Salinity and germination of annual Melilotus from the Guadalquivir delta (SW Spain)

The germination response to NaCl treatments has been studied in Melilotus seed populations collected from saline and non-saline soils in the Guadalquivir delta. The rank orders for salt tolerance and seed weight were the same in the threeMelilotus species living in this area:Melilotus messanensis>M. segetalis>M. indica. Within the species, differences in germination response to salinity were found inM. indica (6 populations) andM. segetalis (8 populations). The relationship between salt tolerance during germination and salinity of maternal habitat is discussed.     

Long-term responses of Melilotus segetalis to salinity. I. Growth and partitioning

Annual sweetclover plants [Melilotus segetalis (Brot) Ser.] were grown for a complete life cycle with and without saline (NaCl treatment of CE=15 dS m⁻¹). Growth and partitioning analyses were performed. Sequential harvests (every 15 d) during the life cycle, and separation of plant material into roots, stems, petioles, leaves and reproductive structures were carried out Salt treatment reduced growth during the early and middle stages of the life of the plant, but did not significantly affect RGR in the reproductive phase. The root–shoot allometric coefficient of salinized plants in the generative phase decreased more than in control plants. We suggest that salinity-induced growth reduction in M. segetalis was primarily a result of a lower unit leaf rate (ULR) despite an increased leaf area ratio (LAR). Earlier flowering, higher biomass allocation to shoot and greater reproductive investment, but similar relative growth rate (RGR), were some of the main characteristics of salt-stressed plants compared to controls during the reproductive phase, these apparently being associated with increased sink strength caused by developing flowers and fruits.     

Effects of clinorotation and microgravity on sweet clover columella cells treated with cytochalasin D

The cytoskeleton of columella cells is believed to be involved in maintaining the developmental polarity of cells observed as a reproducible positioning of cellular organelles. It is also implicated in the transduction of gravitropic signals. Roots of sweet clover ( Melilotus alba L.) seedlings were treated with a microfilament disrupter, cytochalasin D, on a slowly rotating horizontal clinostat (2 rpm). Electron micrographs of treated columella cells revealed several ultrastructural effects including repositioning of the nucleus and the amyloplasts and the formation of endoplasmic reticulum (ER) whorls. However, experiments performed during fast clinorotation (55 rpm) showed an accumulation (but no whorling) of a disorganized ER network at the proximal and distal pole and a random distribution of the amyloplasts. Therefore, formation of whorls depends upon the speed of clinorotation, and the overall impact of cytochalasin D suggests the necessity of microfilaments in organelle positioning. Interestingly, a similar drug treatment performed in microgravity aboard the US Space Shuttle Endeavour (STS-54, January 1993) caused a displacement of ER membranes and amyloplasts away from the distal plasma membrane. In the present study, we discuss the role of microfilaments in maintaining columella cell polarity and the utility of clinostats to simulate microgravity.     

Screening of the occurrence of copper amine oxidases in Fabaceae plants

Aim of this work was to find the best source for obtaining high amount of copper amine oxidase (EC 1.4.3.6) that can be further used for analytical or industrial applications. The study focused on plant enzymes, because they occur in much higher content in the starting material than the enzymes from other sources, have higher specific activity and are also more thermostable. Presence of the amine oxidase was tested in extracts from 4 to 7-d-old seedlings of thirty-four various Fabaceae plants. Amine oxidases from nine selected plants were purified by general method involving ammonium sulfate fractionation, controlled heat denaturation, and three chromatographic steps. Kinetic properties of the amine oxidases purified were tested with a wide range of substrates and inhibitors and were found to be very similar. Best purification yield, and total and specific activities were obtained for the enzyme from grass pea (Lathyrus sativus) throughout all purification steps. Hence, the grass pea extract was chosen as a suitable candidate for massive production of the amine oxidase. This revised version was published online in July 2006 with corrections to the Cover Date.     

Karyotype Analysis and Giemsa Banding of Melilotus suaveolens

The karyotype analysis and the Giemsa banding in Daghestan Sweetclover were carried out. The result shows that the chromosome number in each somatic cell is 2n=16. The formulas of karyotype and banding pattern are therfore 2n=16=12m+ 2sm+2sm(SAT) and 2n=16=8C+4CT⁺+2CT₊+2CTN, respectively.     

Does allelopathy involve in the association pattern of Trifolium resupinatum?

Indoor experiments demonstrated that allelopathic potential of rosette and flowering plants of qort is an important factor explaining the growth reduction of its associated species. Aqueous tissue extracts of flowering plants exhibited strong inhibitory effects on the germination percentage and radicle growth rate of the tested species as compared with those of vegetative plants. Under laboratory conditions, this inhibition was in agreement with toxicity assessments of soil samples collected from the rhizosphere of T. resupinatum L., where shoot and root dry mass of the tested species were significantly reduced. Detoxification of allelochemicals by presence of activated carbon can eliminate the inhibitory effects of the different extracts. This technique clarifies the occurrence of allelopathic interference by qort on seed germination and seedling growth, and hence suspects the allelopathic potential of qort in the growth reduction of associate species under field conditions along with competition. This revised version was published online in August 2006 with corrections to the Cover Date.     

Early trajectories of forest understory development on reclamation sites: influence of forest floor placement and a cover crop

We tested whether direct placement of forest floor material (FFM: litter, fibric, humus layers and surface mineral horizons) and sowing of a cover crop (Melilotus officinalis) could facilitate the establishment of native forest understory species at a reclaimed coal mine in Alberta, Canada. FFM was salvaged at two depths (15 and 40 cm) from a recently harvested native aspen forest and immediately placed at the same depths on the reclamation site. Total richness (approximately 61 species in 96 subplots) was similar in each of 3 years post‐placement; total richness for all 3 years combined was 87 including 34 typical boreal forest understory species plus 30 other natives. The deeper treatment reduced cover of all species, native and non‐native species in year 1. In year 3, the deeper treatment still had lower cover of non‐native species but had higher cover of forest understory species in years 2 and 3. The deeper treatment also resulted in lower species richness per plot, but only in year 1. In year 2 (when the biennial clover was at its tall stage), the cover crop treatment was associated with lower cover of non‐native species but did not affect the cover of native forest understory species. Direct placement of FFM can help facilitate establishment of a diverse native boreal forest understory in a reclaimed landscape. Although richness and cover may be initially higher with shallower salvage and placement, deeper salvage may ultimately be better for encouraging establishment of native forest understory species.     

草木犀石油醚提取物对小鼠巨噬细胞促炎介质的影响

目的研究草木犀石油醚提取物在体外的抗炎作用。方法采用小鼠巨噬细胞系RAW264．7建立炎症细胞模型,加入10μg/L的LPS培养液和不同浓度的草木犀石油醚提取物进行干预。ELISA法检测上清液中TNF-α,IL-1β,IL-6和NO的分泌量;实时荧光定量RT-PCR检测TNF-α,iNOS和COX-2的mRNA表达;Western印迹法检测COX-2蛋白的表达。结果草木犀提取物干预后细胞所分泌的炎性介质（TNF—α,IL-1β,IL-6和NO）与模型组相比均显著降低（P〈0．01）,并存在剂量依赖关系;RT-PCR结果显示干预后细胞TNF-α,iNOS和COX-2的mRNA表达水平显著降低（P〈0．01）,也存在剂量依赖关系;Western印迹结果显示草木犀石油醚提取物及地塞米松干预后COX-2蛋白水平明显降低（P〈0．01）。结论草木犀的石油醚提取物通过下调LPS诱导的巨噬细胞表达炎性介质而发挥其体外抗炎作用,且其下调作用呈剂量依赖性。     

黄花草木樨提取物抑菌活性初探

采用离体和活体试验方法分别测定了黄花草木樨不同溶剂提取物对12种植物病原真菌的抑菌活性.结果表明:各溶剂提取物对12种植物病原真菌均具有不同程度的抑菌活性,其中以乙酸乙酯提取物的抑菌活性最高,对油菜菌核病菌、玉米大斑病菌和白菜黑斑病菌抑制菌丝生长的EC50分别为0.62、0.83、0.64g/L,对稻瘟病菌和玉米大斑病菌抑制孢子萌发的EC50分别为0.67、0.97g/L.离体组织法测定表明其乙酸乙酯提取物对番茄灰霉病菌具有较高的保护和治疗作用,在浓度为5.0g/L时,防治效果分别为75.41%和59.18%(6d).活体试验表明乙酸乙酯提取物对小麦白粉病和小麦条锈病也有一定的保护作用,在浓度为10.0g/L时,防治效果分别为73.39%和63.27%.     

草木樨属根瘤菌的16S rDNA-RFLP分析

采用16S rDNA-RFLP分析方法对草木樨属根瘤菌进行了遗传多样性及系统分类研究。结果表明,3种限制性内切酶(HaeⅢ、HinfⅠ、MspⅠ)对所有供试菌株的酶切图谱类型组合只有2种。类型I的代表菌株CC-NWSX0003-1与豌豆根瘤菌(R.leguminosarum)的模式菌株USDA2370的序列相似性达到99.8%,在分类地位上属于根瘤菌属(Rhizobium)分支;类型Ⅱ的代表菌株CCNWGS0006与草木樨中华根瘤菌(Sinorhizobium meliloti)的16S rDNA相似性为100%,属于中华根瘤菌属(Sinorhizobium)分支。