phase, which lasted for only 2–4 hours, extension was as rapid with 75 p.p.m. IAA as with 5 p.p.m. IAA. This rapid initial expansion phase was then succeeded by a second phase which persisted for at least 20 hours. During this second linear phase the growth-rate with 75 p.p.m. IAA was lower than with an auxin concentration of 5 p.p.m. In some experiments the first phase was absent and only the second phase was present. The response of sections to high concentrations of auxin was not influenced by the presence of buffers or absorbable cations. Omission of sucrose or the presence of moderate amounts of ethanol caused the resulting growth curves to be non-linear. The rate of uptake of auxin into the tissues was dependent on the auxin concentration and was constant for at least 24 hours.
Article
1. Transport of the plant growth hormone into the Avena coleoptile as well as the action of the hormone on cell elongation in the coleoptile are shown to depend upon aerobic metabolism. 2. Crystalline auxine, in contrast with impure preparations, affects neither the magnitude nor the respiratory quotient of coleoptile respiration. 3. Increasing age of the coleoptile cell decreases its rate of elongation much more than its rate of respiration. HCN or phenylurethane on the other hand decrease the two processes to the same extent, in spite of the fact that only a small portion of the energy liberated by respiration can be used in the mechanical process of growth. 4. From 2 and 3 it is concluded that processes of a respiratory nature but of relatively small magnitude form one or more integral steps in the chain of reactions by which the plant growth hormone brings about cell elongation.
Article
1. Sections of Avena coleoptiles are found to show a considerable elongation when suspended in solutions of growth substance. 2. This elongation does not take place in the absence of O(2) and is inhibited by KCN and phenylurethane. 3. The rate of respiration of sections of coleoptiles is increased by the addition of growth substance in concentrations which cause growth. High concentrations of growth substance inhibit growth and also respiration. 4. The increase in respiration is inhibited by KCN and phenylurethane in the concentrations which inhibit normal respiration. These concentrations are the same as those which inhibit growth. 5. From 2, 3, and 4, it seems possible that the increase in respiration caused by growth substance may be an essential part of its action in growth.
The physiology of growth in plant tissues cell wall loosening takes 1933 Auxin- 1956. Diortho substituted Plant Physiol
  • K V Thiimann
THIIMANN, K. V. The physiology of growth in plant tissues. Amer. Scientist 52: 589-606. cell wall loosening takes 1933. J. 1941. Proc. Koninkl. Akad. v 1931. Auxin- 1956. Diortho substituted Plant Physiol. 1951. 1954. 354
Weiteres Ver-suchmaterial zur plastischen and elastischen Dehn-barkeit der Zellmembran
  • A N J Heyn
  • Van Overbeek
HEYN, A. N. J. and VAN OVERBEEK, J. Weiteres Ver-suchmaterial zur plastischen and elastischen Dehn-barkeit der Zellmembran. Wetenschap. Amsterdam 34: 1190