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Possibile ruolo di una ATPasi K+ sensibile nei processi di germinazione in semi di rapanello
No full textEffetto in vitro di lipidi polari sulla attività ATPasica Mg2+, K+ dipendente presente in preparazioni di membrana di semi di ravanello
No full textEffects of ABA, GA3 and FC on the developement of potassium uptake In germinating radish seeds
No full textGermination of Rhaphanus sativus seeds is accompanied in its early phase by a consistent loss to the medium of the main cations. During the first ten hours there is a general efflux of K+, Na+, Mg2+ and Ca2+, while in the following period K+ is actively taken up so that after eighteen hours almost no K+ is detected in the external medium. When seed germination is stimulated by fusicoccin (FC) the development of uptake capacity is markedly anticipated. Moreover, inhibition of seed germination by abscisic acid (ABA) inhibits the development of K+ uptake. The ABA-induced inhibition is reversed by FC and also, even if to a lesser extent, by gibberellic acid (GA3). Preliminary data suggest that a K+ activated ATPase present in membrane preparation is involved in the mechanism of active K+ uptake in the seeds
Effects of FC, GA and ABA on the developement of K uptake in germinating radish seeds
No full textEffects of FC, GA3 and ABA on the development of K uptake in germinating radish seeds
Germination of Rhaphanus sativus seeds is accompanied in its early phase by a consistent
loss to the medium af the main cations. During the first ten hours there is a general efflux .
of K+, Na+, Mg2+, C2+ while inn the following period K+ is actively assumed so that at
eighteenth hour almost no K+ is detected in the external medium.
When seed germination is stimulated by fusicoccin (FC) the development of the capacity of
uptake is markedly anticipated .Moreover inhibition of seed germination by abscisic acid
(ABA) inhibits the development of K+ uptake. The ABA-induced inhibition is reversed by FC and
also, even it to a lower extent, by gibberellic acid GA3.
K+ uptake in germinating radish seed depends on energetic metabolism and on protein synthesis
Respiratory inhibitors such N, N'-dicydohexylcarbodiimide(DCCD) and salicylhydroxamic acid
induced a continuous loss of K from the seed. The presence in the germination medium
of inhibitor of RNA and of protein synthesis such as 3'd-adenosine{cordycepin) and
ciclohexymide (CHI) inhibits the development of K+ uptake .These data suggest that a FC-sen-
sitive, metabolism dependent mechanism of K+ uptake is strictly correlated to the development
of the early phase of germination.
Preliminary data suggest that a K+ activated ATPase present in plasmalemma preparations is
involved in the mechanism of active K+ uptake in the seeds. Lado et al. (Physiol Plantarum
34 ,359 , 1975) showed that FC-induced promotion of germination of dormant seeds is accompanied
by marked drop of the pH in the incubation medium, thus 'suggesting that
the regulation of a H+/K+ exchange mechanism plays an important role in the process of
seed germination
Fe uptake mechanism in Fe-efficient cucumber roots
No full textFe-efficient plants respond to iron stress both by morphological and physiological modifications. In roots of a Fe-efficient plant (Cucumis sativus L.) grown in the presence or in the absence of iron, the capacity to acidify the external medium, change in the transmembrane electrical potential, and the ATPase activity have been determined. Roots from plants grown in the absence of iron showed a great capacity to acidify the external medium, a higher transmembrane electrical potential difference (−145 millivolts, versus −105 millivolts), and a higher ATPase activity (+30%). The administration of Fe2+, but not Fe3+, caused a block of the acidification capacity, a great decrease in the transmembrane electrical potential difference in root cells, and a large inhibition of the ATPase activity of isolated microsomal membrane vesicles
Changes of NAD and NADP dependent Glutamate dehydrogenase activity after ammonia addition to Rhodotorula gracilis cells growing in presence of nitrate
No full textEffects of Cr on proton extrusion,potassium uptake and transmembrane electric potential in maize root segments
No full textAbstract Proton extrusion of maize root Zea mays segments, was inhibited by the presence of Cr (o.n. + 6; present in solution as CrO42‐, Cr2O72‐) in the incubation medium: the minimum inhibiting concentration was 2 × 10−3 mol m−3 and the inhibition progressively increased with Cr concentration. Cr inhibited proton extrusion. Also, when this activity was stimulated by the presence of K+ or fusicoccin (FC) in the incubation medium, the K+ and FC stimulating effect was still present when proton extrusion was inhibited by Cr. In addition, Cr inhibited K+ uptake. This inhibition was higher (50%) at K+ concentrations up to 1 mol m−3 lower (15%) at higher K+ concentrations. This result indicates that the system responsible for K+ uptake operating at low K+ concentrations is more sensitive to Cr inhibition. Cr had no effect on transmembrane electric potential (PD). The depolarizing and hyper‐polarizing effect of K+ and FC, respectively, were not affected by Cr; but Cr enhances the depolarizing effect of the uncoupler carbonylcyanide m‐chlorophenylhydrazone (CCP). These results indicate that Cr inhibited the proton translocating mechanism coupled with K+ uptake, but did not change the net transport of charges through the plasmalemma. The Cr effect is discussed, taking into account the possibility of a direct effect of Cr at the membrane level or, alternatively, of an effect on some metabolic processes controlling membrane function
Changes in form of elongation factor 1 during germination of wheat seeds
No full textTwo forms of EF-1 are present in the high-speed supernatant fraction from wheat embryo homogenate. In embryos from dry seeds EF-1H is 55% of the total amount of EF-1, while after 40 h of germination this form completely disappears. When germination and protein synthesis are accelerated by means of 6-benzyladenine, the rate of conversion of EF-1H is increased. On the other hand, the block of germination and of the evolution of protein synthesis by abscisic acid, block this conversion; the block of water uptake, that stops germination and causes a decrease in protein synthesis, reverses the conversion of EF-1H to EF-1L, increasing EF-1H from 15% to 40% of the total
Potassium-dependent increase in RNA and protein synthesis in the early phase of incubation of the thermodormant Phacelia tanacetifolia seeds
No full textThe seeds of Phacelia tanacetifolia Benth. cv Bleu Clair incubated at 30°C in the dark did not germinate and did not activate K+ uptake capacity. The administration of 1 millimolar K+ in the early phase of incubation stimulated RNA and protein synthesis. The possible role of K+ in promoting the marcromolecular syntheses during the early phase of germination is discussed
A poly(U)-binding factor stimulating EF-1 activity in the wheat germ soluble fraction
No full textA poly(U)-binding activity is present in the high-speed supernatant fraction of embryo homogenates from wheat seeds. The factor responsible for such activity was found to have a stimulatory effect on the elongation factor 1 (EF-1). It copurifies with EF-1L, the lighter form of EF-1, through Sephadex G-200, DEAE-cellulose, hydroxyapatite and poly(U)-Sepharose 4B column chromatography. The two factors could be separated only through a heating step which destroyed EF-1 activity whilst leaving most of the poly(U)-binding activity unaltered
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