The effect of zinc on the biosynthesis of tryptophan,andol auxins and gibberellins in barley

The action of zinc on the growth of barley and the biosynthesis of indol compounds and gibberellin-like substances was investigated in a number of concentrations of zinc from doses stimulating growth to toxic doses. The seeds were soaked before sowing in solutions of zinc sulphate (5.10^?5 to 5.10^?1% Zn), and the plants cultivated for 7 days in water. Lower concentrations of zinc increased both plant growth and the biosynthesis of tryptophan and auxins. At the optimum concentration of 5.10^?3% Zn this increase in tryptophan amounted to 241% of the variant without zinc; in substances with an R_F corresponding to indolyacetic acid, the increase determined by the biological test, was 207% as against the variant without zinc. Higher concentrations of zinc inhibited growth, the tryptophan content was decreased to below that of the control without zinc and the auxin content also fell to below the control values. Zinc also influenced the content of gibberellin-like substances in the plants. At a concentration of 5.10^?3% Zn the increase in the growth activity in the gibberellic acid area of the chromatogram was 294% of the variant without zinc. At toxic concentrations of zinc, the content of gibberellin-like substances fell to below that of the controls. The finding that zinc acts simultaneously on the biosynthesis of auxins and gibberellins is also evidence for the common action of growth substances of various chemical types on plant growth.     

Radioresistance of kohlrabi (Brassica oleracea L,var.gongylodes L.) seeds in relation to the metabolism of indoles,auxins and gibberellins

Irradiation of the seeds of radioresistant kohlrabi with gamma-rays causes at doses SO to 300 kR a decrease in growth and a drop in tryptophan (Try) level in seven-day-old plants. The level of glucobrassicin (GLUBR), 3-indolylacetonitrile (IAN) and gibberellic acid (GA3) in these plants increases up to a maximum with a dose of about 150–200 kR, afterwards it decreases. We assume that the specific system of auxin synthesis inBrassicaceae plants takes an important part in the reparation processes and thus in the radioresistance of these plants as well. In contrast to the divergent systems of auxin biosynthesis in other plants which are damaged by lower doses of irradiation, the specific system of auxin formation via GLUBR synthesis, under formation of IAN intermediate, is widely not. attacked by radiation. Thus, these irradiated plants are supplied with auxins and with gibberellins too, the both hormones having a radioprotective effect.     

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.     

Regulative Systems in the Developing Citrus Fruit I. The Hormonal Balance in Orange Fruit Tissues

The regulative systems of auxins, gibberellin-like substances and their inhibitors in citrus fruit were studied. Masking caused by a high content of inhibitors was eliminated by using a refined method of solvent partition. Considerable amounts of auxins and gibberellin-like substances were detected in all stages of fruit development. The auxin system of the citrus fruit is highly complex and consists of various elements which undergo dynamic changes throughout the growth period. The identity of the auxins was studied using IAA-2-¹⁴C, and 88% of the radioactivity specifically migrated into the etheric pH 6.0 fraction. Although the prominent zones of promotion do not coincide with IAA, it can be concluded that the auxin promoters are probably not the “citrus auxin”. Abscisic acid-like inhibitors were found to accumulate in the external layers of the fruit, increasing in content as time advances.     

Production of auxins and gibberellin-like substances by mycorrhizal fungi,bacteria and actinomycetes isolated from soil and the mycorrhizosphere of pine (Pinus silvestris L.)

Summary Production of auxins and gibberellin-like substances by mycorrhizal fungi, bacteria and actinomycetes isolated from the mycorrhizosphere of Scots pine was studied. Chromatography and biossays were used.Most of the organisms required tryptophan for auxins production. The highest biological activity exhibited substances located at R_f 0.2–0.4.The organisms produced minute amounts of gibberellin-like substances which appeared at different R_f values. It was stated that auxins production is much more common among the root zone organisms of pine than the production of gibberellin-like substances.This research was carried out under problem MR.II.16 coordinated by the Institute of Dendrology, Polish Academy of Sciences.     

Variations in Endogenous Gibberellins in Developing Bean Seeds II. Changes Induced in Acidic and Neutral Fractions by GA(1)

Immature (8-mm), medium mature (11-mm), and mature green (16- and 17-mm) bean seeds (Phaseolus vulgaris L. cv. Kentucky Wonder and Bountiful) were incubated in gibberellin A₁ solutions for 24 hours at 20°. Extracts from the seeds were separated into nonacidic, acidic ethyl acetate, and acidic butanol fractions. These were chromatographed. The eluates of the chromatograms were tested on Progress No. 9 dwarf peas grown under red light. The level of neutral gibberellin-like substances remained unchanged in immature seed, but they increased markedly in mature green seeds. Coincident with increased levels of the neutral substances, there were significant decreases in acidic ethyl acetate-soluble gibberellin-like substances, including applied GA₁, and in 1 acidic butanol-soluble gibberellin-like substance. Seed incubation in GA₁ brought about increased activity of substance B-II in immature and medium mature seeds. The level of butanol-soluble gibberellin-like substance B-I in seeds of any size was not affected by incubation in GA₁. Considering the marked increases in activity induced in the neutral fraction and the decreases in activity of certain eluates from the chromatograms of the acidic fractions, it was concluded that the neutral fraction may serve as a reserve form of gibberellins in the dry seed. The acidic ethyl acetate substances and substance B-II may be required for normal development of the bean seed.     

Reduction of the Gibberellin Content of Pharbitis Seeds by CCC and After-Effects in the Progeny

Plants of Pharbitis nil were treated with the growth retardant (2-chloroethyl) trimethylammonium chloride (CCC) shortly before and after anthesis. Fresh and dry weight of immature seeds were not affected by the CCC treatment.

The level of gibberellin-like activity in Pharbitis seeds as compared to control seeds was strongly reduced by CCC application. The progenies of the treated plants also had a much reduced GA content in the seedling stage. These results are interpreted to indicate that CCC blocks gibberellin biosynthesis in higher plants, as it does in the fungus Fusarium.

CCC applied via the roots accumulated in the immature seeds and was carried over to the following generation. Consequently, growth of CCC progenies was dwarfed and flower formation inhibited. Both phenomena were overcome by application of gibberellin A₃.

Three gibberellin-like substances (called fractions I, II, and III) were present in Pharbitis seeds and could be separated by thin-layer chromatography. All 3 fractions were also present in seeds treated with CCC. Fractions II and III were present in much higher quantities than fraction I. Both fractions II and III promoted growth of d5 corn but only fraction II was active in dwarf peas grown under red light.

     

Gibberellin Relationships in Zinc-Deficient Plants

The content of gibberellin-like substances was reduced to aboutone seventh in maize and one half in barley and oat plants grownunder zinc-deficient conditions compared with control plantsgrown with sufficient zinc nutrition. The supplement of zincto zinc-deficient maize plants not only recovered their growthbut also increased contents of gibberellin-like substances.The growth cessation in zinc-deficient plants is discussed inrelation to the endogenous contents of gibberellin. (Received March 12, 1986; Accepted May 28, 1986)     

The effect of carbon and nitrogen sources on auxins and gibberellin-like substances synthesis by bacteria isolated from the roots of pine seedlings (Pinus silvestris L)

It was found that in the presence of sodium succinate synthesis of auxins and gibberellin-like substances by microflora in the rhizosphere of pine seedlings was higher than in the presence of the other carbon sources. The smallest amounts of these substances were found in media with sodium pyruvate. The highest C-content (C:N = 60:1) was not optimal for the synthesis of plant growth regulators. Ammonia ions inhibited the production of gibberellin-like substances. The effect of different nitrogen sources and C:N ratio on the synthesis of auxins was different depending on bacterial strain used.     

Production of auxins by bacteria isolated from the roots of pine seedlings (Pinus silvestris L.).

Qualitative and quantitative studies were carried out on the production of auxins by Coryneform bacteria, the only bacterial types isolated from roots of pine seedlings. Almost all isolates were capable of producing auxins in tryptophan containing media. In media without this amino acid only trace or no auxins were produced. Most of the bacteria studied synthesized auxins located on the chromatograms run with isopropanol, ammonia, water (10:1:1 v/v) at Rf 0.3--0.5. Moreover substances with Rf values 0.05--0.2 and 0.8--1.0 were produced by some strains. No plant growth inhibitors detected with the Avena coleoptiles biotest were produced by the bacteria studied.     

The Gibberellins of Developing Bean Seeds

Properties of gibberellin-like substances extracted from Frenchbean seeds during their development were studied. Two zonesof gibberellin-like activity were detected on paper chromatograms. Changes in activity of one of the zones correlated with changesin growth-rate of the seed. From considerations of Rf on paperchromatograms, and differential activity on dwarf peas, dwarf-1and dwarf-5 corn, it was deduced that activity of this zonewas due to substances resembling gibberellin A₁ and gibberellinA₅. Gibberellin A₅-like activity was highest in young seedsand disappeared after cell division in the cotyledons had ceased.Gibberellin A₁-like activity rose to its highest level duringthe period of rapid cell expansion in the cotyledons, afterthe disappearance of gibberellin A₅-like activity. The second zone of gibberellin-like activity was due mainlyto a non-acidic substance, which disappeared at the time GAj-likeactivity was rising to its highest level. A non-acidic substance that stimulated lateral bud growth ofdwarf peas also was detected in the extracts. It is presumedto be a cytokinin.     

L-Tryptophan-dependent biosynthesis of indole-3-acetic acid (IAA) improves plant growth and colonization of maize by <Emphasis Type="BoldItalic">Burkholderia phytofirmans</Emphasis> PsJN

Burkholderia phytofirmans PsJN is a well-known plant growth-promoting bacterium that establishes rhizospheric and endophytic colonization in different plants. PsJN inoculation promotes growth of different horticultural crops. L-Tryptophan (L-TRP) application may further improve its effectiveness, due to substrate (L-TRP)-dependent inoculum (PsJN)-derived auxins in the rhizosphere. In the present study, the substrate (L-TRP)-dependent response of PsJN inoculation to maize growth and auxin biosynthesis was evaluated under pot conditions. In vitro auxin biosynthesis by PsJN was determined in the absence and presence of L-TRP, a physiological precursor of auxins. Surface-disinfected seeds were treated with peat-based inoculum and L-TRP solutions (10^?4 and 10^?5 M). Results revealed that L-TRP application and PsJN inoculation, when applied separately, significantly increased the growth parameters of maize compared to untreated control. However, PsJN inoculation supplemented with L-TRP (10^?5 M) gave the most promising results and significantly increased plant height, photosynthesis, chlorophyll content, root biomass and shoot biomass up to 18, 16, 45, 62 and 55 %, respectively, compared to the uninoculated control. Similarly, higher values of N, P and IAA content were observed with precursor (L-TRP)–inoculum (PsJN) interaction. The inoculant strain efficiently colonized maize seedlings and was recovered from the rhizosphere, root and shoot of plants. The results imply that substrate (L-TRP)-derived IAA biosynthesis in the rhizosphere by PsJN inoculation could be a useful approach for improving the growth, photosynthesis and nutrient content of maize plants.     

Synthesis of auxins by fungi isolated from the roots of pine seedings (Pinus silvestris L.) and from soil.

Synthesis of auxins by fungi grown with and without tryptophan has been studied. 26 out of 30 fungal strains produced detectable amounts of auxins in tryptophan contain media. 18 strains produced but very small amounts of auxins in media without this amino acid. By means of paper chromatography, chromogenic reagents and biotest three active substances could be distinguished. They were found on the chromatograms run with isopropanol, ammonia, water (10:1:1 v/v) at Rf 0.05--0.2, 0.3--0.5 and 0.8--1.0. Most strains produced active substances with Rf 0.3--0.5.     

Gibberellin-like substances and indole type auxins in developing grains of normal- and high-lysine genotypes of barley

Changes in gibberellin-like activity and content of indole type auxins were investigated during grain development of the two high-lysine barley (Hordeum vulgare L.) genotypes Sv 73608 and Risø 1508, and their corresponding normal cultivars Mona and Bomi. A peak in gibberellin-like activity was found in developing grains of the normal cultivars about 18 days after anthesis, whereas the grains of the high-lysine genotypes showed a two to five times higher maximum about 3–4 days later. The auxin content of the cultivar Bomi showed a maximum between the 22nd and the 29th day after anthesis, whereas, throughout their development the grains of the mutant Risø 1508 exhibited only about ¹/10 of the maximum level of auxin found in the grains of Bomi. The normal cultivar Mona also displayed higher contents of auxin than the high-lysine genotypes Sv 73608, particularly at the later stages of grain growth, but the differences in concentration were considerable smaller than for the pair ‘Bomi’—‘Risø 1508’. It is suggested that auxins play an important role in the development of barley grains.     

The role of endogenous gibberellin-like substances and inhibitors in the growth of pea internodes

Third internodes or whole stems of 7-days old etiolated pea plants were extracted and the content of gibberellin-like substances and inhibitors has been determined. Extracts were found to contain four or five different gibberellin-like substances, some of which are chromatographically similar to GA₃. The content of gibberellins has been high in young internodes and decreased along with the internodes elongation. Brief red light irradiation brings about quantitative changes in gibberellin content, depending also on the length of internodes. The extracts contain acidic and neutral inhibitors which interfere with the response to GA₃. The content of the inhibitors does not seem to be affected by the ageing of internodes or by the light treatment.     

Indole auxins in spinach plants grown in long and short days

The endogenous auxin-like substances were analyzed in the shoot extracts of young spinach seedlings, exposed to photoperiodic induction. At least eight indole auxins were found. One of them was identified as tryptophan, the other one is most probably IAA. The plants grown in long days had a higher level of ether soluble auxins than the controls in short days. Separate extractions of plants after each of the eight inductive days showed that the auxin content was not constant, but subjected to irregular oscillations. However, parallel oscillations were also found in control plants grown in short days. Staminate plants were found to contain more endogenous auxins than the pistillate ones. It is concluded that the quantitative changes in auxins during the photoperiodic induction are probably not related to flowering, but to some other growth process, common to all plants in that phase of growth. The higher level of auxins in staminate plants may be the cause of their faster elongation before the onset of flowering.     

Production of gibberellin-like substance in the embryo of barley during germination

Summary Embryos were excised from barley seeds, their homogenates were incubated with ficin, and their content in gibberellin-like substance was assayed by means of -amylase-producing activity, but no gibberellin-like substance could be detected.Embryos free from endosperm which were cultured for five days produced measurable amounts of gibberellin-like substance. This substance was not produced when a carbon source was absent from the medium, or when air was removed after 2 days of aerobic culture. CCC and Phosfon D (at the concentration of 2×10^-4 M and 0.8×10^-4 M, respectively) inhibited the formation of the gibberellin-like substance in cultured embryos without affecting their growth.Mevalonic acid could be used as a carbon source in the culture of the embryos. The formation of the gibberellin-like substance was in this case inhibited by 0.8×10^-4 M Phosfon D, but was not inhibited by 2×10^-3 M CCC.     

The diffusion of gibberellins into agar and water during early germination of Pharbitis nil Choisy

Agar diffusion of imbibed seeds yielded significant amounts of diffusible Gibberellin-like substances. An analysis of the extractable and diffusible gibberellin-like substance, including an analysis of the remaining imbibition water of the seeds, indicated that a significant part of these gibberellin-like substances could be attributed to a net biosynthesis of these substances in the imbibing seeds. At the same time it was found that water diffusion yielded considerably more gibberellin-like activities than comparable agar diffusions i.e. 10 to 12 fold in general.Agar as well as water diffusion showed a temperature effect with regard to the yield of gibberellin-like substances particularly during the first 6 h of diffusion. The yield of these substances is lower at 10°C, and remains lower as shown with consecutive diffusions, in comparison with the yields at 20°C or 30°C.With both agar and water diffusion the sum of activities obtained with consecutive diffusions is always higher, often considerably higher, than equal periods of continuous diffusion which is probably due to inactivation and/or interference of inhibitory substances with the bioassay responses. Finally, water diffusates of both seeds and seedlings of the normal growing cv. Violet of Japanese morning glory contained considerably more gibberellin-like activities than those of the dwarf cv. Kidachi which indicated that normals synthesize more gibberellins than dwarfs.     

Auxin production by the Klebsiella planticola strain TSKhA-91 and its effect on development of cucumber (Cucumis sativus L.) seeds

Capacity of Klebsiella planticola strain TSKhA-91 for synthesis of indole-3-acetic acid (IAA) and other auxins was studied. The qualitative and quantitative composition of these compounds depends on the presence of exogenous tryptophan and on the nitrogen source. The highest IAA yield was obtained at the stationary phase of growth. Addition of L-tryptophan to the medium resulted in a significant increase (up to 85.5 μg/mL) of auxin biosynthesis, especially in the presence of nitrates. Thin-layer chromatography revealed that the indole-3-acetamide pathway was not active in this strain. The biological activity of auxins was confirmed by assay with kidney bean cuttings; the height of root formation and root number increased 16- and 6-fold, respectively. Under conditions of low-temperature stress, protective effect of K. planticola TSKhA-91 on development of cucumber (Cucumis sativus L.) seeds and stimulation of germination and root formation by its seeds were shown.     

The effect of culture medium composition and incubation time on synthesis of gibberellin-like substances by bacteria isolated from the roots of pine seedlings (Pinus silvestris L.)

It was found that synthesis of gibberellin-like substances by ten strains of Coryneform bacteria isolated from the roots of pine seedlings depended on both the composition of the medium and incubation time. More of these substances were produced in mineral medium with glucose in complex medium with casamino acids and yeast extract. Most gibberellin-like substances were found in 7 or 14-day old cultures. Culture supernatant fluids of most of the bacteria tested contained several gibberellin-like substances which on chromatograms run with the solvent system benzene, acetic acid (10:3, v/v) were located at Rf 0.0-0.3; 0.4-0.6 and 0.8-1.0.