274 research outputs found
The rhizosphere as a site of biochemical interactions among soil components, plants and microorganisms
No full text
Action of soil humic matter on plant roots: Stimulation of ion uptake and effects on(Mg2++K+) ATPase activity
No full textThe effects of soil humic matter on the uptake of ions by oat roots and on the (Mg2++K+) ATPase activity, responsible for energy transduction for ion transport at cell membrane, were studied. Four-day-old roots treated for 8 h with unfractionated humic solution (50 μg org C × ml-1) took up K+ and SO4staggered-2 ions at rates, respectively, 33% and 106% higher than the controls. Similar effects were caused by humic and fulvic acids, and by the hot-acid soluble and hot-acid insoluble fractions prepared from humic acids. At org C concentration higher than 1 μg ml-1, the humic extract inhibited both Mg2+ dependent and K+-stimulated ATPase activities of microsomes isolated from roots. At 0.33-1 μg org C ml-1, the Mg2+-dependent activity was inhibited, whereas the activity stimulated by K+ increased. Humic acids and the acid-insoluble fraction inhibited the ATPase activity more than fulvic acids and the acid-soluble fraction. Preliminary results of SDS - PAG electrophoresis of membrane proteins showed two polypeptides associated with membrane of humus treated roots, which where absent in the control. Differences between the two phenomena and structure-activity relationships will be discussed. © 1987
Effect of NO3- Cl- and DIDS on H+-ATPase of plasmamembrane vesicles isolated from corn root
No full textAnion effect on ATP-dependent proton transport in plasma membrane vesicles isolated from corn roots
No full textProton-translocating ATPase activity in plasma membrane vesicles from roots of grapevine seedlings
No full textMicrosomal vesicles isolated from grape (Vitis vinifera, cv. Verduzzo) roots were shown to possess ATP-dependent and vanadate-inhibited proton-translocating activity which was inhibited 30% by oligomycin and was insensitive to nitrate. Contamination by mitochondrial H+-ATPase activity was strongly reduced by modifying the extraction procedure and by collecting vesicles with density lower than 1.18 g × cc-1 after centrifugation of microsomes for 2 h at 95 000 × g on a 40% sucrose cushion. Proton transport was inhibited 65% by 200 μM vanadate. The half-maximal inhibition occured at 100 μM. Optimum of the proton transport activity pH was 6.5 and the Mg:ATP complex was strongly preferred substrate. Intravesicular acidification was dependent on the anion accompanying K+ ions (Br- > Cl- > NO3 - ≫ SO4 2- > IDA-) and it was stimulated by K+ ions, as shown by addition of K-IDA after incubation of vesicles with BTP-Cl or BTP-NO3. Enzymatic hydrolysis of Mg:ATP was stimulated 42% by K-IDA and inhibited 76% by vanadate. Oligomycin and nitrate showed almost no effect (16 and 5% inhibition, respectively). Results indicate that membrane vesicles isolated by this procedure from grape roots mainly derive from the plasma membrane representing the necessary material to study basal phenomena of mineral nutrition of grape plants. Agronomic and ecological adaptability and genetic variability make grape cultivars a good plant material to study factors controlling nutrition efficiency and regulation. © 1990
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