Real-time PCR detection of Holophagae (Acidobacteria) and Verrucomicrobia subdivision 1 groups in bulk and leek (Allium porrum) rhizosphere soils

In the light of the poor culturability of Acidobacteria and Verrucomicrobia species, group-specific real-time (qPCR) systems were developed based on the 16S rRNA gene sequences from culturable representatives of both groups. The number of DNA targets from three different groups, i.e. Holophagae (Acidobacteria group 8) and Luteolibacter/Prosthecobacter and unclassified Verrucomicrobiaceae subdivision 1, was determined in DNA extracts from different leek (Allium porrum) rhizosphere soil compartments and from bulk soil with the aim to determine the distribution of the three bacterial groups in the plant-soil ecosystem. The specificity of the designed primers was evaluated in three steps. First, in silico tests were performed which demonstrated that all designed primers 100% matched with database sequences of their respective groups, whereas lower matches with other non-target bacterial groups were found. Second, PCR amplification with the different primer sets was performed on genomic DNA extracts from target and from non-target bacteria. This test demonstrated specificity of the designed primers for the target groups, as single amplicons of expected sizes were found only for the target bacteria. Third, the qPCR systems were tested for specific amplifications from soil DNA extracts and 48 amplicons from each primer system were sequenced. All sequences were > 97% similar to database sequences of the respective target groups. Estimated cell numbers based on Holophagae-, Luteolibacter/Prosthecobacter- and unclassified Verrucomicrobiaceae subdivision 1-specific qPCRs from leek rhizosphere compartments and bulk soils demonstrated higher preference for one or both rhizosphere compartments above bulk soil for all three bacterial groups.     

Genotypic variation in sulphur assimilation and metabolism of onion (Allium cepa L.). II: Characterisation of ATP sulphurylase activity

To investigate the regulation of sulphur (S)-assimilation in onion further at the biochemical level, the pungent cultivar W202A and the milder cultivar Texas Grano 438 PVP (TG) have been grown in S-sufficient (S⁺; 4 meq S⁻¹) or S-deficient (S⁻; 0.1 meq S⁻¹) growth conditions, and tissues excised at the seedling stage (pre-bulbing; ca. 10-weeks-old) and at the mature stage (bulbing; ca. 16-weeks-old). S-supply negatively influenced adenosine-5′-phosphosulphate (APS) reductase (APR) enzyme activity in both cultivars at bulbing only, and a higher abundance of APR was observed in both cultivars at bulbing in response to low S-supply. In contrast, S-supply significantly influenced ATP sulphurylase (ATPS) activity in leaf tissues of W202A only, and only at bulbing, while an increase in abundance in response to high S-supply was observed for both cultivars at bulbing. To investigate the regulation of the ATPS enzyme activity and accumulation further, activity was shown to decrease significantly in roots at bulbing in the S-deficient treatment in both cultivars, a difference that was only supported by western analyses in W202A. Phylogenetic analysis revealed that AcATPS1 groups in a broad monocot clade with the closest sequences identified in Sorghum bicolour, Zea mays and Oryza sativa, but with some support for a divergence of AcATPS1. Detection of ATPS in leaf extracts after two dimensional gel electrophoresis (2-DE) revealed that the protein may undergo post-translational modification with a differential pattern of ATPS accumulation detected in both cultivars over the developmental progression from the seedling to the bulbing stage. Treatment of leaf extracts of W202A to dephosphorylate proteins resulted in the loss of immuno-recognised ATPS spots after 2-DE separation, although enzyme activity was not influenced. These results are discussed in terms of the tiers of control that operate at the biochemical level in the reductive S-assimilation pathway in a S-accumulating species particularly during the high-S-demanding bulbing stage.     

Priming responses of leek (Allium porrum L.) seeds to different dissolved oxygen levels in the osmoticum

Leek seeds (Allium porrum L.) cv. Winterreuzen were treated for 5 days in stirred bioreactors containing a -1.0 MPa polyethylene glycol (PEG 6000) solution. The level of dissolved oxygen was controlled from zero to approximately two and a half times that of saturation with respect to atmospheric air by bubbling through 0₂/N₂ gas blends from 0% O₂ to 50% O₂. The treatment with 0% O₂ (i.e. bubbling with N₂) gave no reduction in germination time compared to untreated seeds after allowing for the time for water imbibition. As the proportion of oxygen was increased, a rapid reduction was observed until a concentration equivalent to air was used. Further increases to the maximum, produced only a marginal further improvement. The reduction in germination times for seeds that had been cabinet dried was longer for all treatments due to the time required for re-imbibition of water but the general response to priming was the same as with undried seeds. Only dried seeds treated with air or higher oxygen concentrations showed enhanced synchronicity of germination times. The percentage germination of seeds from all treatments was the same, including the treatment with nitrogen gas. These tests help to explain the recently reported advantages of using enriched air for seed priming and are one of the necessary protocols for ensuring satisfactory bulk priming.     

沙枣和柠条种子萌发期耐盐性研究

采用室内控制实验的方法,系统研究了沙枣和柠条种子萌发、生长、活力以及生理过程;对萌发、生长及活力指标与盐胁迫进行相关与回归分析,发现了实验室条件下沙枣和柠条种子萌发期的耐盐临界值;对生理指标与盐胁迫,生理指标与相应的萌发及生长指标进行相关性分析,在生理水平对沙枣和柠条种子萌发期对盐胁迫的响应进行了解释。主要结果包括：(1)胚根相对干重含水量与盐胁迫无相关性,初始萌发时间、休眠率以及死亡率与盐胁迫呈显著正相关,其它指标均与盐胁迫呈显著负相关;(2)胚根相对干重含水量与萌发种子初期生长无相关性,休眠率、死亡率与萌发率呈显著负相关,其它指标均与初期生长呈显著正相关;(3)受盐胁迫的抑制程度：萌发速度>萌发启动>萌发率;胚根生长>胚轴生长>萌发率;(4)种子萌发期,沙枣耐盐性强于柠条,两者耐盐临界值均高于0.1 mol·L^-1。     

盐胁迫对蓝蓟种子萌发及早期幼苗的影响

研究了不同浓度盐(NaCl)处理对蓝蓟种子发芽势、发芽率及幼苗生长的影响。结果表明:(1)不同盐胁迫处理对蓝蓟种子的萌发具有显著影响。随着盐处理浓度的增加,发芽率呈下降趋势,蓝蓟在无盐环境(蒸馏水)和低盐环境中(0.05 mol/L)长势最好、发芽率最高、发芽速度最快。(2)将不同盐溶液处理5 d的未萌发种子转移到蒸馏水后,蓝蓟种子的萌发能力均可恢复,原来较高盐浓度(0.3 mol/L～0.5 mol/L)下的种子在恢复后,其萌发恢复率均在75%以上,发芽率基本上随着原浓度的升高呈上升的趋势。研究表明,NaCl处理对蓟种子没有造成伤害,其抑制萌发是通过渗透效应而不是离子毒害。     

黄瓜种子萌发过程中Ca~(2 )分布的变化

采用细胞化学方法 ,研究了黄瓜种子中贮藏Ca2 的分布特点及其在萌发过程中的变化动态。干种子的子叶细胞中贮藏有大量的蛋白体、油脂体 ,Ca2 沉淀颗粒大量分布于胞质、胞间隙以及细胞质膜上。大多数蛋白体中有 1至数个圆球形或椭圆体形含Ca2 的球状晶体。相比之下 ,胚芽和胚根细胞中Ca2 较少。种子萌发早期 ,子叶中的贮藏钙及晶体溶解释放出的Ca2 部分转运到生长发育中的胚芽和胚根中。随着萌发的继续 ,胚根和胚芽细胞中的Ca2 不会持续增多 ,反而下降     

氯化钠胁迫对罗布麻种子萌发及幼苗生长的影响

用不同浓度的氯化钠溶液处理罗布麻种子,试验结果表明,氯化钠浓度低于0.8%时,可促进罗布麻种子萌芽,高于0.8%小于2.0%时抑制萌芽,超过2.0%时极显著抑制种子萌芽。氯化钠浓度高低均对罗布麻幼苗生长有抑制作用,当浓度大于0.4%时,出叶速度减慢,植株矮化、相对抑制率超过60%,鲜重与对照相比降低了50%以上。     

菹草石芽大小和贮藏温度对萌发及幼苗生长的影响

通过萌发实验探讨了菹草石芽重量和贮藏温度对石芽萌发及幼苗生长的影响。结果表明：成熟的菹草石芽大小不一,按鲜重划分重量等级,各等级石芽数量占总数量的百分比差异很大,重量中等的石芽数量占到80%以上;重量对石芽最终萌发率没有影响,但重量小的石芽萌发时间较早,重量大的石芽虽然萌发较晚但是最终萌生的幼苗数目较多。石芽重量和萌发结束时幼苗数目之间呈显著的线性正相关(p＜0.05);连续去苗过程中,重量大的石芽萌发率和萌发幼苗数保持较高水平;经过贮藏的石芽与未经贮藏的石芽相比,萌发快且萌发整齐。经过15℃贮藏的石芽萌发最早,高温(25℃)和低温(4℃)贮藏均会使石芽最终萌发出的幼苗数目减少,3种温度下贮藏的石芽最终萌发率和幼苗长度无显著差异。     

Transport processes at the plant-fungus interface in mycorrhizal associations: physiological studies

The roots of most plants form symbiotic associations with mycorrhizal fungi. The net flux of nutrients, particularly phosphorus (P), from the soil into the plant is greater in mycorrhizal than in comparable non-mycorrhizal plants. However despite the widespread occurrence of mycorrhizal associations the processes controlling the transfer of solutes between the symbionts are poorly understood. To understand the mechanisms regulating the transfer of solutes information about conditions at the interface between plant and fungus is needed.Measurements of apoplastic and intracellular electrical potential difference in leek roots colonised by mycorrhizal fungi and estimates of cytosolic pH in fungal hyphae are presented. These and the implications for plant/fungal mineral nutrition in vesicular-arbuscular mycorrhizas are discussed.     

光照、温度和土壤水分对孜然芹种子萌发和幼苗生长的影响

连续光照和连续黑暗条件下,孜然芹种子萌发最适宜温度为25℃;16h光照18h黑暗的条件下,萌发最适温度为20℃和25/16℃的日夜变温。种子萌发最适宜土壤含水量为15％。     

Environmental Pollution and Relationship Between Total Antioxidant Capacity and Heavy Metals (Pb,Cd, Zn,Mn, and Fe) in Solanum tuberosum L. and Allium cepa L.

In the natural environment, plants are exposed to different stress factors that are responsible for overproduction of reactive oxygen species. Exposure to heavy metals is one of these factors. The present article highlights the correlation between the effects of bioaccumulation of heavy metals in a highly polluted region as the industrial zone of the Thermo Power Plants “Kosova” in Kosovo on the antioxidant capacity of two selected target species: Solanum tuberosum L. and Allium cepa L. The results show that environmental pollution in the industrial zone of the Thermo Power Plants “Kosova” generates a significant bioaccumulation of heavy metals such as Pb, Cd, Zn, Mn, and Fe. The high concentration of heavy metals leads to an increased production of reactive radical species. The extracts of target plants cultivated in this region display a lower antioxidant capacity than the same plants grown in a control rural area. The Fe bioaccumulation markedly influences the antioxidant capacity of plant samples analyzed.     

Germination of Pistacia vera L. pollen in liquid medium

Summary The osmotic effect of Polyethylene glycol (PEG) has been shown to be sufficient to induce the germination of Pistacia vera L. pollen in liquid medium. The prehydration of the pollen in a saturated atmosphere for approximately 10 h was necessary to obtain maximum in vitro germination. Imbibition of the pollen in water resulted in the rapid leakage of solutes into the medium. These solutes consisted of approximately 50% carbohydrates, of which sucrose (0.65 mol/mg), glucose (0.77 mol/mg) and fructose (0.78 mol/mg) were the major sugars; the remaining 50% comprised proteins with the following major molecular weights 63 kDa, 60 kDa, 59 kDa, 40 kDa, 36 kDa, 35.5 kDa, 31 kDa, other organic matter and minerals.