Phase Change in Hedera helix L: I. GIBBERELLIN-LIKE SUBSTANCES IN THE TWO GROWTH PHASES

Gibberellin-like substances were extracted from all parts ofthe juvenile and adult growth phases of Hedera helix. A numberof extraction techniques were employed and estimatos of theamount of gibberellin-like activity present were made usingthree bioassays. Gibberellin like substances were present inapproximately equal amounts in leaves at the two growth phasesand appeared to be localized, in the main, in chloroplasts.Apical ‘buds’ of the juvenile phase were shown tocontain higher levels of gibberellin-like substances than theiradult counterparts. Roots, which under normal circumstancesare associated only with the juvenile phase, contained highlevels of extractable gibberellin-like substances.     

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.     

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.     

Changes in endogenous gibberellins in plant organs producing and utilizing photosynthates

The distribution of endogenous gibberellin-like substances in individual organs ofZea mays L., cv. CE 250, plants was investigated during the transition from the vegetative to the generative phase of development. The gradient of the content of gibberellin-like substances and photosynthetic activity in leaf segments was followed in different parts of the Jeaves, as well as the changes in the content of gibberellin-like substances in leaf segments during an exposure in the light and in the dark. The gradient of the content of endogenous gibberellin-liko substances in the leaves, in the stem and in the spike is interpreted in terms of possible relationship of these compounds to the regulation of sink — source.     

Effects of Daylength on Endogenous Gibberellins in Solanum andigena III. Gibberellin Production by the Leaves

Using an agar diffusion technique, it was found that leaves from potato plants growing under long days produced more gibberellin-like substances than did leaves from plants growing under short days. Short day plants irradiated with red light during the long dark period and harvested during the ensuing light period, contained levels of gibberellin-like substances approximating those found in long day grown plants. Red irradiation during the long dark period also resulted in an increase in gibberellin production in short day plants. Four zones of gibberellin-like activity (A, B, C, D) were separated by thin layer chromatography in extracts from potato leaves. Red light treatment reduced the levels of peak D and brought about a concomitant increase in the levels of peak A.     

Humic substances in straw compost with rock phosphate

The production of humic substances and their retention capacities for phosphorus and calcium released during composting of wheat straw with two types of low-grade rock phosphate were examined. Relative quantities of humic acids increased with increase of composting time, while fulvic acids production decreased after 30 days of composting. The addition of both Mussoorie and Hyperphos retarded humic acids production and enhanced fulvic acids production. Molasses incorporation had no effect on humic acids but increased fulvic acids production. The production of humic acids and their retention capacity for P and Ca were greater in the presence of Mussoorie phosphate than in the presence of Hyperphos, but fulvic acids formation was higher with Hyperphos. About 80–85% P and 90–95% Ca retained by the total humic substances were found in the fulvic acids fraction.     

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.     

Gibberellin-like Activity in the Developing Avocado Fruit

Gibberellin-like activity in avocado (Persea americana) fruit extracts was measured by the barley endosperm bioassay. Fruit tissues were anlyzed separately during fruit growth. The level of the activity found was very high in the endosperm and in the seed coats, but decreased in the latter during fruit growth. No measurable gibberellin-like activity was detected in the mesocarp or in the embryo. It is assumed that the seed coats are a site of production of gibberellin-like substances in the avocado fruit.     

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.     

Levels of gibberellin-like substances and their possible transport in developing dwarf and normal cultivars of pea (Pisum sativum L.)

The level of gibberellin-like substances was determined in the cotyledons and axis of developing seedlings of dwarf (Little Marvel) and normal (Tall Telephone) cultivars of pea (Pisum sativum L.). The effect of cotyledon removal with GA₃ application on growth was also examined. Greater levels of gibberellin-like substances were observed in the cotyledons of the normal cultivar than the dwarf. This was particularly evident in the cotyledons during the early stages of seedling growth. Subsequently there was a decline in GA levels in the cotyledons. This was coincidental with a rise in GA content in the axis with markedly greater levels in the normal than the dwarf cultivar. Decotyledonated dwarf and normal plants supplied with GA were much taller than the decotyledonated controls. This observation along with those of the gibberellin levels in the cotyledons and axis, provided circumstantial evidence that there may be translocation of gibberellins from the cotyledons to the axis.     

Changes in Gibberellin-Like Substances and Indole-3-Acetic Acid in Picea abies during the Period of Shoot Elongation

Grafted clones of Picea abies (L.) Karst. were used for the study. A very rapid and conspicuous rise in the content of gibberellin-like substances chromatographically similar to gibberellin A₁, and of indole-3-acetic acid, occurred during the brief period of most rapid shoot elongation. A few days later, when the shoot growth had terminated, very small amounts of both compounds could be detected. The changes in the qualitative pattern of gibberellin-like substances were consistent with a suggested interconversion pathway leading from non-polar to increasingly polar compounds     

Gibberellin-like Substances from Norway Spruce (Picea abies)

By use of methanol extraction, two different consecutive partition procedures, repeated polyvinylpyrrolidone column chromatography, silicic acid partition column chromatography and the dwarf rice, lettuce, and barley half-seed bioassays, several gibberellin-like substances were detected in elongating shoots of Picea abies (L.) Karst. No significant differences in the content of gibberellin-like substances could be detected between juvenile and mature trees. The shoot axes were found to contain fewer gibberellin-like substances than the needles.     

Hyphal growth and mycorrhiza formation by the arbuscular mycorrhizal fungus Glomus claroideum BEG 23 is stimulated by humic substances

Effects of humic substances (humic acid or fulvic soil extract) or saprophytic microorganisms (Paecilomyces lilacinus and an unidentified actinomycete) on growth of mycelium and mycorrhiza formation by Glomus claroideum BEG23 were studied in a hydroponic system. Humic substances stimulated root colonization and production of extraradical mycelium by the mycorrhizal fungus. Both humic and fulvic acids tended to decrease populations of culturable bacteria and fungi in the cultivation system, indicating a moderately antibiotic activity. The addition of saprophytic microorganisms able to use humic substances to the cultivation system further stimulated the development of the mycorrhizal fungus. However, stimulation of G. claroideum was also observed when the saprophytic microorganisms were heat-killed, suggesting that their effect was not linked to a specific action on humic substances. The results indicate that humic substances may represent a stimulatory component of the soil environment with respect to arbuscular mycorrhizal fungi.     

Responses of the toxic cyanobacterium Microcystis aeruginosa to iron and humic substances.

Iron is an essential element to marine biota. Different types of dissolved organic matter (DOM), such as humic substances have impacts on the marine coastal waters iron chemistry. The aim of the study was to examine how the presence of humic substances (both aquatic and sedimentary) may affect iron bioavailability to the bloom-forming cyanobacterium Microcystis aeruginosa Kutzing incubated on standard and modified mineral BG-11 media. The final iron concentrations in the growth media ranged from 0.1 to 100microM. The results demonstrate that both the growth rate and the concentration of chlorophyll a in cultures of M. aeruginosa are limited by insufficient (<10microM) Fe concentrations. The addition of aquatic humic substances in the presence of iron in concentrations <0.1microM increased the optical density 25-fold, and the production of chlorophyll a 15-fold as compared with the cultures exposed to iron only at the same concentration. Sedimentary humic acids in the presence of iron at a concentration of 10microM reduced the growth and production of chlorophyll a by 50% as compared to the cultures exposed to iron only at the same concentration. Possible mechanisms of humic substances - metal ion - alga interactions are discussed. It is suggested that aquatic humic substances could be of great importance in the formation of cyanobacteria blooms.     

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.     

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)     

Removal of Humic Substances from Aqueous Solution by Fungal Pellets

The removal of humic substances from aqueous solution at pH=4.8 and 6.0 and 25 °C by pure culture of Aspergillus niger has been examined. The removal of humic substances from aqueous phase was monitored by following the decrease in absorbance at 370 nm. COD and fungal growth were also measured. The initial concentration of humic and fulvic acids, pH and diameter of fungal pellets were found to be the most important parameters. The results suggested that decolorization of batch culture was a consequence of several processes. In the first 5 hours for pellets with diameter 1-3 mm and 10 hours for pellets with diameter 2-5 mm adsorption of humic substances was dominant. Afterwards, desorption of slightly bound humic substances and their degradation, as well as degradation of remaining humic substances in the solution, continued simultaneously through the period of 10 days.     

The Gibberellin-like Substances and Growth Inhibitors in Developing Strawberry Leaves

Gibberellin-like substances and inhibitors present in extractsof runner buds, and unfolding and mature leaves of strawberryhave been fractionated and compared. The runner-bud water-solubleresidue was more strongly inhibitory than that from unfoldingand mature leaves. The crude acid fraction from unfolding andmature leaves contained appreciable amounts of an inhibitor,probably abscisic acid, which was not detected in the buds.The unfolding leaves had a higher concentration of acidic gibberellin-likesubstances than either buds or mature leaves; they also containeda number of neutral gibberellin-like substances. Mature leaveshad a low concentration of gibberellin-like substances, allof which were acidic. A number of these were highly non-polartypes, not found in the buds or unfolding leaves.     

Water repellency of Casuarina windbreaks (Casuarina equisetifolia Forst.) caused by fungi in central Taiwan

The water repellent layer (WRL) in the Casuarina plantation near Taichung Harbor in central Taiwan is mainly due to the development of filamentous fungi. The hyphae of the isolated fungi and the metabolites of the TCHC-5 and TCHC-20 fungi are also significantly hydrophobic. In the soil layers, humic substances decrease the phosphorus fixation and contribute to the formation of WRL. The hydrophobic properties of humic substances are unfavorable for the nutrient cycling in this area. The water contact angles of fulvic acids and humic acids are pH-dependent. Increasing the solution pH value reduces the hydrophobic strength for fulvic acids and/or humic acids. TCHC-15 and TCHC-16 isolated fungi exude strong acidic metabolites (pH 2.7–3.0). This may result in polymerization and/or precipitation of fulvic acids and humic acids and increase the hydrophobic strength of the soil layers. Humic substances with aliphatic chains are the main components that form WRL in soils. Soil pH may be an indicator of the hydrophobic potential for organic matters.     

CHANGES IN THE CONTENT OF GIBBERELLIN-LIKE SUBSTANCES IN RIPENING SEED AND POD OF LUPINUS LUTEUS

The amount of gibberellin-like substances in seed, pod, embryoand "endosperm" of Lupinus luteus in relation to their developmentwas studied by means of the rice seedling test. The amount of gibberellin-like substances per seed increasedremarkably at the first stage of development, when the growthof seed and pod was very slow, and attained its maximum at suchan early stage as the dry weight of seed reached a value ofonly 10 per cent and that of pod 28 per cent of their respectivemaximum levels. Changes in amount of gibberellin-like substancespresent in the pod were very closely related to the changesin growth of pod. Gibberellin-like substances equivalent to0.3 µg gibberellin A₃ per seed and 0.028 µg perpod were found at the 20th day after anthesis, and no activityin mature seed and 0.09 µg per pod at the 50th day. Noactivity was found in the embryo itself at all stages, indicatingthat the gibberellin-like substances in seed occur only in the"endosperm," i.e. in the tissues that will eventually form testain fully ripened stage. (Received December 18, 1962; )