Effect of dimethoate and chlorfenvinphos on plasma membrane integrity of Synechocystis sp. PCC 6803.

The organophosphorus (OP) insecticides dimethoate and chlorfenvinphos, at all selected concentrations (0-500 micromol liter-1), reduced the rate of accumulation of uranine and enhanced fluorescence quenching of 9-amino-6-chloro-2-methoxyacridine (ACMA). There was a significant nonlinear negative correlation between insecticide concentrations and uranine accumulation. The reduction in amount of uranine trapped inside the cells was greater in cultures treated with chlorfenvinphos, whereas quenching of ACMA fluorescence was found to be greater with dimethoate treatment. A marked difference between the effects of dimethoate and chlorfenvinphos on permeability changes in the plasma membrane of Synechocystis was also noted. The release of cellular organic carbon was observed at each concentration of chlorfenvinphos, whereas with dimethoate such an effect was noted at >/=200 micromol liter-1. The rate of uptake of substrates like 2-deoxyglucose and 2-aminoisobutyric acid (AIBA) was significantly (negatively) correlated with concentrations of both the insecticides. Chlorfenvinphos was more effective than dimethoate in reducing the active uptake of nonmetabolizable sugar and amino acid analogues.

Effect of dimethoate on photosynthesis and pigment fluorescence of Synechocystis sp. PCC 6803.

The organophosphorus (OP) insecticides are powerful inhibitors of esterases, and their toxic actions are commonly explained in terms of acetylcholinesterase (EC 3.1.1.7) inhibition but their phytotoxic effects remain unexplained. In this study the effects of an OP insecticide, dimethoate, on cyanobacterial photosynthesis and respiration were measured using the cyanobacterium Synechocystis sp. PCC 6803 as test organism. The insecticide caused enhancement of respiratory O2 consumption at all tested concentrations (10-300 microM) while photosynthesis was found to be significantly affected at concentrations > or = 50 microM. From fluorescence emission analysis, oxygen exchange measurement, and determination of 14CO2 incorporation, it was found that dimethoate caused inhibition of photosynthetic electron transport, resulting in increase of PS II fluorescence and reduction in photosynthetic carbon fixation. An increase of nonphotochemical quenching was caused by the insecticide through the increase in acidity of the thylakoid lumen. Furthermore, detachment of phycobilisomes (PBS) from the PS II reaction centers was observed in terms of increase in PBS fluorescence in treated cultures. This detachment is expected to be caused by membrane fluidity changes. The fluorescence enhancement of PS II was more than that of the PBS.

Tryptophan-dependent indoleacetic-acid biosynthesis from indole, demonstrated by double-labelling experiments.

(3)H-serine+(14)C-indole were administered to tips of sterily-grown pea seedlings and of non-sterile oat coleoptiles. The Try and IAA produced were extracted and purified by paper chromatography, and their (3)H/(14)C ratios were determined. The (3)H/(14)C ratio of IAA was lower than the (3)H/(14)C ratio of Try. However, the same decrease of the IAA (3)H/(14)C ratio was found when (3)H, (14)C-Try was supplied instead of (3)H-serine+(14)C-indole. This result supports the view that Try is the native IAA precursor and that no significant bypass from indole to IAA exists in the plant material used.

[Occurrence and metabolism of auxin in multicellular algae of the Baltic sea]. / Auxinvorkommen und Auxinstoffwechsel bei mehrzelligen Ostseealgen : III. Die Umsetzung von Indol-3-acetonitril und von Indol-3-essigsäure.

1. Unsterile and sterile green algae (2 species tested) and red algae (3 species) were able to hydrolize indole-3-acetonitrile (IAN) to indole-3-acetic acid (IES). Indole-3-acetamide (IAAm), detected together with IES, seemed to be an intermediate. Brown algae (3 species) incubated with IAN could produce neither IES nor IAAm. All algae oxidized IAN to indole-3-carboxaldehyde (IA) and indole-3-carboxylic acid (ICS). 2. IES destruction by living algae was mainly due to the activity of marine microorganisms. Sterile algae showed low activity; but sea-water previously incubated with unsterile algae, was active. IA and ICS, together with unidentified substances, were products of the IES-destruction. 3. All but one tested species of algae showed peroxidase activity in vivo. Enzyme preparations made of red and brown algae possessed neither peroxidase nor IES-oxidase activity, but preparations of 5 species of green algae (with one exception: Cladophora rupestris) showed peroxidase and IES-oxidase activity. IES-oxidase of these algae was active only in the presence of the cofactors Mn(++) and 2.4-dichlorophenol. Natural inhibitors of IES-oxidase were present in the enzyme preparations made of several (but not all) red and brown algae; they were absent in all green algae preparations.

[Occurrence and metabolism of auxin in multicellular algae of the Baltic Sea : I. On the occurrence of indole-3-acetic acid]. / Auxinvorkommen und Auxinstoffwechsel bei mehrzelligen Ostseealgen : I. Zum Vorkommen von Indol-3-Essigsäure.

The algae Enteromorpha prolifera, Enteromorpha compressa, Cladophora sericea, Pylaiella litoralis, Ceramium rubrum, Nemalion multifidum and Furcellaria fastigiata contain extractable auxin. After paper chromatography in different solvents, the Triticum section-test and Avena curvature-test showed that the main activity was due to IAA. This result was supported by colour tests with indole reagents after paper and thin layer chromatography.In Ceramium rubrum, Enteromorpha prolifera and Enteromorpha compressa the low IAA level was correlated with a high content of inhibitors.Only Furcellaria fastigiata contained an auxin in the nonacidic fraction. As yet an identification was unsuccessful.Alkali-hydrolysis of the algae using N NaOH liberated large amounts of auxins. Also in this case, IAA was the main auxin. With thin layer chromatography 2 or 3 other indole derivatives could be detected.

[Occurrence and metabolism of auxin in multicellular algae of the baltic sea : II. On the formation of Indoleacetic acid from tryptophan, with regard to the influence of the marine bacteria]. / Auxinvorkommen und Auxinstoffwechsel bei mehrzelligen Ostseealgen : II. Zur Entstehung von Indol-3-essigsäure aus Tryptophan, unter Berücksichtigung des Einflusses der marinen Bakterienflora.

Non-sterile and sterile algae converted tryptophan to IAA. The main activity of non-sterile algae was due to marine microorganisms. Sterile algae had a low conversion rate.Paper and thin layer chromatography of ether extracts obtained from the incubation solutions or from sterile algae revealed the presence of IAA, indole-3-aldehyde and indole-3-carboxylic acid. Indole-3-pyruvic acid seemed be present too. On the other hand, tryptamine, indole-3-acetonitrile, or indole-3-acetamide never could be detected.Therefore in algae the pathway of the IAA-formation from tryptophan seems to include a transaminase reaction furnishing indole-3-pyruvic acid.

The influence of epiphytic bacteriae on auxin metabolism.

Plants are settled by epiphytic bacteriae able to convert tryptophan to IAA. This bacterial activity is abolished by chloramphenicol and streptomycin but not by penicillin. Tryptophan conversion to IAA by plant parts or enzyme preparations is far more intensive in non-sterile conditions than in sterile ones. This is true for all investigated objects: Helianthus annuus, Phaseolus vulgaris, Pisum sativum, Triticum vulgare, Zea mays, Enteromorpha compressa, Fucus vesiculosus, Furcellaria fastigiata. From pea plants, 58 strains of IAA producing bacteriae were isolated and partly identified.While non-sterile plants (Pisum, Zea) contain considerable amounts of IAA (extraction, thin layer chromatography, biotest), hardly any traceable auxin can be extracted of sterile plants. But sterile plants re-infected with mixtures or single strains of suitable bacteriae again contain considerable amounts of extractable IAA.