Plant Growth Substances Produced by Micro-organisms of Soil and Rhizosphere

S ummary : Micro-organisms isolated from rhizospheres and rhizoplanes of wheat plants, and from root-free soil, produced growth regulating substances with the properties of gibberellins and indolyl-3-acetic acid (IAA). Substances inhibiting extensions of pea plant internodes and lettuce hypocotyls were also produced, especially by bacteria from the root region of seedlings 6 days old. Bacteria producing growth promoting substances were most abundant on roots of older plants. Seedlings grown aseptically with added gibberellic acid (GA₃) and IAA, or grown with a soil inoculum, developed similarly and differed in their morphology from those grown aseptically without additives.     

脱落调节物质对植物器官脱落的调控

器官脱落是植物生命过程中重要的生理现象.植物体内的许多激素和非激素类物质(扩展蛋白、H_2O_2、细胞壁水解酶等)都参与脱落过程的调控,而且是相互协同配合,共同发挥作用.本文综述了生长素、乙烯、脱落酸、赤霉素和茉莉酸等植物激素,以及非激素类物质扩展蛋白、H_2O_2和两种主要的细胞壁水解酶(纤维素酶和多聚半乳糖醛酸酶)在植物器官脱落过程中的调控作用,并对它们在植物器官脱落调控中的相互作用进行分析,以期为相关研究提供信息.     

Studies on Plant Growth Substances

1-Naphthoic acid derivatives substituted with chlorine, bromine, methyl or nitro groups at various positions of the ring were assayed for their activities in the pea straight-growth and the callus formation tests. Their growth activities are discussed from two points of view, i.e. the spatial structure hypothesis of Veldstra and the ortho reaction hypothesis advanced for benzoic acid derivatives proposed by Hansch and Muir. It appears that a combination of these two views are appropriate for the present authors’ results.     

Studies on Plant Growth Substances

The plant growth activities of the dihydro- and tetrahydro-1-naphthoic acids substituted with a halogen, methyl or nitro group at various positions of the aromatic ring are measured by the pea straight-growth test. The relationship between structure and activity is discussed. The results seem to conform well with the spatial structure hypothesis of Veldstra.     

Cotylenins,Leaf Growth Substances Produced by a Fungus

New biologically active substances named cotylenins A and B were isolated from the culture filtrate of a fungus, strain 501-7w. Isolation and characterization are described in detail. The chemical relationship between the cotylenins has been elucidated.     

Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.)

Azospirillum brasilense, a nitrogen-fixing bacterium found in the rhizosphere of various grass species, was investigated to establish the effect on plant growth of growth substances produced by the bacteria. Thin-layer chromatography, high-pressure liquid chromatography, and bioassay were used to separate and identify plant growth substances produced by the bacteria in liquid culture. Indole acetic acid and indole lactic acid were produced by A. brasilense from tryptophan. Indole acetic acid production increased with increasing tryptophan concentration from 1 to 100 μg/ml. Indole acetic acid concentration also increased with the age of the culture until bacteria reached the stationary phase. Shaking favored the production of indole acetic acid, especially in a medium containing nitrogen. A small but biologically significant amount of gibberellin was detected in the culture medium. Also at least three cytokinin-like substances, equivalent to about 0.001 μg of kinetin per ml, were present. The morphology of pearl millet roots changed when plants in solution culture were inoculated. The number of lateral roots was increased, and all lateral roots were densely covered with root hairs. Experiments with pure plant hormones showed that gibberellin causes increased production of lateral roots. Cytokinin stimulated root hair formation, but reduced lateral root production and elongation of the main root. Combinations of indole acetic acid, gibberellin, and kinetin produced changes in root morphology of pearl millet similar to those produced by inoculation with A. brasilense.     

Synthesis of Novel Plant Growth Inhibitors Structurally Related to Abscisic Acid

When paraffin wax is dispersed in medium as emulsion, some kinds of bacteria and yeasts readily grow on it. This paper presents a study on microbial cell production from solid paraffin. In this study a paraffin wax which contains 91% of normal paraffins ranging from C₂₅ to C₃₇ with the melting point of 62.5°C was used as a substate, but no solvent was used for the dispersion of the wax.

As a result of this study, the following have been found out. (1) Many strains of liquid normal paraffin assimilating bacteria and yeasts can assimilate paraffin wax. (2) Dried cell yields on added hydrocarbons of Corynebacterium hydrocarboclastus S-12-B2 and Candida tropicalis S-315-Y1 are 70% and 56% respectively, when they are cultured by wax emulsion of 0.6% concentration. (3) When nonion surface-active agent (Plysurf A210G) was added as an emulsifing agent, highly concentrated wax emulsion was obtained, but the growth of microorganisms on it was slower. Further investigation is needed to obtain better strains of bacteria and yeasts and also to find out optimum culture conditions.     

Studies on Plant Growth Accelerating Substances

By the aid of Chlorella grown on an agar plate a new method has been devised to detect soil microbes which produce plant growth accelerating substances. From the results of examining 3,300 soil microbes by this method, it was shown that the soil microbes could be divided into three groups according to their effect on the growth of Chlorella, that is, Chlorella growth accelerators, inhibitors and non-accelerators. By the cultivation of some green plants in the existence of some of these microbes or their culture filtrates, it was further shown that their effect on the growth of Chlorella and that of plants were in parallelism as a rule. The growth accelerating substances that are produced by soil microbes found in the present research were shown by the comparative experiment to be quite different from the substances previously known.     

Interactions in the Physiological Effects of Growth Substances on Plant Development

The interrelated effects of 3-indolylacetic acid and sodium2 : 4-dichlorophenoxyacetate on the growth and development ofLemna minor and Helianthus annuus have been investigated bymeans of multifactorial experiments, involving three to fivelevels of each compound. A clonal population of L. minor wasmaintained under constant conditions of light (550 foot-candles)and temperature (25 C.) and the growth regulators were addedto a phosphate-buffered culture solution (pH 51), which waschanged every 2 days. In the H. annuus experiments the compounds,in aqueous solution, were placed by means of a micro-pipetteon the leaves of young plants grown in a greenhouse or in theopen. Indolylacetic acid, at concentrations up to 25 p.p.m., increasesthe relative growth rate of L. minor on either a dry-weightor frond-area basis. Sodium dichlorophenoxyacetate at 0025p.p.m. has little effect on growth, but at and above concentrationsof 02 p.p.m. growth is depressed. The ratio of frond area tototal dry weight is increased by indolylacetic acid but is depressedby the phenoxyacetate. In the presence of indolylacetic acid,more particularly at the higher levels, the relative inhibitionof growth caused by sodium dichlorophenoxyacetate is reduced. When sunflowers are treated daily with indolylacetic acid (0,6, 30, 150 µg./ plant) or initially with sodium dichlorophenoxyacetate(0, 20, 100 µ.g./plant) in all possible combinations,then the relative growth rates of the treated leaves, the leavesabove the treated leaves, the first internode, and the rootsare depressed when each compound is applied alone. On the otherhand, the growth rate of the hypocotyl is increased by bothgrowth regulators, while for the second internode indolylaceticacid decreases the growth rate but the phenoxyacetate at thelower level accelerates it. The combined action of the two compoundson the different parts tends to be cumulative, save for thehypocotyl, where the effect of indolylacetic acid is dependenton the level of the phenoxyacetate. It is concluded that these results cannot be explained on theconcept of wholly additive effects. There is evidence that thecompounds can mutually interfere in their actions and it wouldseem that more than one mechanism is involved. Many of the resultscan be satisfactorily interpreted on the basis that the twocompounds act on a common system and that they compete withone another, but the results are not compatible with the postulatethat the dichlorophenoxyacetic acid directly inactivates indolylaceticacid.     

不同植物生长物质对牛角藓愈伤组织诱导的影响

相同剂量的GA3和2,4-D对牛角藓愈伤组织诱导效果明显,而6-BA、KT和NAA则抑制。光照对愈伤组织的形成有一定的促进作用。     

植物腺毛中防御物质的合成与调控及转运研究进展

植物毛状体来源于表皮细胞的延伸,是表皮细胞的特有结构。植物毛状体可分为腺毛和非腺毛,腺毛是具有分泌作用的毛状体,也是大量次生代谢产物的合成、储存以及释放的场所。植物腺毛常分泌不同类型的防御物质如萜类、氨基酸及苯丙烷类、酰基糖、脂肪类衍生物等,这些次生代谢物质能够保护植物免受生物和非生物胁迫,具有重要的防御作用。该文对近年来国内外有关植物腺毛的类型、防御物质的合成与调控等方面的研究进展进行综述,并重点对其合成途径、调控机理与转运机制的研究进展进行梳理,以期为防御物质的生物合成和遗传改良研究提供参考。     

Studies on Insect Growth Regulating Substances with Insect Cell Cultures

The sensitivity of cultured insect cells to a moulting hormone depended on their origin. Cell proliferation of cell-line C6/36, which originated from an Aedes albopictus larva, was suppressed by high concentrations of 20-hydroxyecdysone but was greatly promoted by low concentrations. Similar phenomena were observed with extracts of cedar and pine pollen. By employing the C6/36 cell-line for the screening of insect growth regulating substances, a highly active cell-growth promoting substance was found in a bovine pancreas extract. When 1 ppt of the partially purified substance was added to 2.5% fetal calf serum, the growth of cells was so greatly promoted that it was more than equal to that in the standard medium containing 10% of the serum.     

Levels of Growth Regulating Substances during Vernalization of Winter Wheat

Seeds of winter wheat (Triticum vulgare L.) cultivars Fema and Ferto, were vernalized at 3°C in the dark. Samples were taken 9, 18, 27, 36 and 45 days after the start of vernalization, and extracts were analysed for auxins, gibberellins and growth inhibiting substances. As vernalization progressed the levels of auxins and gibberellins increased whereas the levels of growth inhibitors decreased. The pattern of growth regulator changes was almost similar in both the cultivars. Vernalization seemingly controls the balance between growth promoting and growth inhibiting substances in winter wheat.     

Bacterial Alginate Produced by a Mutant of Azotobacter vinelandii

The optimum conditions in shaken flasks for production of bacterial alginate by mutant C-14 of Azotobacter vinelandii NCIB 9068 and a comparison of the properties of bacterial and algal alginates were investigated. The largest amount of bacterial alginate was obtained in about 110 h by a culture grown on optimum medium at 34°C and 170-rpm shaking speed. The viscosity of the culture broth was 18,400 cps and the alginate concentration reached 6.22 g/liter. The viscosity of the purified bacterial alginate was as high as 11,200 cps at a low concentration (0.6%). A greater than fivefold concentration of algal alginate was required to reach the same viscosity at a low shear rate. A solution of bacterial alginate was more pseudoplastic than that of algal alginate was. No significant differences were observed in other properties of bacterial and algal alginates such as gel formation with calcium ion, thermostability, and effect of temperature, pH, and sodium chloride on viscosity.     

The Growth Substances separated from Plant Extracts by Chromatography. I

For 0·per cent. sodium nitrite read 0·5 per cent. potassium ferricyanide