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111.
Calcium ions serve as a second messenger in signal transduction and metabolic regulation. Effects of Al on calcium homeostasis remain to be elucidated. Short-term net 45Ca2+ uptake by Amaranthus tricolor protoplasts was monitored from uptake media prepared to test the influence of pH, Al, and various inhibitors. Accumulation of 45Ca2+ increased during the first 3 to 6 minutes and then leveled off or declined. Al and Ca2+ channel blockers (verapamil and bepridil) decreased net 45Ca2+ uptake. This decrease was more pronounced when Al and bepridil were both present in uptake media, but Al did not aggravate verapamil-induced reduction of net 45Ca2+ uptake. Erythrosin B and calmidazolium each increased net 45Ca2+ uptake, probably by interfering with Ca2+ efflux. This effect was undetectable in the presence of Al. Mycophenolic acid decreased net 45Ca2+ uptake; guanosine alleviated this effect. Al-induced reduction of net 45Ca2+ uptake was not aggravated by mycophenolic acid. Net 45Ca2+ uptake was generally less at pH 4.5 than at 5.5 for all treatments. It is concluded that Al ions affect net 45Ca2+ uptake by binding to the verapamil-specific channel site that is different from the bepridil-specific one, as well as by interfering with the action of guanosine 5′-triphosphate-binding proteins. 相似文献
112.
Arsenic uptake, translocation and speciation in pho1 and pho2 mutants of Arabidopsis thaliana 总被引:2,自引:0,他引:2
Arsenate [As (V)] is taken up by phosphate [P (V)] transporters in the plasma membrane of roots cells, but the translocation of As from roots to shoots is not well understood. Two mutants of Arabidopsis thaliana (L.) [( pho1 , P deficient) and ( pho2 , P accumulator)], with defects in the regulation and translocation of P (V) from roots to shoots, were therefore used in this study to investigate uptake, translocation and speciation of As in roots and shoots of plants grown in soil or nutrient solution. The shoots of the pho2 mutant contained higher P concentrations, but similar or slightly higher As concentrations, in comparison with the wild type. In the pho1 mutant, the P concentration in the shoots was lower, and the As concentration was higher, in comparison with the wild type. Both pho2 and the wild type contained mainly As (III) in roots and shoot (67–90% of total As). Arsenic was likely to be translocated by a different pathway to P (V) in the pho2 and pho1 mutants . Therefore, it is suggested that As (III) is the main As species translocated from roots to shoots in Arabidopsis thaliana. 相似文献
113.
114.
The changes in nutrient content of grain tissues and seedling parts of two wheat genotypes (Triticum aestivum L., Excalibur and Janz) with low or high seed Zn content were followed from imbibition to early seedling development (12 days). The grains were separated into seed coat, endosperm and embryo, while the seedlings were separated into roots and shoots. The dry weight of the seed coat did not change throughout the experimental period, whereas the endosperm weight declined rapidly from day 4 onward. The weight of embryo did not show any difference between and within cultivars. About a half of seed Zn was remobilised into shoot and roots during 12 days of growth, regardless of the initial seed Zn content in both genotypes. The seed coat contained 55–77% of the total seed nutrients in the two wheat genotypes, except in the case of S (around 40%). Manganese, Fe, Ca, K, and P were remobilised effectively from the seed coat as well as from the endosperm, while remobilisation of Zn and Cu was relatively less from the seed coat than from the endosperm. After 10 days of growth, all nutrients monitored were completely remobilised from the endosperm. Remobilised K was directed primarily into shoots; an increase in K content in shoots was relatively higher than the accumulation of dry matter, with a consequent increase in K concentration in shoot tissue. The remobilisation of some nutrients (eg. Fe, Ca and Zn) from various grain tissues during inbibition, germination and early growth is different from the remobilisation in more mature plants. 相似文献
115.
Kinetic parameters of Zn uptake were determined for wheat plants(Triticum aestivum cvs Excalibur and Gatcher, and Triticum turgidumconv. durum cv. Durati) pre-grown at deficient or sufficientZn supply and with 0 or 4 mg m-3 sulphonylurea herbicide chlorsulfuron(2-chloro-N-(((4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino)carbonyl)-benzenesulphonamide].Net Zn uptake generally showed a saturable response to increasingsolution Zn concentrations; this response fitted a modifiedMichaelis-Menten equation incorporating the Cmin term (solutionconcentration when net uptake is 相似文献
116.
The uptake and distribution of 65Zn and 54Mn by wheat (Triticumaestivum cv. Aroona) was investigated. Plantswere grown in achelate-buffered nutrient solution with either sufficient Znand Mn, low Zn or low Mn. A single representative seminal rootfrom 14-d-old and 42-d-old plants was dual-labelled with 65Znand 54Mn. The 14-d-old plants were harvested every 10 min from10140 min of labelling, whilst the 42-d-old plants wereharvested after 2 h of labelling. At harvest, each plant wasseparated into leaves, main stem, unexposedroots, and tillers.In addition, the crown was separatedfrom the stem in the 14-d-oldplants In the control plants labelled at 14 d, 65Zn was firstdetectedand accumulated in the crown of the roots after 4060min. Labelled Zn was then detected in the stem, followed bythe leaves. The oldest and youngest leaves received less 65Znthan the second and third oldest leaves. The plants grown underlow Zn conditions accumulated more 65Zn in their older leavesand transferred 63Zn to the unexposed roots. Distribution of54Mn was similar in the controls to that of 65Zn, except theolder leaves received no HMn, At the second harvest, a similardistribution pattern of 65Zn and 54Mn was observed with regardto leaf age. Large amounts of 65Zn and 54Mn were detected withinthe unexposed roots of all treatments. It is suggested thatthe distribution of root-supplied Zn and Mn may be determinedby micronutrient status and its relationship with leaf transpirationrates. Key words: Distribution, manganese, vegetative growth, wheat, zinc 相似文献
117.
Maja Majerić Amir Avdagić Zdenko Hameršak Vitomir Šunjić 《Biotechnology letters》1995,17(11):1189-1194
Summary 2-Methyl-(4-tert-butyl)cinnamaldehyde (1) was reduced by Saccharomyces cerevisiae (baker's yeast) to S-3-(4-tert-butyl)-phenyl-2-propanol (4) in high chemical and very high optical yield (e.e. 99%). Chlorination of 4 to 5, and alkylation of the corresponding cyclic amines complete this short enantioselective synthesis of S-1-(l'-pyperidino)-2-methyl-3-(4tert-butyl)-phenyl-propane (6) and S-1-(1'-(3,5-cisdimethyl)morpholino)-2-methyl-3-(4-tert-butyl)-phenyl-propane (7), the S-enantiomers of fenpropidine and fenpropimorph, commercialy important systemic fungicides. 相似文献
118.
Assessment of the Zn status of chickpea by plant analysis 总被引:1,自引:0,他引:1
Chickpea (Cicer arietinum L.) is extensively grown in areas where soils are deficient in zinc (Zn). To determine the response of chickpea to Zn nutrition and to diagnose Zn status in plant tissue, two glasshouse experiments were conducted using Zn-deficient siliceous sandy soil. In Experiment 1, two genotypes of desi chickpea (Dooen and Tyson) were grown at five Zn levels (0, 0.04, 0.2, 1.0 and 5.0 mg kg-1 of soil). After 4 weeks, no difference in growth and no visible symptoms of Zn deficiency were detected. After 6–8 weeks of growth, chlorosis of younger leaves and stipules occured in the Zn0 treatment, with shoot dry weight being only 24% of that recorded at the highest Zn level. Root growth increased from 0.52 g/plant when no Zn was applied to 1.04 g/plant in the treatment with 0.2 mg Zn kg-1 of soil; no response to further increase of Zn fertilization occurred. Zinc concentration in the whole shoot increased significantly with increased in Zn application. The critical Zn concentration in the shoot tissue, associated with 90% of maximum growth, was 20 mg kg-1 for both genotypes at flowering stage.In the second experiment, two genotypes of desi chickpea (Tyson and T-1587) were grown at three Zn levels (0, 0.5 and 2.5 mg kg-1 of soil) under two moisture regimes (field capacity 12% w/w, and water stress 4% w/w). Shoot growth was influenced by both Zn supply and water stress. The effect of water stress was severe in the 0.5 and 2.5 mg Zn treatments where shoot dry matter was reduced 52 and 46%, respectively. T-1587 was less sensitive to Zn deficiency and produced higher shoot dry weight than Tyson in the Zn0 treatment. Zinc concentration in shoots increased from 5 mg kg-1 when no Zn was applied to 40 mg kg-1 at the highest Zn level. The critical Zn concentration in shoots was 21 mg kg-1.The results of the two experiments showed that the critical concentration for Zn did not differ amongst the three cultivars used and was not affected by soil moisture. Similar studies should be undertaken with a wider number of genotypes to discover if a critical concentration of 20–21 mg kg-1 in the shoot can be used to diagose the Zn status of chickpea genotypes. 相似文献
119.
120.
Procházka Zdenko Žertová Miroslava Slaninová Jiřina 《International journal of peptide research and therapeutics》2000,7(3):179-185
Summary Solid phase technique on p-methylbenzhydrylamine resin was used for the synthesis of eight analogs of oxytocin and 8-D-homoarginine
vasopressin with the non-coded amino acids L- or D-2,3,4,5,6-pentamethylphenylalanine and L- or D-4-phenylphenylalanine in
position 2. The preparation of the above mentioned non-coded amino acids is described as well. All eight analogs were found
to be potent inhibitors of oxytocin activity in the uterotonicin vitro test in the absence of Mg2+ ions. In the uterotonic testin vitro in the presence of Mg2+ and in the testin vivo, their potency is strongly decreased or completely abolished. The substances are also weak pressor inhibitors. The L or D
configuration does not seem to influence the activity significantly.
Abbreviations: All the chiral amino acids unless otherwise stated are of the L-series. Phe(4-Ph) denotes the 4-phenylphenylalanine, Phe(pentaMe)
the 2,3,4,5,6-pentamethylphenylalanine, Har the homoarginine, DMF dimethylformamide, OHBT 1-hydroxybenzotriazole and DCC dicylohexyl-carbodiimitz.
The Nomenclature and symbols of the amino acids and peptides obey the published recommendations: IUPAC-IUB Joint Commission
on Biochemical Nomenclature: Eur. J. Biochem., 138 (1984) 9. 相似文献