1,721,479 research outputs found
Iron reduction and uptake by grapevine roots
No full textSome characteristics of Fe reduction and uptake by grapevine roots were studied by comparing them with K+ uptake and with ion uptake by oat roots. BPS inhibits Fe uptake by more than 90 percent both in grapevine and oat roots. However, the Fe reducing capacity of membrane vesicles “in vitro” is also inhibited by BPS. Compounds interfering with electron flows (DCMU, PMS, ferricyanide) also inhibit Fe uptake. Anaerobiosis increases the reducing activity of grapevine roots. Oligomycin inhibits Fe reduction in the presence of O2 and stimulates it under anaerobiosis. Rotenone inhibits Fe uptake both in aerobic and anaerobic conditions. Fe and K uptake rates by grapevine roots are not constant. A first phase at higher rate occurs within the first minutes, a second phase follows at a lower rate. With oat roots Fe behaves similarly, while K uptake occurs at a constant rate. Lowering the temperature from 30 to 0°C decreases the absorption of Fe and K by grapevine roots by about 50%. Fe uptake by oat roots decreases by 75 percent and K uptake by about 90 percent. Fe absorption by different grapevine species is characterized by wide differences in the kinetic constants (Vmax and Km) and in the response to changes of pH. The biochemical basis of Fe reduction and the distinctive features of Fe uptake by grapevine roots are discussed
Scienze sociali e diritto. Terni, tendenze e connessioni, Guido Maggioni (a cura di), 1995 ; I diritti nascosli. Aproccio antropologico e prospettiva sociologica, Alberto Giasanti et Guido Maggioni (a cura di), 1995
No full textScienze sociali e diritto. Terni, tendenze e connessioni, Guido Maggioni (a cura di), 1995 ; I diritti nascosli. Aproccio antropologico e prospettiva sociologica, Alberto Giasanti et Guido Maggioni (a cura di), 1995. In: Droit et société, n°32, 1996. Norme, règle, habitus et droit chez Bourdieu. p. 236
Scienze sociali e diritto. Terni, tendenze e connessioni, Guido Maggioni (a cura di), 1995 ; I diritti nascosli. Aproccio antropologico e prospettiva sociologica, Alberto Giasanti et Guido Maggioni (a cura di), 1995
No full textScienze sociali e diritto. Terni, tendenze e connessioni, Guido Maggioni (a cura di), 1995 ; I diritti nascosli. Aproccio antropologico e prospettiva sociologica, Alberto Giasanti et Guido Maggioni (a cura di), 1995. In: Droit et société, n°32, 1996. Norme, règle, habitus et droit chez Bourdieu. p. 236
Extraction and preliminary characterization of microsomal (Mg2++K+)-ATPase activity of grapevine roots
No full textThe microsomal fraction extracted from grapevine roots obtained from woody cuttings possesses Mg2+-dependent, monovalent cation-stimulated ATPase activity. Addition of BSA, PVPP, choline-Cl, ethanolamine, glycerol-1-P besides EDTA and DTT to the homogenizing medium as preservative compounds was required in order to achieve a successful isolation. When microsomes were extracted according to Hodges and Leonard (1974) by homogenizing root tissue in the presence of EDTA and DTT, the enzyme activity exhibited inhibition by Mg2+ only partially relieved by K+, and properties of acid phosphatase rather than ATPase. Cation-stimulated ATPase of microsomes protected during homogenization was further characterized and it showed optimum activity at pH 7.0 in the presence of Mg2+ plus K+. It was specific as a triphosphatase and Mg2+, rather than other divalent cations, was preferred as a cofactor. As monovalent stimulating cation, only NH4+ could substitute for K+ with equivalent efficiency. The kinetics of K+ stimulation showed a biphasic pattern. Biochemical bases of ion uptake by grapevine seem to be similar to those clarified for annual plant
PROBLEMS OF PLANT NUTRITION LINKED TO SOIL-ROOT INTERACTION
No full textMechanisms characterizing the relationships between root and soil with effects on the mineral nutrition of plants are analyzed. Root activities (acidification, reduction, chelation and exudate release) able to modify the rhizosphere are described. The modulatory actions exerted by soil components (water, oxygen and humic substances) on the biochemical mechanisms located at the cell membranes and involved in plant nutrition are also considered
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
POTASSIUM FLUX IN CORN ROOTS DURING AUGMENTATION OF ION UPTAKE
No full textAeration of submersed corn roots doubles the subsequent uptake rate of ions. Potassium uptake (86Rb) by excised and intact roots before and after augmentation was measured, and potassium losses by roots at different temperatures or in the presence of dinitrophenol was followed. Relevant effluxes of potassium follow excision and/or submersion of roots, and a metabolism-dependent process must be carried out by roots in order to recover the control of membrane permeability. Moreover, we show that corn hybrids of different maturity classes differ not only for initial uptake rate but also for the ability to recover control of membrane permeability
Free space binding and uptake of ions by excised roots of grapevines
No full textThe uptake of of potassium and sulphate ions by excised roots of two species of Vitis (V. vinifera cv Verduzzo trevigiano and the hybrid rootstock V. berlandieri x V. rupestris 1003 P) was studied and compared. It si shown that important differences between genotypes can occur in the binding of ions in the free space
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