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851.
Aluminum is a major constituent of most soils and limits crop productivity in many regions. Amelioration is of theoretical as well as practical interest because understanding amelioration may contribute to an understanding of the mechanisms of toxicity. In the experiments reported here 2-day-old wheat (Triticum aestivum L. cv Tyler) seedlings with 15-millimeter roots were transferred to solutions containing 0.4 millimolar CaCl2 at pH 4.3 variously supplemented with AlCl3 and additional amounts of a chloride salt. Root lengths, measured after 2 days in the test solutions, were a function of both Al activity and the cation activity of the added salt. Percent inhibition = 100 {Al3+}/({Al3+} + Km + α{C}β) where {Al3+} is the activity of Al3+ expressed in micromolar, {C} is the activity of the added cation expressed in millimolar, and Km (= 1.2 micromolar) is the {Al3+} required for 50% inhibition in the absence of added salt. For Ca2+, Mg2+, and Na+ the values of α were 2.4, 1.6, and 0.011, respectively, and the values for β were 1.5, 1.5, and 1.8, respectively. With regard to relative ameliorative effectiveness, Ca2+ > Mg2+ ≈ Sr2+ K+ ≈ Na+. Other cations were tested, but La3+, Sc3+, Li+, Rb+, and Cs+ were toxic at potentially ameliorative levels. The salt amelioration is not solely attributable to reductions in {Al3+} caused by increases in ionic strength. Competition between the cation and Al for external binding sites may account for most of the amelioration. 相似文献
852.
Glutamine Synthetase Isoenzymes in the Green Soil Alga Stichococcus bacillaris Naeg 总被引:4,自引:2,他引:2
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Two forms of glutamine synthetase (GS1 and GS2) have been separated from cells of Stichococcus bacillaris by fast protein liquid chromatography. The activities of the two isoenzymes were influenced by the composition of the media employed; thiol reagents were essential for stabilizing GS2 but they suppressed GS1 activity. The activity of each isoenzyme was, therefore, determined following separate purification procedures. Growth conditions influenced both isoenzymes; GS2 showed maximum activity under photoautotrophic conditions, whereas GS1 showed maximum activity under heterotrophic conditions. 相似文献
853.
The polychaete annelid Alvinella pompejana was discovered near the hydrothermal vents, recently explored in the Eastern Pacific Ocean. This worm is protected by a cuticle deeply transformed over certain areas of the body and some changes are due to the presence of a very special bacterial flora. The present work however deals mainly with the supercoiled collagen fibrils, which are well visualized in thin sections observed by transmission electron microscopy. This character strongly differentiates this species from other annelids and worms in general, the cuticle of which includes straight and apparently non-coiled collagen fibrils. This indicates that fibrils are extensible in Alvinella, possibly under physiological conditions, and that internal pressure and local volume variations are regulated according to principles which depart from what is recognized in other worms, where cuticular fibrils are considered as inextensible. Possible models of this cuticle are discussed and particularly aspects which show a relationship with certain liquid crystals. Very different factors may be involved in morphogenesis of such cuticles: microvilli distribution, self-assembly of collagen fibrils, mechanical constraints. An appendix recalls some classical data on worm cuticle geometry and presents an estimate of volume variations resulting from coiling of fibrils. 相似文献
854.
臭参中挥发性臭味的化学成分 总被引:3,自引:0,他引:3
臭参(Codonopsis sp.)俗称臭药、云南参、臭党参等,系桔梗科党参属云南特有植物种,种名待分类学家鉴定。其根具有特殊臭味,民间作为廉价滋补佳品,和肉、蛋一起煮食,具有补中益气,生津之功效。同属许多植物如党参(C.pilosula Nannf)、川党参(C.tangshan Oliv.)等的根,均为著名中药,但都没有臭参那种臭味。该植物的化学成分未见报道。为了解臭参植物的药用价值以及同党参、川党参等的相互关系,我们首先对臭参的挥发性臭味化学成分作了气相色谱-质谱法分析,现将结果简要报告如下。 相似文献
855.
856.
857.
丽江百合鳞茎细胞内贮藏物质的细胞形态学观察 总被引:4,自引:0,他引:4
丽江百合(Lilium lijiangenese L.J.Peng,sp nov.)引种栽培三年。鳞茎体积增大,中部鳞片细胞由平均12层增加到21层。细胞体积由平均86.5×79微米增加到97.5×89.7微米。细胞内含有两种贮藏颗粒,一种体积较大,椭圆形,另一种体积略小呈圆球形。较大者含有淀粉物质,较小者含有蛋白质、脂肪、多糖和少量核糖核酸。细胞内平均淀粉粒数由4.2个增加到8个,其体积由29.1×19.5微米增加到46.8×23.4微米。蛋白质颗粒数由平均12个增加到70个,体积稍有减小,由4.68—7.8微米减少到3.9—5.85微米。 相似文献
858.
用云南山楂(Crataegus scabrifolia(Franch.)Rehd.)成年树茎尖和实生芽两种不同发育阶段的材料为外殖体,诱导它们休眠芽萌动,丛生芽条并诱导芽条生根。实验结果如下:1.以成年态的云南山楂侧芽为外植体,培养在附加IAA 0.1—0.5mg/l+6-BA 1-2mg/l的MS培养基上可诱导芽的萌发;将芽继代培养在附加0.5—1mg/l 6-BA的SH或MS培养基上,40天后芽数增殖4—6倍;将芽条截下置于1/2MS培养基上,附加不同浓度的IAA或IBA,可得到50—80%的生根率。2.以实生芽为外殖体,在相同条件下,则20天后芽数增殖便可获4—6倍;98%以上生根。结果表明:云南山楂的幼年态要比成年态易脱分化和再分化。 相似文献
859.
香荚兰种子的无菌萌发试验 总被引:1,自引:0,他引:1
香荚兰(Vanilla planifolia)是兰科、香荚兰属植物,主产于湿热地区。香荚兰的果实是国际上重要的食用香料的原料。大约在1960年,我国引入香荚兰试栽。生产上,通常用扦插法繁殖;但如用种子繁殖,虽然结实较晚(约7至8年开始结实,较扦插苗晚4—5年),但结实期长,盛产期可维持约15年。而且,在杂交育种过程中,一定要用种子繁殖。 相似文献
860.
心不甘中甾体皂甙元的分离和结构鉴定(2) 总被引:2,自引:0,他引:2
自心不甘(Tupistra aurantiaca Wall et Backer)根的醋酸乙酯萃取物经硅胶柱层析分离除可得到1β、2β、3β、4β、5β、7α-hexahydroxyspirost-25(27)-en-6-one外,还得到7个游离的甾体皂甙元A—G,其中A及B分别为3-epiruscogenin及3-epi-neoruscogenin,F为△~(25(27))-pentrogenin(6)、C、D和E系新化合物,经IR、MS、~1H NMR及~(13)C NMR谱鉴定分别推定为ranmogenin A(3)、B(4)和C(5)(兰茂甙元甲、乙和丙)。 相似文献