Effect of salinity on growth and starvation-survival of a tropical Rhizobium strain

 The effect of salinity on growth, starvation-survival and recovery from salt stress of a Rhizobium sp. strain isolated from nodules of Acacia tortilis from a soil of Senegal was studied. Growth parameters of C-limited continuous cultures, grown in the presence and the absence of 342 mM NaCl, decreased in the saline medium and with increasing dilution rates. The survival capacity of starved cultures depended on the previous growth conditions: culturability of cells grown with salt was inversely related to growth rate, while culturability increased with increasing dilution rate for cultures grown without salt. Culturability of the cultures subjected to the double stress of starvation and salinity was reduced and a high percentage of cells entered the viable but nonculturable state. All the starved cultures were capable of regrowth when nutrients became available, thus showing that this strain can withstand long periods of nutrient deprivation in soil while maintaining the capacity for an active metabolism and a potential infectiousness toward an appropriate host. Received: 14 December 1998     

观赏植物试管苗玻璃化现象及防治研究进展

综述了离体培养中观察到有试管苗玻璃化现象的观赏植物种类,玻璃苗的形态解剖和生理生化特点,影响试管苗玻璃化的因素及克服试管苗玻璃化措施的研究进展。     

乳酸杆菌抑制致病菌及生物保鲜发酵剂特性评价

以15株乳酸杆菌为研究对象,动物双歧杆菌乳亚种BB-12作为对照,研究它们对肠道致病菌的抑菌特性.结果表明:9株菌对5株指示菌均有较好抑制作用,2株菌对金黄色葡萄球菌、肠炎沙门氏菌、大肠杆菌和蜡样芽孢杆菌均有抑制作用;以抑菌效果、凝乳状态、产酸性能为指标,筛选出4株菌,与嗜热链球菌ST-21组合制备生物保鲜发酵剂;通过...     

美味猕猴桃原生质体培养及植株再生技术研究

以美味猕猴桃雄株茎段愈伤组织为材料,分离原生质体,并培养在ＫＭ８Ｐ附加０．４５ｍｏｌ／Ｌ葡萄糖和０．０５ｍｏｌ／Ｌ蔗糖的培养基上,用低熔点琼脂糖包埋,６￣７ｄ发生第一次细胞分裂,培养２０ｄ的分裂率为１１．３％,在未添加新鲜培养液的情况下,原生质体再生的细胞可持续分裂至８０ｄ左右,并形成２￣３ｍｍ大小的愈伤组织,然后采用二步诱导分化法将原生质体来源的愈伤组织诱导分化出绿苗,再诱导生根,形成完整的小植     

浓缩嗜热链球菌的超微结构研究

为揭示超浓缩培养过程中茵体结构变化机制,采用微孔滤膜法对嗜热链球菌进行了超浓缩培养,研究了培养过程中pH值、茵数、LDH、LD含量和茵体超微结构的变化,结果表明茵体在超浓缩培养过程中存在着明显的形态变化,与茵体增殖和产酸规律密切相关。     

Isolation and biochemical diagnosis of cell lines of groundnut (Arachis hypogaea L) selected on glyphosate†

Three cell lines of groundnut (Arachis hypogaea L), an important oilseed legume, were selected on glyphosate using in-vitro culture techniques. The cell lines isolated through single as well as stepwise selection procedures showed c 20-fold increase in glyphosate tolerance as compared to the unselected control cell line. Studies on the biochemical mechanism of glyphosate tolerance in these cell lines showed a significant increase in the total extractable activity of the target enzyme, 5-enolpyruvyl shikimate-3-phosphate (EPSP) synthase (EC 2.5.1.19), which was further confirmed with immunological data. The over-expressed EPSP synthase activity was, however, subject to inhibition by glyphosate in vitro. Two other key regulated enzymes of the shikimic acid pathway, 3-deoxy-D -arabino heptulosonate 7-phosphate (DAHP) synthase (EC 4.1.2.15) and chorismate mutase (CM) (EC 5.4.99.5) did not show any change in specific activity in the selected cell lines. The enhanced activity of EPSP synthase in the tolerant cell lines was found to be stably inherited in the absence of selection pressure. © 1999 Society of Chemical Industry     

Glutathione transferases and herbicide detoxification in suspension-cultured cells of giant foxtail (Setaria faberi)

Glutathione transferases (GSTs) catalysing the conjugation of 1-chloro-2,4-dinitrobenzene, the chloro-s-triazine herbicide atrazine, the chloroacetanilide herbicides metolachlor and alachlor and the diphenyl ether herbicide fluorodifen have been identified in suspension-cultured cells derived from the grass weed giant foxtail (Setaria faberi Herrm.). In contrast to suspension-cultured cells of maize, where atrazine-conjugating GSTs are lost during de-differentiation, the GSTs active toward this herbicide in S. faberi plants were also expressed in cultures, suggesting that these isoenzymes are subject to different regulation in the crop and weed. As a result, glutathione conjugation was the major route of atrazine metabolism in S. faberi cultures. Activities of these GSTs were maximal three days after sub-culturing when the cells were dividing most actively, when they were determined to be in the order CDNB>alachlor>metolachlor= fluorodifen>atrazine. This indicated that GSTs which are enhanced during cell division can metabolise herbicides. On the basis of activity per mg protein, GST activities in the cultures were between 20 and 60-fold higher than those determined in the foliage of S. faberi seedlings. The GSTs with activity towards CDNB were resolved into three peaks following anion-exchange chromatography at pH 7·8 using Q-Sepharose. Peak 1 GSTs were not retained, while peak 2 and peak 3 were sequentially resolved with an increasing concentration of salt. Peak 1 GSTs showed activity toward metolachlor and atrazine but showed little activity toward fluorodifen. Peak 2 and peak 3 GSTs were active toward atrazine and metolachlor, with peak 3 being particularly associated with activity toward fluorodifen. The GSTs in these peaks were then further purified using S-hexyl-glutathione-agarose affinity chromatography. In each case, the affinity-bound fraction of the GSTs consisted of 28 kDa and 26 kDa polypeptides, suggesting that the GST isoenzymes in S. faberi cultures are composed of related subunits. Our results demonstrate that the GST isoenzymes involved in herbicide metabolism in suspension cultures of a grass weed show a similar level of complexity to that determined in maize cell cultures. © 1998 SCI     

Direct plant regeneration from mature leaf explants of pistachio, Pistacia vera L.

A protocol was developed for direct shoot and plantlet regeneration from in vitro regenerated leaf explants of male Pistacia vera L. cv. ‘Atl?’. Leaves excised from axenic shoot cultures of pistachio were used to induce organogenesis on a Murashige and Skoog (MS) medium with Gamborg vitamins supplemented with combinations of different concentrations of BAP and IAA. The highest adventitious shoot regeneration in 35% of the explants, with the number of shoots ranging from 2 to 3 per explant, occurred in the explants cultured during the establishment phase in the medium with 1 mg l⁻¹ IAA and 2 mg l⁻¹ BAP. For shoot multiplication, the highest number of new microshoot/explants (5.76) was obtained in a culture medium supplemented with 1 mg l⁻¹ BAP, but it was not significantly different from the number obtained at 2 mg l⁻¹ BAP. A high rooting frequency (84%) for microshoots was recorded on a medium supplemented with 2 mg l⁻¹ IBA. In vitro rooted plantlets were transferred to pots filled with a mixture of soil, sand and peat (1:1:1). They were weaned in a growth room and finally moved to a greenhouse. This protocol could be utilized for in vitro clonal propagation of this economically important plant.     

硼钙营养对柠檬幼苗光合生理及根系活力的影响

采用二因素五水平回归最优设计、砂培，两种ｐＨ环境（ｐＨ１５．６～５．８，ｐＨ２７．６～７．８），研究了Ｂ，Ｃａ不同浓度对柠檬幼苗生长、叶片叶绿素含量、光合强度及根系活力的影响，建立了相应的数学模型。结果表明，Ｂ，Ｃａ缺乏或过量降低叶绿素含量和光合强度。叶绿素含量最大时的叶Ｃａ／Ｂ分别为ｐＨ１下４９１，ｐＨ２下２９３；光合强度最大时的叶Ｃａ／Ｂ分别为ｐＨ１下５２５，ｐＨ２下２８５。Ｂ，Ｃａ浓度适量下降提高了根系活力，而Ｂ，Ｃａ浓度过量抑制了其活力，碱性环境的根系活力明显低于酸性环境。