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91.
Growth inhibition of plants suffering from Al toxicity is generally accompanied by impaired root development which can be quantitatively described by reduced specific root length (m g-1 dry root). In addition, the uptake of nutrients such as Mg and Ca is inhibited. Increased supply of either Mg or Ca can significantly diminish the negative effect of Al on root development and improve the Mg or Ca nutrition of the plants. The positive effect of Ca is well established but the effect of Mg has been observed in only a few plan species. Therefore, the effects of increasing Mg and Ca supply on Al toxicity in plants of seven monocots and eight dicots have been now examined in nutrient solution experiments. In general, Mg appears to be more effective than Ca in alleviating Al toxicity with the monocots, whereas the reverse is true for the dicots. Increased concentrations of Mg and Ca in solution seem to protect the plants against Al toxicity by improving the Mg or Ca nutrition and by alleviating the toxic effect of Al on root development. 相似文献
92.
Heavy metals in some Chinese herbal plants 总被引:1,自引:0,他引:1
The concentrations of nine heavy metals, cadmium, cobalt, copper, iron, manganese, nickel, lead, zinc and mercury in 42 Chinese
herbal medicinal plants were determined. Generally, all the samples studied had, relative to the other trace metals, higher
concentrations of iron, manganese, and zinc. The concentration range of the metals determined was comparable to that in many
of the East Asian vegetables and fruits. A few samples were found to contain relatively higher concentrations of the toxic
metals such as cadmium, lead, and mercury. This was probably caused by contamination during air-drying and preservation. 相似文献
93.
Xiaohong Zheng Tony D'Amore Inge Russell Graham G. Stewart 《Journal of industrial microbiology & biotechnology》1994,13(3):159-166
Summary Maltotriose transport was studied in two brewer's yeast strains, an ale strain 3001 and a lager strain 3021, using laboratory-synthesized14C-maltotriose. The maltotriose transport systems preferred a lower pH (pH 4.3) to a higher pH (pH 6.6). Two maltotriose transport affinity systems have been indentified. The high affinity system hasK
m values of 1.3 mM for strain 3021 and 1.4 mM for strain 3001. The low affinity competitively inhibited by maltose and glucose withK
i values of 58 mM and 177 mM. respectively, for strain 3021, and 55 mM and 147 mM, respectively, for strain 3001. Cells grown in maltotriose and maltose had higher maltotriose and maltose transport rates, and cells grown in glucose had lower maltortriose and maltose transport rates. Early-logarithmic phase cells transported glucose faster than either maltose or maltotriose. Cells harvested later in the growth phase had increased maltotriose and maltose transport activity. Neither strain exhibited significant differences with respect to maltose and maltotriose transport activity. 相似文献
94.
载脂蛋白多基因家族分子进化的研究 总被引:2,自引:2,他引:0
与脂质运输有关的载脂蛋白基因构成一个复杂的多基因家族。为探讨这种演化时间长的基因家族的进化规律,本文首先建立了一种在非均衡进化速率条件下计算系统发生树中任意分支长度的简易方法,并可在此基础上算出无根分支系统树中分歧年代的期望值。进一步对本文科10个种属共26种载脂蛋白的系统演作作了实际分析,结果提示:①ApoA-I'ApoA-IV,ApoE及ApoA-II的共同祖先可能在奥陶纪水生脊椎动物中就已存 相似文献
95.
T. R. Soderling S. E. Tan E. McGlade-McCulloh H. Yamamoto K. Fukunaga 《Developmental neurobiology》1994,25(3):304-311
One of the most active areas of neurobiology research concerns mechanisms involved in paradigms of synaptic plasticity. A popular model for cellular leaning and memory is long term potentiation (LTP) in hippocamus. LTP requires postsynaptic influx of Ca2+ which triggers multiple biochemical pathways resulting in pre- and postsynaptic mechanisms enhancing long term synaptic efficiency. This article focuses on an acute postsynaptic Mechanism that can enhance responsiveness of glutamate receptors. Evidence is presented that calcium/calmodulin/dependent protein kinase II, the major potsynaptic density protein at excitatory glutaminergic synapses, can phosphorylate glutamate receptors and enhance ion current flowing through them. 1994 John Wiley & Sons, Inc. 相似文献
96.
97.
研究了天然杀伤(NK)细胞对受致死剂量γ线照射的同系小鼠的造血调控作用。AMS/5小鼠经9Gyγ线全身照射后立即经尾静脉注射NK细胞(5×105),可明显提高受照小鼠30d活存率,照后8d小鼠骨髓中CFU-GM数量明显高于对照和脾细胞注射组,照射后30d,NK细胞注射组活存小鼠的骨髓有核细胞数和CFU-GM数已恢复到正常的76%─96%。病理组织学观察显示,输注NK细胞可使小鼠骨髓、脾脏的组织损伤程度减轻,造血功能增强,表现为造血灶数增多,造血细胞功能活跃,核分裂相增多,且涉及红系、粒系、巨核细胞系造血。NK细胞可能通过直接与造血干细胞相互作用或改善造血微环境等促进“内源性”造血功能,从而发挥对造血的正调控作用。提示NK细胞在小鼠造血功能的平衡维持中起重要作用。 相似文献
98.
对似近分析的一点改进及其拓广 总被引:2,自引:1,他引:1
本文给出了似近分析一个重要的改进,并将改进的似近分析推广为m维似近分析,同时给出了两个数学定理及其证明。根据多维似近系数的数学性质,提出了一种新的聚类方法,即逐步多维聚类法。实例分析证明,这种聚类法比二维系数聚类优越,聚类功能强,所获得的结果更为客观。 相似文献
99.
100.
本文对一类广义捕食系统生物种群生态常微模型建立几组无闭轨的充分条件,为开拓涉及该类模型制作参考类作全局制图定性的研究. 相似文献