Ethylene production in habituated and auxin-requiring tobacco callus cultures. Does ethylene play a role in the habituation?

Ethylene production of habituated and auxin-requiring tobacco ( Nicotiana tabacum L. cv. Xanthi) callus cultures were compared. More ethylene was produced by auxinrequiring i.e. auxin-heterotrophic cultures than by habituated ones. Treatment with 2,4-dichlorophenoxyacetic acid increased the ethylene evolution of habituated cultures over the range 10⁻⁷ to 10⁻⁴ M , which suggests that the higher ethylene production of auxin-dependent callus is caused by the 2,4-D in the medium. The IAA levels depended on the age of both types of callus cultures.     

Auxin and Ethylene Regulation of Petiole Epinasty in Two Developmental Mutants of Tomato, diageotropica and Epinastic

The epinastic growth responses of petioles to auxin and ethylene were quantified in two developmental mutants of tomato (Lycopersicon esculentum Mill.). In the wild type parent line, cultivar VFN8, the epinastic response of excised petiole sections was approximately log-linear between 0.1 and 100 micromolar indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations, with a greater response to 2,4-D at any concentration. When ethylene synthesis was inhibited by aminoethoxyvinylglycine (AVG), epinasty was no longer induced by auxin, but could be restored by the addition of ethylene gas. In the auxin-insensitive mutant, diageotropica (dgt), no epinastic response to IAA was observed at IAA concentrations that effectively induced epinasty in VFN8. In the absence of added IAA, epinastic growth of dgt petioles in 1.3 microliters per liter exogenous ethylene gas was more than double that of VFN8 petioles. IAA had little additional effect in dgt, but promoted epinasty in VFN8. These results confirm that tomato petiole cells respond directly to ethylene and make it unlikely that the differential growth responsible for epinasty results from lateral auxin redistribution. The second mutant, Epinastic (Epi), exhibits constitutively epinasty, cortical swelling, and root branching symptomatic of possible alternation in auxin or ethylene regulation of growth. Only minor quantitative differences were observed between the epinastic responses to auxin and ethylene of VFN8 and Epi. However, in contrast to VFN8, when ethylene synthesis or action was inhibited in Epi, auxin still induced 40 to 50% of the epinastic response observed in the absence of inhibitors. This indicates that the target cells for epinastic growth in Epi are qualitatively different from those of VFN8, having gained the ability to grow differentially in response to auxin alone. The dgt and Epi mutants provide useful systems in which to study the genetic determination of target cell specificity for hormone action.     

Disruption of the Polar Auxin Transport System in Cotton Seedlings following Treatment with the Defoliant Thidiazuron

The effect of the defoliant thidiazuron (TDZ) on basipetal auxin transport in petiole segments isolated from cotton (Gossypium hirsutum L. cv LG102) seedlings was examined using the donor/receiver agar block technique. Treatment of intact seedlings with TDZ at concentrations of 1 micromolar or greater resulted in a dose-dependent inhibition of ¹⁴C-IAA transport in petiole segments isolated 1 or 2 days after treatment. Using 100 micromolar TDZ, the inhibition was detectable 19 hours after treatment and was complete by 27 hours. Both leaves and petiole segments exhibited a marked increase in ethylene production following treatment with TDZ at concentrations of 0.1 micromolar or greater. The involvement of ethylene in this TDZ response was evaluated by examining the effects of two inhibitors of ethylene action: silver thiosulfate, 2,5-norbornadiene. One day after treatment, both inhibitors effectively antagonized the TDZ-induced inhibition of auxin transport. Two days after TDZ treatment both inhibitors were ineffective. The decrease in IAA transport in TDZ treated tissues was associated with increased metabolism of IAA. The transport of ¹⁴C-2,4-dichlorophenoxyacetic acid was also inhibited by TDZ treatment. This inhibition was not accompanied by increased metabolism. Incorporation of TDZ into the receiver blocks had no effect on auxin transport. The ability of the phytotropin N-1-naphthylphthalamic acid to stimulate IAA uptake from a bathing medium was reduced in TDZ-treated tissues. This reduction is thought to reflect a decline in the auxin efflux system following TDZ treatment.     

Auxin Conjugation by Tobacco Mesophyll Protoplasts : Correlations between Auxin Cytotoxicity under Low Density Growth Conditions and Induction of Conjugation Processes at High Density

Auxin induction of the proliferation of Nicotiana tabacum (cv Xanthi) mesophyll protoplasts and of protoplast-derived cells was studied. The growth-promoting properties and cytotoxicities at high concentrations of IAA and naphthaleneacetic acid were strongly affected by cell density. The induction of growth by 2,4-dichlorophenoxyacetic acid and picloram was not affected by cell density. The comparison of catabolism of these [¹⁴C]-labeled auxins by protoplasts showed that IAA and naphthalene-acetic acid were rapidly accumulated and conjugated unlike 2,4-dichlorophenoxyacetic acid and picloram. The major catabolite derived from naphthaleneacetic acid was identified as naphthaleneacetyl-l-aspartate. The biosynthesis of this conjugate in protoplasts was inducible by naphthaleneacetic acid concentrations found to be cytotoxic under low density growth conditions. However, although it was taken up by cells, the conjugate was not cytotoxic at concentrations as high as 0.2 mm under low density growth conditions. The relationship between conjugation processes and auxin cytotoxicity is discussed.     

Effects of plant growth regulators on growth and morphogenesis in tissue culture of Chondracanthus chamissoi (Gigartinales,Rhodophyta)

Chondracanthus chamissoi (C. Agardh) Kützing (Gigartinales, Rhodophyta) is an edible species and commercialised for carrageenan production in Chile. Investigations on growth and development are needed to improve its cultivation; therefore, this study aims to evaluate the effects of plant growth regulators (PGRs) on its growth and morphogenesis. PGRs tested were two auxins [indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)] and one cytokinin (benzylaminopurine (BA)) in concentrations of 0.5, 5.0 and 50.0 μM. These PGRs were added to seawater enriched with half strength of von Stosch solution and were gelled with 0.6 % agar, and treatment control (without PGR addition) was conducted simultaneously. Apical and intercalary segments were used as initial explants. Each treatment was tested with six replicates of five axenic explants, and statistical analyses were performed. After culturing in a solid medium for 10 weeks to induce growth and callus formation, explants were cultured in liquid medium with the same experimental conditions for 10 weeks. Effects of auxins (IAA and 2,4-D) and the cytokinin BA on growth rates of apical segments of C. chamissoi were not significant, while low concentration of IAA stimulated the growth of intercalary segments. On the other hand, high concentrations of BA and IAA stimulated the callus formation in apical and intercalary segments, respectively. In liquid medium, PGR did not have a significant effect on growth rates of apical segments, while 2,4-D in concentrations from 0.5 to 50.0 μM stimulated growth of intercalary segments, and formation of lateral branches was stimulated by low 2,4-D in apical segments. These results suggest that PGRs have a regulatory role on callus formation and growth of specific explants of C. chamissoi. Furthermore, the formation of lateral branches stimulated by auxin could be used for seedling production under controlled conditions and could improve the micropropagation and cultivation of C. chamissoi in the Chilean coast.     

Auxin concentration/growth relationship for Avena coleoptile sections from seedlings grown in complete darkness

A biphasic auxin dose-response curve has been obtained for indole-acetic acid (IAA)-stimulated growth of subapical sections of coleoptiles from totally dark-grown oats (Avena sativa L. cv Lodi). The curve for growth at 6 h is composed of a log-linear phase and a modified bell-shaped phase separated by a plateau. The curve is log-linear from 0.003 to 0.4 micromolar IAA when sections are incubated in pH 5.9 buffer. The plateau of IAA concentration-neutral growth is seen from 0.4 to 4.0 micromolar IAA. Further increase in growth occurs from 4.0 to 10 micromolar IAA. Changing the pH of the buffer from 5.9 to 5.5 or 6.2 changes the shape of the curve, shifting the plateau to lower IAA concentration, or abolishing it, respectively. The synthetic auxin 2,4-dichlorophenoxyacetic acid also shows a biphasic dose-response curve, but the synthetic auxin 1-naphthalene acetic acid does not. The plateau is not affected by the auxin-transport inhibitor 2,3,5-triiodobenzoic acid. The plateau is eliminated by taking sections from coleoptiles grown under continuous dim red light. We advance a model to account for these results based on two modes of auxin uptake into the cell: carrier-mediated uptake and uptake via chemiosmotic diffusion.     

Enhanced plant regeneration in pearl millet (Pennisetum americanum) by ethylene inhibitors and cefotaxime

Cefotaxime, a cephalosporin antibiotic, and different ethylene inhibitors, such as silver nitrate, cobalt chloride, nickel chloride and O-acetyl salicylic acid, significantly delayed the loss of regeneration potential in embryogenic cultures of Pennisetum americanum. In the presence of these chemicals, ethylene content in the atmosphere of the culture vessel was less than that of the control. Cefotaxime, silver nitrate and O-acetyl salicyclic acid did not have any effect on callus growth based on fresh weight, while growth based on dry weight was enhanced by O-acetyl salicyclic acid.Abbreviations ASA O-acetyl salicylic acid - BA benzyladenine - CW coconut water - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - NAA -naphthaleneacetic acid - MS Murashige and Skoog     

Inhibition by Ethylene of Auxin-Promotion of Flower Bud Formation in Tobacco Explants Is Absent in Plants Transformed by Agrobacterium rhizogenes

The in vitro regeneration of flower buds was studied in pedicel explants from tobacco (Nicotiana tabacum L., cv Petit Havana) transformed with Agrobacterium rhizogenes, pRi 1855 (agropine type). At a low concentration (0.1 micromolar) of 1-naphthalene-acetic acid, pedicel strips from phenotypically aberrant plants regenerated two to three times more flower buds than explants from untransformed tobacco. Intermediate bud numbers were observed in transformants with a less extreme phenotype. The results can be explained by an increased sensitivity of the transformed explants to auxin with respect to flower bud regeneration. The effect of transformation on the auxin response is fully accounted for by the absence of a negative interaction of endogenous ethylene with 1-naphthaleneacetic acid, a phenomenon normally encountered in untransformed tissues. Three observations led to this conclusion. Application of 1 micromolar AgNO₃ to untransformed explants increased the number of flower buds to the level observed in transformed tissues but had no effect on transformed pedicel strips; exposure to 10 microliters per liter ethylene strongly reduced the response to auxin at all concentrations in untransformed explants but was almost ineffective in the transformed tissues; and endogenous ethylene synthesis occurred at the same rate in both types of explants.     

Citrus Tissue Culture : AUXINS IN RELATION TO ABSCISSION IN EXCISED PISTILS

An in vitro bioassay for chemicals that affect Citrus abscission was used to identify three inhibitors of stylar abscission in lemon pistil explants incubated on defined nutrient media. The three inhibitors (picloram, 4-chlorophenoxyacetic acid, and 3,5,6-trichloropyridine-2-oxyacetic acid) are all auxins, and the most potent of them (i.e. picloram) was found to be at least 10 times more active in the bioassay than 2,4-dichlorophenoxyacetic acid. Picloram (2 micromolar) also was shown to be effective in inhibiting stylar abscission in pistil explants from other Citrus cultivars such as mandarin, Valencia, and Washington navel oranges and grapefruit. To study the physiology of auxins active as abscission inhibitors versus inactive auxins in lemon pistils, the transport and metabolism of [1-¹⁴C]-2,4-dichlorophenoxyacetic acid was compared with that of [2-¹⁴C]indole-3-acetic acid, which is without effect in the bioassay over the range from 0.1-100 micromolar. Insignificant quantities of labeled indole-3-acetic acid and/or labeled derivatives were found to reach the presumptive zone of stylar abscission under the test conditions. Labeled 2,4-dichlorophenoxyacetic acid and/or labeled derivatives also were transported slowly through pistils, but some radioactivity could be detected in the stylar abscission zone as early as 24 hours after the start of incubation. Extensive conversion of [2-¹⁴C]indole-3-acetic acid to labeled compounds tentatively considered to be glycoside and cellulosic glucan derivatives was found with the use of solvent extraction methodology. A significantly smaller percentage of the radioactivity in pistils incubated on [1-¹⁴C]-2,4-dichlorophenoxyacetic acid was found in fractions corresponding to these derivatives. Both transport and metabolism appear to be important factors affecting the activity of auxins as abscission inhibitors in the bioassay.     

Morphogenesis in leaf,hypocotyl and root explants of Digitalis thapsi L. cultured in vitro

The effects of the auxins 2,4-D, NAA and IAA either alone or in combination with kinetin or BA were investigated to assess the morphogenetic potential of leaf, root and hypocotyl explants of Digitalis thapsi. Calluses were obtained from the three explants in basal medium without the addition of growth regulators and in leaves, the calluses formed roots. Application of 2,4-D, NAA or BA increased callus formation. The presence of NAA induced root formation and that of BA induced shoot formation via callus interphase. Indole-3-acetic acid alone only induced the generation of roots in the hypocotyl callus. Kinetin was ineffective in all the explants tested. Combinations of NAA with kinetin or BA were more effective in inducing organogenesis in leaf explants. Optimum responses were obtained in hypocotyl and root explants by using IAA in combination with BA, the highest rate of shoot regeneration being observed in hypocotyl explants.Rooting of the differentiated shoots was readily achieved in media without growth regulators. Regenerated plantlets were transferred to soil and grew with a survival rate of 70%.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid, Kin-kinetin - NAA naphthaleneacetic acid     

Induction of indoleacetic Acid synthetases in tobacco pith explants

Formation of indoleacetic acid synthetases in tobacco pith explants was determined by following the growth of tissue cultures under conditions of indole-3-acetic acid (IAA) deprivation and by measuring the enzymatic conversion of tryptophan to IAA in the cultures. The pith explants obtained from the parent plant (Nicotiana glauca) and from basal regions of the tumor-prone hybrid (N. glauca × N. langsdorffii) both show a requirement for exogenous IAA for growth initiation in culture. The parent pith requires the constant presence of added IAA for continued growth, but hybrid pith, after initial treatment with IAA, will grow without further additions. IAA synthetases are detected in the cell homogenates of hybrid pith explants cultured with either continuous or initial IAA addition. These observations indicate that IAA may induce its own production. In contrast, IAA synthetases are not found in the parent pith under comparable culture conditions. Besides IAA, nonhormonal compounds such as indole and tryptophan are also capable of stimulating growth of hybrid pith, possibly through the induction of IAA synthetases needed for IAA formation. Indole and tryptophan are, however, inactive in growth promotion of the parent pith. These results suggest that the genomic expression of IAA synthetase formation is more stringently controlled in N. glauca than in the tumorprone hybrid.     

Reciprocal Antagonism between the Herbicides, Diclofop-Methyl and 2,4-D, in Corn and Soybean Tissue Culture

The antagonistic interaction between the grass herbicide, diclofopmethyl (methyl 2-[4(2′,4′-dichlorophenoxy)phenoxy]propanoate) (DM), and 2,4-dichlorophenoxyacetic acid (2,4-D), was demonstrated in DM-resistant soybean (Glycine max [L.] Merr.) and DM-susceptible corn (Zea mays L.). 2,4-D caused root shortening and thickening, and induced callus growth in soybean and corn root tissue cultures at 1 and 10 micromolar. Normal soybean root growth was unaffected by 10 micromolar DM whereas corn root growth was inhibited completely by 1 to 10 micromolar DM. DM at 10 micromolar reversed completely the induction of callus growth by 1 micromolar 2,4-D in soybean roots. In corn, 10 micromolar 2,4-D reversed the growth inhibiting activity of 1 micromolar DM and induced callus growth. The antagonistic interaction between DM and 2,4-D was reciprocal and the activity of either compound depended upon the relative concentration of the other. 2,4-D did not antagonize or decrease the activity of DM by decreasing its uptake by root tissues or increasing the rate of its detoxication. The antagonistic interaction between DM and 2,4-D probably involves involves cellular activity associated with actively growing and proliferating cells and requires the presence of both compounds at the sensitive site.     

In vitro morphogenesis from excised leaf explants of Digitalis obscura L.

The morphogenic capacity of Digitalis obscura leaf explants cultured in vitro has been studied, noting factors promoting the differentiation of roots, buds and shoots as well as those promoting callus proliferation. Complete plant regeneration was obtained only by first culturing the leaf explants in a medium with NAA and BA to induce formation of buds, and subsequently transferring them to a medium without growth regulators to achieve the further development of shoots.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - NAA naphthaleneacetic acid     

Efficiency of indoleacetic acid,gibberellic acid and ethylene synthesized in vitro by Fusarium culmorum strains with different effects on cereal growth

Three different Fusarium culmorum strains having a pathogenic, a deleterious (deleterious rhizosphere microorganism), or a promoting (plant growth promoting fungus) effect on plant growth were studied for their ability to synthesize in vitro the phytohormones indoleacetic acid (IAA), gibberellic acid (GA), and ethylene. All the phytohormones tested were synthesized in cultures supplemented with wide concentration ranges of glucose and tryptophan or methionine (precursors of phytohormone synthesis). The amounts of these secondary metabolites synthesized by the particular strains were found to be significantly different. The non-pathogenic PGPF strain (DEMFc2) synthesized the highest amounts of IAA and GA, a fact that could be responsible for the growth-promoting properties of this strain. A pathogenic strain synthesized the highest amount of ethylene, which could be responsible for the negative effect of this strain on plant growth. F. culmorum isolates with a high capacity for IAA synthesis also have a high capacity for GA synthesis and irrespective of the growth conditions, a high positive correlation (R > 0.9) between the concentrations of synthesized IAA and GA in F. culmorum cultures was found. It is worth mentioning that the optimal conditions for the growth of F. culmorum isolates and the synthesis of the individual phytohormones differed from one another. The optimal growth conditions were 1.0% of glucose and 9.9 mM of methionine or 6.0 mM of tryptophan. The optimal conditions for ethylene synthesis were 0.5% of glucose and 6.6 mM of methionine, whereas 1.0% of glucose and 9.0 mM of tryptophan were optimal for IAA and GA synthesis.     

Ethylene production by plant cell cultures: the effect of auxins, abscisic Acid, and kinetin on ethylene production in suspension cultures of rose and ruta cells

Cell suspension cultures of Ruta graveolens (rue) and Rosa sp. produce ethylene. Both cultures grow at a high rate in hormone-free media. The rose cells are undifferentiated while the Ruta cells differentiate and form shoots after extended culture in hormone-free medium. Addition of 2,4-dichlorophenoxyacetic acid stimulated ethylene production in Ruta cells but not in rose cells. Abscisic acid (ABA) inhibited growth and ethylene production in rose, but only ethylene production in Ruta cells. Addition of kinetin reversed the inhibition by abscisic acid in the rose cells but not in the Ruta cells. The results suggested a distinct physiological difference between the two cultures. The Ruta cells responded to the growth regulators in a manner similar to whole plants.     

The Effect of Environmental Conditions on the Expression of Disease in Cultured Tissues of Brassica napus ssp. oldfera Infected with Leptosphaeria maculans

As a basis for devising an in vitro screening programme, culture conditions were optimized so that tissue cultures from two resistant cultivars of Brassica napus ssp. oleifera (Mikado, Bienvenu) and two susceptible cultivars (Lesira, Ceres) could be differentiated using a disease scoring scheme, when inoculated with Leptosphaeria maculans. Tissues inoculated included thin cell layer explants from soil-grown plants and in vitro-grown shoot cultures and callus tissue formed on such explants. The period of incubation and the incubation temperature were of importance in the development of differential disease reactions. Increasing temperature generally resulted in an increase in infection and too great an incubation period resulted in total overgrowth of the tissue. Increasing concentrations (1 × 10^?6 M-1 ×10^?4 M) of the auxins 1-naphthylacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and mdole-3-acetic acid (IAA) in the culture medium, resulted in a decrease in disease score of the thin cell layer (TCL) explants from soil-grown plants. The cytokinins examined 6-benzyl-aminopurine (BAP) and 6-4-hydroxy-3-methyl-2-enylaminopurine (zeatin), reduced the extent of infection of the TCL explants when used in combination with the auxin NAA. Medium containing NAA at a concentration of 1 × 10^?6 M in combination with BAP at a concentration of 1× 10^?6 or 1 × 10^?4 M allowed differentiation of the disease reactions of the resistant and susceptible cultivars, when the explants were incubated for 10 days at 20 °C after inoculation. Similar conditions of incubation and the addition of NAA (1 × 10^?6 M) combined with BAP (1 × 10^?6 M) to the medium also allowed the differentiation of the disease reactions on TCL explants from stems of in vitro shoot cultures of the cultivars Mikado and Lesira. Increasing concentrations of the auxin NAA and the cytokinin BAP resulted in a reduction in the mean disease score of the callus tissue produced on TCL explants from soil-grown plants, and NAA (1 × 10^?5 M) combined with BAP (1 × 10^?6 or 1 × 10^?5 M) allowed differentiation of resistance and susceptibility in callus tissues when incubated for 5 days at 20 °C. 2,4-D did not allow differentiation of the cultivars. This was in contrast to the inoculation of callus tissue attached to TCL explants of in vitro shoot cultures, where combinations of 2,4-D and BAP at concentrations of 1 × 10^?6 M allowed differentiation of the resistant and susceptible cultivars. These findings provide a basis for designing selection protocols of value in both traditional as well as in vitro breeding programmes to select lines of oilseed rape with resistance/novel resistance to L. maculans.     

Indoleacetic acid enhancement of the inhibition of Lemna growth caused by abscisic acid

Summary Indoleacetic acid substantially increased the inhibitory influence of abscisic acid on growth measured on fresh weight basis of Lemna gibba L. A similar synergistic action was obtained with indolebutyric acid while neither naphthylacetic acid nor 2,4-dichlorophenoxyacetic acid showed any synergism. The antiauxin para-chlorophenoxy-isobutyric acid did not counteract the synergistic action of IAA and ABA. The results indicate that the enhancing effect of IAA on the ABA action is not a typical auxin effect.Abbreviations ABA abscisic acid - IAA indoleacetic acid - IBA indolebutyric acid - NAA naphthylacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - PCIB para-chlorophenoxy-iso-butyric acid     

Genetic transformation ofEustoma grandiflorum byAgrobacterium tumefaciens

Callus cultures were initiated from micropropagated Artemisia absinthium plantlets on MS basal medium supplemented with different concentrations of BA, Kn, NAA, IAA and 2,4-d in combination or singly. Supplementing the medium with low doses of both BA in combination with NAA, and Kn in combination with NAA enhanced the growth rate of callus cultures. However, cultures grew slowly following the second subculture and the majority turned brown and died within the next month. Initiation of root and shoot primordia occured directly from leaf explants cultured on 1.81 M 2,4-d, while adventitious shoot formation from callus was observed occasionally when BA was added to the medium in combination with IAA. Furthermore, medium containing 2.22 M BA and 2.69 M NAA stimulated both callus growth and organogenesis on some callus cultures derived from leaves and stems of young stock material. The best results were obtained with leaf explants. Cytological analysis of root meristems revealed that all regenerants were diploid (2n=18), as expected.Abbreviations MS Murashige & Skoog's salts and vitamins (1962) - BA 6-benzyladenine - NAA alphanaphthaleneacetic acid - Kn Kinetin (6-furfurylaminopurine) - 2,4-d 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid - FW fresh weight - Bi biomass increase     

Enhancement of somatic embryogenesis frequency by gibberellic acid in fennel

The effect of GA₃ on somatic embryogenesis from petiole fragments excised from micropropagated fennel plantlets was studied. Explants were maintained for 4 weeks on an induction medium containing, 2,4-d and kinetin and were then transferred to a medium devoid of these growth regulators to allow embryo development. The addition of autoclaved or filter-sterilized GA₃ to the induction medium or to the embryo development medium increased the number of embryogenic explants. No positive effect was observed when GA₃ was added to the micropropagation medium of the mother plantlets. Gibberellic acid also counteracted the inhibiting effect of continuous light on the number of embryogenic explants. Moreover, the embryogenic frequency of petiole explants from several genotypes previously considered as poorly reacting was highly enhanced by GA₃.Abbreviations BA 6-benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ Gibberellic acid - IAA Indole-3-acetic acid - IBA Indole-3-butyric acid