Aeroponics for adventitious rhizogenesis in evergreen haloxeric tree <Emphasis Type="Italic">Tamarix aphylla</Emphasis> (L.) Karst.: influence of exogenous auxins and cutting type

Tamarix aphylla (L.) Karst., a drought resistant halophyte tree, is an agroforestry species which can be used for reclamation of waterlogged saline and marginal lands. Due to very low seed viability and unsuitable conditions for seed germination, the tree is becoming rare in Indian Thar desert. Present study concerns the evaluation of aeroponics technique for vegetative propagation of T. aphylla. Effect of various exogenous auxins (indole-3-acetic acid, indole-3-butyric acid, naphthalene acetic acid) at different concentrations (0.0, 1.0, 2.0, 3.0, 5.0, 10.0 mg l^?1) was examined for induction of adventitious rooting and other morphological features. Among all three auxins tested individually, maximum rooting response (79%) was observed with IBA 2.0 mg l^?1. However, stem cuttings treated with a combination of auxins (2.0 mg l^?1 IBA and 1.0 mg l^?1 IAA) for 15 min resulted in 87% of rooting response. Among three types of stem cuttings (apical shoot, newly sprouted cuttings, mature stem cuttings), maximum rooting (~ 90%) was observed on mature stem cuttings. Number of roots and root length were significantly higher in aeroponically rooted stem cuttings as compared to stem cuttings rooted in soil conditions. Successfully rooted and sprouted plants were transferred to polybags with 95% survival rate. This is the first report on aeroponic culture of Tamarix aphylla which can be utilized in agroforestry practices, marginal land reclamation and physiological studies.     

Auxin-Mediated Ribosomal Biogenesis Regulates Vacuolar Trafficking in Arabidopsis

In plants, the mechanisms that regulate the transit of vacuolar soluble proteins containing C-terminal and N-terminal vacuolar sorting determinants (VSDs) to the vacuole are largely unknown. In a screen for Arabidopsis thaliana mutants affected in the trafficking of C-terminal VSD containing proteins, we isolated the ribosomal biogenesis mutant rpl4a characterized by its partial secretion of vacuolar targeted proteins and a plethora of developmental phenotypes derived from its aberrant auxin responses. In this study, we show that ribosomal biogenesis can be directly regulated by auxins and that the exogenous application of auxins to wild-type plants results in vacuolar trafficking defects similar to those observed in rpl4a mutants. We propose that the influence of auxin on ribosomal biogenesis acts as a regulatory mechanism for auxin-mediated developmental processes, and we demonstrate the involvement of this regulatory mechanism in the sorting of vacuolar targeted proteins in Arabidopsis.     

Interaction of indoleacetic Acid and gibberellic Acid in the short-term growth kinetics of oat stem segments

Gibberellins and auxins are the only hormones known that promote growth in oat (Avena sativa) stem segments, but when applied together, indoleacetic acid inhibits gibberellic acid-induced growth appreciably. This study shows that in addition to this inhibitory role, indoleacetic acid shortens the response time of the tissue to gibberellic acid.     

Growth Regulators and Wood Formation in Pinus silvestris

The formation of new xylem in the spring is preceded by bud development. In decapitated pine stem the formation of xylem is arrested until the outgrowth of interfascicular buds takes place. When indole-3yl-acetic acid (IAA) is applied to the cut surfaces of decapitated stems it induces the formation of a xylem ring on the whole length of 5-ycar old trees. Naphthaleneacetic acid (NAA) causes the formation of xylem; however, the width of the growth ring is several times broader at the point of application than at the base of the leader. Cis- and trans-cinnamic acids, coumarin, L-tryptophan, kinetin (Kin), benzylaminopurine (BAP) and gibberellic acid (GA) alone do not induce cambial divisions; however, GA and the cytokinins given jointly with IAA or NAA accelerated the basipetal stimulus which has been induced by the auxins, resulting in normal xylem formation. 2,3,5-Triiodobonzoic acid (TIBA) given jointly with IAA-induced formation of compression wood in the apical part of the stem and narrow diameter tracheids at the base. When carboxyl labelled IAA or NAA are applied to pine segments it is found that the basipetal movement of IAA is much quicker than that of NAA. GA and the cytokinins increase the rate of transport of both auxins, whereas TIBA arrests the bulk of auxin in the apical part of the stem.     

Effects of acifluorfen on auxin translocation in bean seedlings

The effect of 5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoic acid (acifluorfen) on the translocation of the¹⁴C-labeled auxins 2,4,5-trichlorophenoxyacetic acid (2,4,5-T-1-¹⁴C) and indole-3-acetic acid (IAA-1-¹⁴C) was determined. The auxins and acifluorfen were injected into the stem at the cotyledonary node of 9-day-old bean (Phaseolus vulgaris L. cv Tenderpod) seedlings. The plants were harvested 4 h after treatment and analyses of¹⁴C were made of various plant parts. Acifluorfen increased 2,4,5-T,-1-¹⁴C translocation out of the treated area and especially into the large primary leaves. This translocation pattern is indicative of apoplastic translocation and suggests that acifluorfen inhibited vein loading of the auxins. Acifluorfen affected auxin translocation in the dark as effectively as in the light even though the herbicidal effects of acifluorfen are known to be expressed only after light treatment.Journal article no. 4403 of the Agric. Exp. Stn., Oklahoma State Univ.     

Role of growth regulators in differentiation processes of maize (Zea mays L.) organs

The following paper deals with the character of endogenous auxins and gibberellinlike substances in the maize tassel and ear primordia during differentiation. Using bioassay the character of substances extracted from tassel primordia, internodes below the tassel, ear primordia and stem base was determined and correlated with the course of morphogenesis and differentiation. A low level of auxins and a high content of gibberellin-like substances accompanies the differentiation of terminal tassel. The differentiation of an ear is associated with an increment in auxin content while the level of gibberellin-like substances decreases. The character of growth substances in primordia remains practically unchanged in the course of further differentiation. The inhibitions appear in the plant and probably start numerous morphological reductions in the pistillate inflorescence structure or inhibit the growth of lateral primordia on the stemetc. The treatment of plants with maleic hydrazide at the beginning of tassel differentiation shifts the normal levels of endogenous regulators and brings about the transformation of tassel primordia into an ear. This transformation is accompanied by a marked rise in gibberellin-like substances, by an increment in auxins and the appearance of inhibitors.     

Growth Regulators in Populus tremula I. Distribution of Auxin and Growth Inhibitors

The content of acid ether-soluble auxins and inhibitors in vegetative tissues of aspen (Populus tremula L.) was determined with the Avena coleoptile straightgrowth assay. A growth promotor, tentativety identified as indol-3-yl-acetic acid, occurred in highest concentration in the growing stem parts. It was also detected in various parts of the roots. Large amounts of inhibitors (inhihitor β) were found in growing stem tissue and in upper mature stem parts. Considerably lower content of inhibitors was found in leaves, in the basal stem part and in the roots. Nonwoody growing roots and the wood of older root segments, especially, contained very smalt quantities of inhibitors. The elution volume of a part of the inhibitory activity on a Sephadex column was similar to that of abscisic acid.     

Hormonal Relations in the Phototropic Response IV. Light-Induced Changes of Endogenous Auxins in the Coleoptile

Beside indoleacetic acid (IAA), 3 auxins were found by chromatographic resolution of acidic fractions of Avena and Zea coleoptile tips. One of these auxins, designated P, occurred at levels of activity approaching those of IAA. The other 2 auxins, termed F and M, occurred at lower levels of activity. When the auxins of the excised coleoptile tips were isolated immediately after equilateral or unilateral irradiation with blue light at first positive energies, the ratio of IAA to the other auxins increases. This rise is the result of a decrease in P and F, and probably an increase in IAA. Light did not affect materially the total auxin content. It is suggested that P and F might be associated with the basipetal transport inequalities of IAA in phototropism.

P has been partially characterized. Its R_F on chromatograms developed in ammoniacal isopropanol is about 0.65. It is converted to IAA in vitro by heat. The ultraviolet absorption spectrum of chromatographically resolved P also suggests an indolyl complex. P is not readily transported basipetally, and the slope of its relative concentration-response curve (Avena section test) is lower than that of IAA. P does not appear to be any of the chemically characterized native auxins.

     

Mechanism of specific inhibition of phototropism by phenylacetic Acid in corn seedling

Using geotropism as a control for phototropism, compounds similar to phenylacetic acid that photoreact with flavins and/or have auxin-like activity were examined for their ability to specifically inhibit phototropism in corn seedlings using geotropism as a control. Results using indole-3-acetic acid, napthalene-1-acetic acid, naphthalene-2-acetic acid, phenylacetic acid, and β-phenylpyruvic acid suggest that such compounds will specifically inhibit phototropism primarily because of their photoreactivity with flavins and not their auxin activity. For example, strong auxins, indole-3-acetic acid and naphthalene-1-acetic acid, affected both tropic responses at all concentrations tested whereas weak auxins, phenylacetic acid and naphthalene-2-acetic acid, exhibited specific inhibition. In addition, the in vivo concentration of phenylacetic acid required to induce specificity was well below that required to stimulate coleoptile growth. Estimates of the percentage of photoreceptor pigment inactivated by phenylacetic acid (>10%) suggest that phenylacetic acid could be used to photoaffinity label the flavoprotein involved in corn seedling phototropism.     

Induction of tension wood by 2,4-dinitrophenol and auxins

Summary The effect of DNP and auxins on the development of the secondary xylem in erect stems ofAcer rubrum was studied. DNP affected the development of the secondary xylem only locally in the treated internode. Tension wood is formed in the stem below the DNP treatment site whereas above the application site the development of tracheary elements is altered. InAcer rubrum seedlings that were treated with auxin, especially at low concentrations, a thick ring of tension wood is developed in the erect stem below the treatment site. Previous suggestions that the formation of tension wood in arborescent angiosperms is a developmental response to auxin deficiency are discussed in terms of the induction of tension wood inAcer rubrum by DNP and auxins.The following abbreviations will be used TIBA (2,3,5-tri-iodobenzoic acid) - IAA (indole-3-acetic acid) - GA (gibberellic acid) - NAA (naphthaleneacetic acid) - 2,4-D (2,4-dichlorophenoxyacetic acid) - DNP (2,4-dinitrophenol) This material was included in a doctoral thesis submitted by P. R.Morey to the graduate school of Yale University, New Haven.     

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

¹⁴C-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-(2¹-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).Abbreviations ACP1.55 1-(2¹-carboxyphenyl)-3-phenylpropane-1,3-dione - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - IAA indol-3yl-acetic acid     

Influence of auxins on somatic embryogenesis and alkaloid accumulation in Leucojum aestivum callus

In vitro cultures of Leucojum aestivum are considered as an alternative for the production of galanthamine, which is used for the symptomatic treatment of Alzheimer’s disease. We studied the effects of auxins 2,4-dichlorophenoxyacetic acid (2,4-D), 4-amino-3,5,6-trichloropicolinic acid (picloram), 3,6-dichloro-o-anisic acid (dicamba) at concentrations of 25 and 50 µM on the induction of embryogenic callus and its capacity to induce somatic embryogenesis and alkaloid accumulation. The embryogenic response of the explants was from 30% for 25 µM of dicamba to 100% for picloram (for both 25 and 50 µM). 2,4-D (50 µM) stimulated greater callus proliferation and somatic embryo induction as compared to the other auxins. Polyethylene glycol (PEG) stimulated somatic embryo maturation. Callus grown on media containing 50 µM of auxins produced fewer phenolic compounds as compared with callus grown on media containing 25 µM of auxins. GC-MS analyses showed seven alkaloids in the in vivo bulbs and two to four in callus culture. Galanthamine was detected in callus cultivated with 2,4-D (25, 50 µM), picloram (25 µM), and dicamba (50 µM). Other alkaloids, trisphaeridine, tazettine, and 11-hydroxyvittatine were accumulated only in callus growing on medium with picloram (50 µM).     

The electric conductance of seedling stems and the water content of spruce and pine seedlings in the course of desiccation

The dependence of electric conductance (admittance) of the stem on seedling water content (on the relative water content related to dry matter, or on the water saturation deficit, respectively) was followed in spruce and pine seedlings. The dependence was statistically highly significant and strong:r = 0.80 when individual plants were evaluated andr = 0.97 when mean values of twenty-seedlmg sets were taken into account. Electric conductance values can be used as a substitute) for water content determinations in plant tissues under defined conditions, although tho exact interpretation, especially of absolute values of those quantities with regard to their capacity component, remains to be offered.     

Comparison of the growth promoting activities and toxicities of various auxin analogs on cells derived from wild type and a nonrooting mutant of tobacco

A naphthaleneacetic acid tolerant mutant isolated from a mutagenized culture of tobacco mesophyll protoplasts and impaired in root morphogenesis has been previously characterized by genetic analysis. To understand the biochemical basis for naphthaleneacetic acid resistance, cells derived from this mutant and from wild-type tobacco were compared for their ability to respond to various growth regulators. The growth promoting abilities and cytotoxicities of auxin analogs were different for mutant and wild-type cells. These different activities were not correlated with increased rate of conjugation or breakdown of the auxins by mutant cells. These observations, as well as previous studies on the interaction of the mutant with Agrobacterium, suggest that mutant resistance to auxins is not a result of a specific modification of the process by which auxins induce cell killing, but to a more general alteration of the cellular response to auxin. A screening of auxin-related molecules which induce cell death in wild-type cells but not mutant cells without promoting growth in either was performed. p-Bromophenyleacetic acid was found to display these characteristics.     

Vascular tissues development of citrus fruit peduncle is promoted by synthetic auxins

The application of synthetic auxins to entire trees of'Okitsu' Satsuma and 'Fortune' mandarins significantlyincreases fruit peduncle diameter. This effect is partially due to the increaseof fruit size promoted by the auxins, but is also due to a direct effect of thesynthetic auxins promoting the development of peduncle vascular tissues. Bothxylem and phloem development is affected by the auxins. This direct effect hasbeen shown by applying the auxins locally to the fruit or to the peduncle.     

Choline conjugates of auxins. I. Direct evidence for the hydrolysis of choline-auxin conjugates by pea cholinesterase

We synthesized the choline conjugates of three derivatives of phenylacetic acid, four derivatives of phenoxyacetic acid, and of naphthalene-1-acetic acid and measured the effects of these conjugates on pea (Pisum sativum L. cv. Alaska) stem segment elongation. We also synthesized the thioester analogs of six choline conjugates and measured their rates of hydrolysis by pea cholinesterase and their rates of spontaneous hydrolysis. With one exception, conjugates that stimulated growth were hydrolyzed at high rates by pea cholinesterase, while conjugates that were hydrolyzed at low rates by pea cholinesterase did not stimulate growth. The results are consistent with a model in which cholinesterase releases active auxins from these conjugates.     

Relazioni ormonali nello sviluppo dell'ovario delle orchidee II. Azione delle auxine in segmenti isolati dell'asse fiorale

Abstract

HORMONAL RELATIONS IN THE DEVELOPMENT OF ORCHID OVARY. II. — The effects of auxins on isolated parts of the flower axis. — The changes in fresh weight of segments of column, ovary and peduncle of Cymb[icaron]dium sp., treated in vitro with auxins (IAA, EtIA and NAA) indicate that these parts of the flower react promptly and independently to the three auxins tested. Expansion is very small in the ovary, and is more and more large moving towards the apex of the flower (fig. 1). The apical part of the column reacts somewhat more rapidly to auxin and tolerates higher concentration than the proximal part.

Naphtalenacetic acid proved to be the most active of the three auxins tested. This finding is in agreement with the higher efficiency of this substances as an inducer of parthe-nocarpy and its ability to induce large necroses of the column, when applied to the flower on the intact plant.

The plots of auxin activity against concentration of the auxins suggest thai the lower activity of IAA might be due to its destruction by indoleacetic acid oxidase.     

The effect of natural and synthetic auxins on the growth,metabolite content and antioxidant response of green alga Chlorella vulgaris (Trebouxiophyceae)

The effect of exogenously applied natural [indole-3-acetic acid (IAA), phenylacetic acid (PAA), indole-3-butyric acid (IBA)] and synthetic [1-naphthaleneacetic acid (NAA)] auxins on the growth and metabolism of green microalga Chlorella vulgaris was examined. Exogenous auxins acted in a concentration-dependent manner on algal growth. Phytohormones at concentration of 100 μM inhibited algal growth expressed as the number of cells. IAA and IBA displayed the highest biological activity at 0.1 μM, whereas PAA and NAA were characterized by the greatest stimulatory effect on the number of cells at 1 μM. Treatment with IAA and IBA at 0.1 μM or NAA and PAA at 1 μM increased the concentration of photosynthetic pigments, monosaccharides and soluble proteins in C. vulgaris. Moreover, all auxins stimulated enzymatic (ascorbate peroxidase, catalase, superoxide dismutase) and non-enzymatic antioxidant (ascorbate, glutathione) systems in C. vulgaris, and therefore, suppressed lipid peroxidation and hydrogen peroxide accumulation. The data supports the hypothesis that auxins play a central role in the regulation of C. vulgaris growth and metabolism and the components of cellular redox systems that are thought to have a prominent role in the regulation of auxin-dependent processes.