The effect of microorganisms on phytotoxicity of herbicides. III. Interaction of Bacillus sp. 72 with Venzar.

Interactions between Venzar and some metabolites of Bacillus ps. 72 were studied. This strain was found to produce flavonoids increasing the phytotoxicity of Venzar. Venzar action was also increased by NH4+ ions released aboundantly by the bacterial strain.     

The influence of some herbicides on selected groups of microorganisms in loess and sandy soils. II. The effect of nitrification.

Studies on the effect of herbicides on nitrification in field and laboratory conditions have shown that steady use of these substances in the same field does not exert a significant effect on this process in the soil. The herbicides caused only shortlasting disturbances. Nitrification usually returned to a relative equilibrium in several days after the herbicide application.     

The effect of soil warming on bulk soil vs. rhizosphere respiration

There has been considerable debate on whether root/rhizosphere respiration or bulk soil respiration is more sensitive to long-term temperature changes. We investigated the response of belowground respiration to soil warming by 3 °C above ambient in bare soil plots and plots planted with wheat and maize. Initially, belowground respiration responded more to the soil warming in bare soil plots than in planted plots. However, as the growing season progressed, a greater soil-warming response developed in the planted plots as the contribution of root/rhizosphere respiration to belowground respiration declined. A negative correlation was observed between the contribution of root/rhizosphere respiration to total belowground respiration and the magnitude of the soil-warming response indicating that bulk soil respiration is more temperature sensitive than root/rhizosphere respiration. The dependence of root/rhizosphere respiration on substrate provision from photosynthesis is the most probable explanation for the observed lower temperature sensitivity of root/rhizosphere respiration. At harvest in late September, final crop biomass did not differ between the two soil temperature treatments in either the maize or wheat plots. Postharvest, flux measurements during the winter months indicated that the response of belowground respiration to the soil-warming treatment increased in magnitude (response equated to a Q ₁₀ value of 5.7 compared with ∼2.3 during the growing season). However, it appeared that this response was partly caused by a strong indirect effect of soil warming. When measurements were made at a common temperature, belowground respiration remained higher in the warmed subplots suggesting soil warming had maintained a more active microbial community through the winter months. It is proposed that any changes in winter temperatures, resulting from global warming, could alter the sink strength of terrestrial ecosystems considerably.     

The effect of temperature on soil respiration

лсследедовались кривые респирации образцов разцов почвы и компоста при температурах от 8 до 48о С. В пределах 8-28х С повышение температуры проявляется только ускорением процессов, характеризуемых коз??ициентом Q₁₀ 1,6 2,0. Начиная с 38с С, проявляются аномалии: можно наблюдать частичное угнетение респирации, а кроме того максимумы, похожие не максимумы после прибавления субстрата. Зти максимумы обьясняют реактивной оксидацией в результате повышения температуры. Прибавление глюкозы к почве С еще ольше повышает зтот максимум. Вообще все аномалии у почвы С проявляются гораздо выразительнее.чем У компоста, который в течение созревания прошел стадией самосгревания.- Далее исследедовалась скорость респирации при переменах температуры во время опыта как в присутствии, так и в отсутсвии субстрата. На респирационной кривой можно после повышения ния температуры с 8 до 28о С наблюдать характерное переходное явление, которое в боих случаях, т. е. как для почры С, так и для компоста, отражается и на зндогенной респирации, и на респирационной кривй оксидации глюкозы (по отчислении зндогенной респирации).- В заключение высказыватмя нзгляд, что зто переходное явление предстанляет не аномалию, а общее явление, сопровождающее перемены температуры. Обсуждается его природа. лзучение влияния температуры на респирационные коивые, а в особенности изучение аномалтй и перходых явлений, может дать ценные ин?ормации об органическом вещестре почвы и о его минерализации.     

Effect of dicumarol on the growth of some soil microorganisms.

The effect of dicumarol on growth of selected soil bacteria: Azotobacter chroococcum, Arthrobacter globiformis, A. citreus and Bacillus megaterium was studied. The following minimum concentrations were inhibitory in vitro: Arthrobacter citreus--20 mug/ml., Bacillus megaterium--40 mug/ml., Azotobacter chroococcum--40 mug/ml. Arthrobacter globiformis--70 mug/ml. Cells of all microorganisms studied grown in the presence of dicumarol developed aberrant morphological forms.     

The effect of some herbicides on lactate dehydrogenase activity

The effect of herbicides N-(phosphonomethyl)glycine (glyphosate), 2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine (atrazine) and the respective commercial preparations “Round-up”, “Aminex”, and “Zeazin”, on the activity of lactate dehydrogenase isolated from germinating soybean seeds and beef heart were compared. The main aim of the work was to compare the effect of the herbicides on lactate dehydrogenase isolated from animal and plant material. Simultaneously the effect of herbicides and the respective commercial preparations was compared. Substantial differences resulting from the two comparisons indicate differences in the structure of active centres of lactate dehydrogenase isolated from animal and plant material, and also a considerable effect of additives and surfactants in commercial preparations.