Low Concentrations Of Indoleacetic Acid Research Articles

MICROPROPAGATION STUDIES AND ANTIOXIDANT ANALYSIS OF THE ENDANGERED PLANTS OF BULGARIAN YELLOW GENTIAN (Gentiana lutea L.)

In order to develop an efficient micropropagation system, it is essential to establish the appropriate concentration of growth regulators for seed germination, shoot formation and rooting. Nodal segments from in vitro obtained seedlings of Gentiana lutea L. were cultured in vitro in Murashige and Skoog’s medium supplemented with BAP, Thidiazuron and Zeatin (0.5, 1.0 and 2.0 mg L−1). A maximum number of shoots with the highest height was recorded at 2.0 mg L−1 BAP. For further optimization of the process, we used nutrient media containing BAP and Zeatin with a combination of low concentration of Indoleacetic acid. MS medium containing 2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA resulted in maximum numbers of shoots 94.3) with shoot height 2.5 cm. The multiple plants were successfully ex vitro acclimatized with 65% survival. The presence of growth regulators (2.0 mg L−1 Zeatin and 0.2 mg L−1 IAA) in the nutrient media resulted in an effective antioxidant activity in G. Lutea determined by the low molecular antioxidant metabolites such as phenols and flavonoids and activities of antioxidant enzymes – catalase, ascorbate peroxidase, guaiacol peroxidase, and superoxide dismutase. The described protocol allows the establishment of numerous micropropaged plants of rare and endangered G. lutea.

Mass multiplication of Pogostemon cablin (Blanco) Benth genotypes and increase of essential oil and patchoulol yield

Patchouli ( Pogostemon cablin) is an aromatic species indigenous to Asia that has been cultivated in many parts of the world for the extraction of essential oils from its leaves. The objective of this study is to develop protocols for plant regeneration and acclimatization from three genotypes of patchouli. For the plant regeneration experiment, a completely randomized factorial design, employing the growth regulators kinetin and indole acetic acid (IAA), was used. The acclimatization used different mixtures of coconut coir dust and vermiculite supplemented with NPK fertilizer and limestone. Direct regeneration of plants was observed for MS medium supplemented with low concentrations (0.5–2.0 mg L −1) of kinetin and IAA alone or in combination for all of the studied genotypes. For genotypes POG014 and POG021, there were 175 and 154 shoots, respectively, obtained per explant with the use of 1.0 mg L −1 kinetin and 0.5 mg L −1 IAA. For genotype POG002, there were 41 shoots obtained per explant in a medium supplemented with 1.0 mg L −1 kinetin. The acclimatization of micropropagated plantlets of all three genotypes showed the best results with the vermiculite substrate plus MS medium salts. Essential oil content and the percentage of patchoulol were higher in plants derived from micropropagation in the three genotypes studied.

Rapid plant regeneration of chrysanthemum (Chrysanthemum morifolium L.) through shoot tip culture.

Shoot multiplication of chrysanthemum was achieved from shoot tip explant, using MS media supplemented with different concentrations and combinations of plant growth regulators. Different parameters including shoot initiation percentage, average number of shoots per explant, length of shoots (cm), number of leaves per shoot and number of nodes per shoot were studied during the course of study. Low concentration of indole-acetic acid (IAA, 0.1 mg/l) excelled all the other concentrations in almost all the parameters studied when used alone, as maximum shoot initiation (86.6%), shoot per explants (3.9), length of shoots (4.3 cm), number of leaves (10.0) and nodes (4.8) were recorded in it. Intermediate concentration of benzyladenine purine (BAP, 1.0 mg/l) is superior to all the other BAP concentrations used when used alone. MS media fortified with 1.0 mg/l BAP had produced the maximum shoot initiation (93.3%), shoot per explant (4.1), length of shoots (5.0 cm) number of leaves (11.0) and nodes (5.5). Similarly, when the combination of different concentrations of IAA and BAP were used, significant results regarding the regeneration of chrysanthemum plantlets were achieved. MS media supplemented with intermediate levels of BAP (1.0 and 2.0 mg/l) along with lower concentrations of IAA (0.1 and 0.2 mg/l) showed better results as compared to other concentrations and combinations. Satisfactory rooting response was obtained in half strength MS media supplemented with 0.2 mg/l indole butyric acid (IBA).

Effect of indole-acetic acid (IAA) on the development of symptoms caused by Pythium ultimum on tomato plants

The effect of indole-acetic acid (IAA) on the development of symptoms caused by Pythium ultimum on tomato plants was investigated using different bioassays. Application of IAA (5 μg ml−1) on tomato seedlings inoculated with P. ultimum did not affect their emergence suggesting that IAA did not affect the severity of Pythium damping-off. However, IAA was shown to influence the development of P. ultimum symptoms on tomato plantlets. Low concentrations of IAA (0–0.1 μg ml−1) within the rhizosphere of plantlets increased the severity of the symptoms caused by P. ultimum, while higher concentrations (10 μg ml−1), applied either by drenching to the growing medium or by spraying on the shoot, reduced the symptoms caused by this pathogen. In addition, the study demonstrated that P. ultimum produces IAA in liquid culture amended with L-tryptophan, tryptamine or tryptophol (200 μg ml−1) and in unamended culture.

Differential IAA dose response relations of the axr1 and axr2 mutants of Arabidopsis

In comparison to wild type Arabidopsis thaliana, the auxin resistant mutants axr1 and axr2 exhibit reduced inhibition of root elongation in response to auxins. Several auxin‐regulated physiological processes are also altered in the mutant plants. When wild‐type, axr1 and axr2 seedlings were grown in darkness on media containing indoleacetic acid (IAA), promotion of root growth was observed at low concentrations of IAA (10−11 to 10−7M) in 5‐day‐old axr2 seedlings, but not in axr1 or wild‐type seedlings. In axr1 there was little or no measurable root growth response over the same concentration range. In wild type, root growth was inhibited at concentrations greater than 10−10M and no detectable root growth response was observed at lower concentrations. In addition, production of lateral roots in response to IAA increased in axr2 seedlings and decreased in axr1 seedlings relative to wild type. Promotion of root elongation and initiation of lateral roots in axr2 seedlings in response to auxin indicate that axr2 seedlings are able to perceive and respond to IAA.

Evidence for Two Indoleacetic Acid-Induced Growth Responses in the Avena Straight-Growth Indoleacetic Acid Assay.

Floating Avena sativa L. cv Victory coleoptile segments were used to determine whether the straight-growth indoleacetic acid (IAA) assay can be reconciled with the Avena curvature assay and the Cholodny-Went theory of photo- and gravitropism. Measurements of segment length after 5 h yield sigmoid-shaped IAA dose-response curves with the growth rate leveling off at 1 [mu]M. However, measurements made at 24 h generate bell-shaped curves with maximal growth being induced by 10 [mu]M IAA. The difference between short- and long-term IAA dose-response curves is not due to IAA degradation; instead, it is the result of two growth responses to IAA. The initial one is rapid, responds to low concentrations of IAA, and lasts for 12 h. The second response is less sensitive to IAA than the first one. It appears after 6 h but is not obvious until the last 12 h of a 24-h incubation. The profile of short-term IAA dose-response curves reflects the initial growth response, whereas that of the 24-h curve is the sum of both growth responses. Linear-linear plots of 5- and 24-h dose-response curves show that coleoptile segment growth rate is proportional to IAA concentration up to 0.3 [mu]M. When the efficiency of IAA action is taken into account, it is found that the most effective IAA concentration for short and long incubations is 0.4 [mu]M. It is concluded that the Avena straight-growth IAA assay is as sensitive as the Avena coleoptile curvature assay, and that it is consistent with the Cholodny-Went theory.

Spontaneous somatic embryogenesis and plant regeneration from root cultures of Peucedanum palustre

The regeneration of Peucedanum palustre (L.) Moench (milk parsley) was established for the first time via somatic embryogenesis from primary root cultures. Callus formation occurred on the root cultures and showed spontaneous embryogenic capability on B5 basal medium supplemented with a low concentration of indoleacetic acid (5.5 × 10(-7) M). 2,4-Dichlorophenoxyacetic acid was not needed for the initiation of embryogenesis. The somatic embryos germinated and formed plantlets on hormone-free B5 medium. These plantlets were easily transferable to pots, and are presently passing their second growing season in the greenhouse.Development of the somatic embryos progressed through the globular, heart-shaped, torpedo-shaped, and cotyledonary stages, typical of zygotic embryos. Synchronization performed by sieving the embryos did not affect the development time. The culture has retained its embryogenic capacity for 25 months.

Growth of the gynophore of the peanut Arachis hypogaea. 2. Regulation of growth

It was previously shown that removal of the ovary, which occupies the distal millimetre, caused cessation of growth of the gynophore and its intercalary meristem, suggesting that the ovary was a source of growth-promoting substances. Control of growth was studied in the gynophore of the peanut Arachis hypogaea L., cv. Bukene No. 2. Low concentrations of indoleacetic acid promoted growth of decapitated gynophores, whereas high levels inhibited elongation. Gibberellic acid promoted growth of the decapitated gynophores, whereas kinetin inhibited growth at all concentrations used. A combination of indoleacetic acid and gibberellic acid promoted extension growth of the decapitated gynophores above that of the intact gynophores; this was characterized, however, by a different pattern of cell division and cell elongation from that observed in the intact gynophores. Indoleacetic acid affected the "youngest" tissues, whereas gibberellic acid affected the whole length of the growing zone. High levels of indoleacetic acid caused diageotropism of the gynophores. Application of [14C] indoleacetic acid to vertical gynophores after the ovary was excised indicated that indoleacetic acid became redistributed to one side, resulting in horizontal bending. Thus an increased amount of auxin from the enlarging ovary may be involved in placing the ovary parallel to the soil surface when it reaches a suitable depth in the soil, during normal geocarpic development. Triiodobenzoic acid reduced growth when applied in lanolin as a ring between the ovary and the meristem but not when applied proximal to the meristem, suggesting that triiodobenzoic acid prevented the transport of auxin from the ovary to the meristem.

Stomatal response of chlorocholine chloride and indole-3-acetic acid inCommelina communis L.

The apertures of stomata on isolated epidermal peels from both the leaf surfaces ofCommelina communis were reduced in response to chlorocholine chloride as the concentrations increased from 0·01–10·0 mol m−3. When chlorocholine chloride was applied in combination with different concentrations of indoleacetic acid, stomatal closure occurred only when a high concentration of chlorocholine chloride was applied with a low concentration of indoleacetic acid, while low concentrations of chlorocholine chloride did not affect the stimulation of aperture caused by indoleacetic acid treatments. Chlorocholine chloride treatments caused depletion of K+ from the guard cells while indoleacetic acid resulted in accumulation of K+.

Transmembrane ferricyanide reduction in tobacco callus cells

Transmembrane ferricyanide reduction in whole cells of normal and of transformed tobacco (Nicotiana tabacum) callus tissue was compared. It was found that low concentrations of indoleacetic acid (IAA, 0.1 μM), gibberellic acid (GA, 0.3 μM), and benzyl adenine (BA, 0.03 μM) stimulate external ferricyanide reduction in normal tobacco callus cells, but inhibit this reaction up to 67% in transformed cells when hormones are applied to cells 10 min prior to assay. Higher concentrations of these growth regulators (1 μM or greater) inhibit transmembrane ferricyanide reduction in both types of cells, with the exception of IAA, giving an initial stimulation of the rate (12%), followed by 24% inhibition after 2 min. The observed external ferricyanide reduction by whole tobacco callus cells may be explained on the basis of a transplasmalemma redox system, which may be associated with the iron metabolism of these cells.

Some Aspects of the Control of Root Growth and Georeaction: The Involvement of Indoleacetic Acid and Abscisic Acid

Apical segments of roots of Zea mays L. cv. Orla and cv. Anjou show a strong georeaction during 7 hours geostimulation. This is abolished by detipping the segments and restored by replacing the tips upon the apical cut surfaces. After exodiffusion of endogenous indoleacetic acid (IAA) the retipped segments showed a significantly lower geocurvature. Application of low concentrations of IAA to the basal cut surface of root segments from which endogenous IAA had not been allowed to exodiffuse increased the geocurvature of retipped Orla segments but decreased geocurvature of Anjou segments. At appropriate concentration basally applied IAA restored the georeaction capacity of root segments from which the endogenous auxin had exodiffused. The implications of the interaction between exogenous and endogenous IAA in the control of root georeaction are discussed with special reference to the normal role of endogenous IAA in the regulation of root georeaction and the variation in endogenous IAA content of roots of different cultivars of maize. The probability that the normal control of root growth and georeaction involves concomitant actions in the elongation zone of IAA moving preferentially in the acropetal direction and basipetally transported growth inhibitors (such as abscisic acid) produced in the cap cells is stressed.

Red Light Enhancement of the Phototropic Response of Etiolated Pea Stems

In the subapical third internode of 7-day-old etiolated pea seedlings, the magnitude of phototropic curvature in response to continuous unilateral blue illumination is increased when seedlings are pre-exposed to brief red light. The effect of red light on blue light-induced phototropism becomes manifest maximally 4 or more hours after red illumination, and closely parallels the promotive action of red light on the elongation of the subapical cells. Ethylene inhibits phototropic curvature by an inhibitory action on cell elongation without affecting the lateral transport of auxin. Pretreatment of seedlings with gibberellic acid causes increased phototropic curvature, but experiments using (14)C-gibberellic acid indicate that gibberellic acid itself is not laterally transported under phototropic stimuli. Neither red light nor gibberellic acid treatment has any promotive effect on blue light-induced lateral transport of (3)H-indoleacetic acid. Under conditions where phototropic curvature is increased by red light treatment, low concentrations of indoleacetic acid applied in lanolin paste to the apical cut end of the seedling cause an increased elongation response in subapical tissue. This could explain increased phototropic curvature caused by red light treatment.

Assessment of Herbicide-Induced Growth Inhibition of Soybean

Several herbicides and growth substances were applied singly and in combination at varying concentrations to soybean [Glycine max (L.) Merr. ‘Lee’]. This was an attempt to compare the growth inhibition obtained with that previously measured in the single-celled organism Chlorella pyrenoidosa Chick, and to investigate the plant pathways and sites by which inhibition occurs. Inhibition induced by paraquat (1,1′-dimethyl-4,4′-bipyridinium ion), and 2,4-D [(2,4-dichlorophenoxy)acetic acid] satisfactorily supported the hypothesis inherent in a kinetic analysis of such results, whereas, that induced by atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and chloramben (3-amino-2,5-dichlorobenzoic acid) did not. A probit analysis of the atrazine and chloramben results indicated variability in the type of toxicity. Soybean was considerably more susceptible to 2,4-D than Chlorella pyrenoidosa but there was little difference in the type of growth inhibition response produced. Both were equally susceptible to atrazine. High concentrations of the growth regulator IAA (indoleacetic acid) were antagonistic to the growth inhibition induced by 2,4-D, while competitive inhibition occurred at the low concentration of IAA. The 2,4-D had only a slight effect on the inhibitory effect of paraquat and antagonistically interfered with that induced by atrazine.

The Mechanism of Apical Dominance in Coleus

AbstractThe development of lateral buds in isolated stems of Coleus blumei is inhibited by low concentrations of indoleacetic acid or other auxins, just as in other plants. The inhibition can be fully reversed by kinetin, about 3 times as much kinetin as IAA being needed. However, the outgrowth of the same lateral buds on intact Coleus plants is sensitive to environmental conditions, well‐nourished plants in full daylight often showing little inhibition by applied auxin. It is shown that (a) the solvent used for IAA, (b) the light intensity and (c) the nitrogen and phosphorus nutrition, all control the sensitivity of the buds to auxin inhibition. Using water instead of lanolin, lowering the light intensity or decreasing the supply of either nitrogen or phosphorus all increase the degree of apical dominance.

Role of growth regulators in the bean hypocotyl hook opening response

The opening of the hypocotyl hook in bean seedlings is due to a rapid elongation of cells on the inner side of the hook elbow. Red light promotes hook opening by inducing this cell elongation.Opening is inhibited by low concentrations of indoleacetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), and higher concentrations of these auxins cause a closure of the hook. In darkness, opening is induced slightly by p-chlorophenoxyisobutyric acid (PCIB), whereas in red light this auxin antagonist promotes opening only when IAA is added simultaneously to inhibit opening.The amount of diffusible auxin released by the hook tissue is not affected by red illumination that is sufficient to induce maximal hook opening.Gibberellic acid (GA) promotes the hook opening. The magnitude of its effect is, however, rather small, especially in darkness. (2-Chloroethyl)-trimethylammonium chloride (CCC) and 2'-isopropyl-4'-(trimethylammonium-chloride)-5'-methylphenyl piperidine-1-carboxylate (Amo-1618) inhibit hook opening in red light, and this inhibition is completely overcome by addition of GA.Cytokinins and abscisic acid at rather high concentrations inhibit hook opening in light but produce no significant effect in darkness.Hook opening is promoted by Ca(++) and K(+), and notably by Co(++) and Ni(++).It is concluded that 1. endogenous gibberellin assists in hook opening, but light does not act by changing the gibberellin level; 2. light does not act by decreasing the endogenous auxin level; and 3. cytokinins or abscisic acid do not seem to have a special role in the response.

Effect of Protein Synthesis Inhibitors, Auxin, and Gibberellic Acid on Abscission

AbstractChloramphenicol, actinomycin D, and other inhibitors of protein synthesis promote abscission in several plant genera. Abscission is accelerated in species where an abscission layer is present, as well as in tissue where no abscission layer develops prior to abscission. The inhibitors promote abscission in species where cell division is reported to precede the separation processes as well as in tissues where no cell division is associated with the initiation of abscission. Indoleacetic acid (IAA) or auxin precursors, when applied with chloramphenicol and aclinomycin D, overcome the promotive effects of the inhibitors on abscission. These inhibitors apparently do not promote abscission through their effects on auxin precursor conversion, IAA transport, and IAA destruction in the petiole. IAA increases the incorporation of leucine‐1‐14C into a trichloroacetic acid precipitable fraction of the abscission zone under conditions where abscission is retarded. A low concentration of IAA which accelerates abscission, decreases incorporation of leucine into protein. Other promoters of abscission — chloramphenicol, d‐aspartic acid, and gibberellic acid —also decrease the incorporation of leucine into the protein of the abscission zone. The data indicate that enzymes required for the degradative processes associated with abscission are already present in the abscission zone whereas a continuous synthesis of protein is required for the retention of the leaf.

Differentiation of Bean Internode Segments in Tissue Culture with Added Indoleacetic Acid, 2,4-Dichlorophenoxyacetic Acid, and Maleic Hydrazide

1. Internode segments of snapbeans (Phaseolus vulgaris L.) were placed under sterile conditions in nutrient agar containing maleic hydrazide (MH), indoleacetic acid (IAA), or 2,4-dichlorophenoxyacetic acid (2,4-D) at concentrations of 0.1, 1.0, 10, and 100 p.p.m. 2. Cambium and phloem tissues proliferated in the control segments and produced roots without the addition of growth-affecting substances. Anatomical changes were similar in the controls and in the various treatments. 3. Low concentrations of IAA and 2,4-D limited the amount of callus but led to more roots. Low concentrations of MH stimulated both callus and root formation. MH at 1.0 p.p.m. induced ageotropic root growth. Callus and root formation were inhibited by 10 and 100 p.p.m. MH and by 2,4-D at 100 p.p.m.

A Comparison of Histological Responses of Bean Plants to Tryptophane and to Low Concentrations of Indoleacetic Acid

1. The histological responses of decapitated bean stems to five low concentrations of indoleacetic acid were studied. Of these concentrations, the two highest-0.2 and 0.02%-induced marked histological changes in the stem and resulted in the formation of a distinct tumor above the cut surface. The intermediate concentration-0.002%-resulted in only slight histological response. The two lowest-0.0002 and 0.00002%-were apparently below the threshold of effectiveness for indoleacetic acid under conditions of this experiment. These last concentrations appeared to induce no greater response than that which occurs in control material. The essential features of the histological responses are summarized in table 1. 2. The responses shown for the three effective concentrations, as well as those described by Kraus, Brown, and Hamner (7) for 3% indoleacetic acid, are essentially of the same pattern. In a stem tip treated with a high concentration, the responses at successively lower levels are similar to the responses which may be induced by treatment with lower concentrations. 3. A comparison of the patterns of response induced by indoleacetic acid and by tryptophane shows many dissimilarities. Significant differences have been described in the type of reaction, the degree of activity, and the vascularization of cortical parenchyma, endodermis, and primary phloem. The character and the degree of response in the pith and its relationship to tumor formation are like-wise dissimilar. A more detailed comparison is presented in table 1. 4. At none of the concentrations used did both the character and the rate of response to indoleacetic acid duplicate in entirety the response to tryptophane. On the basis of this histological individuality of effect, there appears to be a distinctive response attributable to tryptophane apart from any response which may result from the conversion of tryptophane to indoleacetic acid.