Phytotoxicity induced by Phragmites australis: an assessment of phenotypic and physiological parameters involved in germination process and growth of receptor plant

This study investigated the possible phytotoxicity induced by Phargmites australis on phenotypic and physiological parameters of recipient plants with identification of major inhibitors in the donor plant. This was achieved using aqueous extracts of different organs and root exudates of P. australis in laboratory and greenhouse experiments with Lactuca sativa as the model test plant. The observed reduced liquid imbibition and altered resource mobilization in seeds of L. sativa, in particular an insufficient carbohydrate supply, demonstrated that the onset of germination might be negatively affected by phytotoxicity. Dose-response studies pointed out that oxidative stress through reactive oxygen species production could potentially cause the observed germination and seedling growth reductions. The osmotic effects by mannitol solution on germination as well as growth and physiology at a level of ?0.57 and ?0.45 bar, respectively, demonstrated that the results from aqueous plant extracts were partially induced by the osmotic potential on and above those levels. Overall, the relative strength of inhibition on measured parameters was the highest in leaf extract, followed by rhizome, root, stem, and inflorescence. Root exudates of P. australis also had negative impacts by reducing germination and growth of plant. High-performance liquid chromatography (HPLC) analysis revealed gallic acid, a potent phytotoxin, as a major compound with an order of leaf >inflorescence>rhizome>root>stem.     

Paenibacillus lentimorbus Enhanced Abiotic Stress Tolerance Through Lateral Root Formation and Phytohormone Regulation

Under the stressed conditions plant growth-promoting rhizobacteria (PGPR) are able to stimulate plant growth through several mechanisms, including antioxidants alleviation, regulation of stress responsive genes and phytohormones etc. Present study is conducted to investigate the impact of Paenibacillus lentimorbus B-30488 inoculation on salinity and drought stress mitigation in Arabidopsis thaliana through modulation in defense enzymes, phyto-hormones and root system architecture associated gene expression profiling. In vitro experiments clearly demonstrated the role of B-30488 in stimulating the root length, branches, lateral root formation and biomass under salinity and drought stress. The inoculation of B-30488 modulated the phytohormones levels to protect the plants from salinity and drought stress. Similarly, defence enzymes were also activated under the stressed conditions, but B-30488 inoculation reduced the antioxidants content during salinity and drought stress as compared to their respective controls. Microscopy results showed decrease in lateral roots hair formation under both stresses and B-30488 inoculation not only mitigate but also enhanced the lateral root formation. Gene expression analysis through real time polymerase chain reaction (RT-PCR) showed modulated expression of several genes related to root development, stress and lateral root formation in B-30488 inoculated seedlings. Results based on the present study, B-30488 is also involved in alteration root architecture, its growth regulation via modulation in phytohormones and genes expression and overall significant improvement in plant growth under stress conditions.

     

土壤镉胁迫对田七体内镉分布及富集特性影响

田七(Panax notoginseng)是我国的一种传统珍贵的草本药用植物,其重金属污染问题已经引起广泛关注。为了分析田七不同部位对镉毒害的响应,明确不同浓度镉污染对田七体内镉分布的基本特征以及不同部位的富集特性,以揭示镉胁迫对田七不同部位的影响机制及富集转移特性。该研究在"田七之乡"广西靖西市田七园以3年生田七为材料,土培条件下以不施镉处理为空白对照,设置6个镉浓度(5、10、20、30、40、50 mg·kg~(-1))梯度,研究了在不同浓度镉胁迫下田七不同部位镉积累特征以及转移特性。结果表明:在不同器官(叶、茎、剪口、须根、主根)随着镉浓度的增加各器官镉的积累量均显著(P0.05)增加,呈现出正相关关系。田七不同部位镉含量的分布特征表现:空白对照下田七各器官镉累积分布表现为须根剪口主根茎叶;当镉浓度为5、10、20、30、40、50 mg·kg~(-1)时,田七镉分布表现为剪口主根须根茎叶;地下部的镉含量显著高于地上部的镉含量;随着镉浓度的增加,无论地下部生物富集系数还是地上部生物富集系数均表现为逐渐降低的趋势。     

Rhizospheric Enterobacter enhanced maize seedling health and growth

Phyto-beneficial effects of rhizobacteria specifically Enterobacter species were evaluated on maize seedling health and growth. Out of the 19 isolates examined, two were remarkable in their phosphate solubilization efficiency (PSE > 70%), chitinase enzyme activity (CEA > 85%) and antifungal activity with evidence of no or low disease expression in maize seedling. The selected isolates (OSR7 and IGGR11) were identified and 16S rDNA revealed both isolates as Enterobacter species. Re-evaluation of both isolates ascertains that their combined effects are more effective on maize seedling than their individual effects. Their combinations completely suppressed pathogenic activity of Fusarium verticillioides on maize seedling with evidence of no disease symptoms. Other treatments significantly (p < 0.05) expressed varied maize seedling diseases such as leaf curl and stem rot. Apart from treatment T2 (maize + pathogen), other treatments most especially their combinations significantly (p < 0.05) enhanced seedling height, stem girth, leaf area, nitrogen and potassium contents. The phyto-beneficial effects of these Enterobacter species suggest that they could be employed as bio-inoculant for maize seedling health and growth.     

Low-density lipoprotein-associated variables and the severity of coronary artery disease: an untreated Chinese cohort study

Abstract

Background and aims: Elevated low-density lipoprotein cholesterol (LDL-C) is causal risk for coronary artery disease (CAD) and LDL-associated variables including LDL-C, apolipoprotein B (apoB), non-high-density lipoprotein cholesterol (non-HDL-C), lipoprotein a [Lp(a)], small dense LDL (sd-LDL), and oxidized LDL (ox-LDL) have been widely used for predicting the risk of CAD. This study was aimed to compare the values of six LDL-related variables for predicting the severity of CAD using untreated patients undergoing coronary angiography (CAG).

Methods: A group of 1977 individuals were consecutively enrolled and divided into CAD (n?=?1151) and non-CAD groups (n?=?826) according to the results of CAG. LDL-C, apoB, non-HDL-C, Lp(a), sd-LDL and ox-LDL were measured, respectively. The numbers of stenotic arteries and Gensini Scores (GS) were used to calculate the severity of CAD and the associations of six variables with the severity of CAD and predicting value of these parameters were simultaneously examined.

Results: CAD patients had significantly higher concentrations of LDL-related variables than non-CAD ones (all p?<?0.05). Importantly, all variables rose with the increase in the severity of CAD. The predicting value of CAD manifested as sd-LDL?>?ox-LDL?>?apoB?>?non-HDL-C?>?LDL-C?>?Lp(a) [area under curve (AUC): sd-LDL 0.641; ox-LDL 0.640; apoB 0.611; non-HDL-C 0.587; LDL-C 0.583; Lp(a) 0.554; respectively]. In multivariate logistic analysis, all variables showed as independent risk factors for the severity of CAD [odds ratio (OR): ox-LDL?>?sd-LDL?>?apoB?>?non-HDL-C?>?LDL-C?>?Lp(a)].

Conclusions: All of LDL-related variables could be useful marker for predicting the severity of CAD but sd-LDL and ox-LDL appeared to litter better. Further study may be needed to validate our results.     

栽培与野生化血丹不同部位中两种化学成分含量分析

为探讨并分析栽培与野生化血丹植株中不同部位中两种化学成分的含量差异,该研究采用超声法提取、高效液相色谱法(HPLC)测定栽培与野生化血丹根、茎、叶、花、混合样等部位中桃叶珊瑚苷和梓醇的含量,并进行比较。结果表明:(1)桃叶珊瑚苷在栽培与野生化血丹植株内均有分布,含量均以根中最高,其在栽培与野生化血丹植株内的含量表现分别为根>叶>混合样>茎>花、根>混合样>茎>花>叶,栽培化血丹不同部位中桃叶珊瑚苷的含量均高于野生化血丹。(2)梓醇在栽培化血丹的茎中未检出,在栽培与野生化血丹其他部位均有分布,含量均以叶中最高,其在栽培与野生化血丹植株内的含量分别表现为叶>花>混合样>根、叶>混合样>茎>花>根,野生化血丹不同部位中梓醇的含量均高于栽培化血丹。(3)桃叶珊瑚苷和梓醇在栽培和野生化血丹植株不同部位中的含量均存在显著差异(P<0.05),栽培与野生同一部位间总体上无显著差异,为该濒危药用植物资源药用部位选择和合理开发利用提供实验参考。     

Genetic variation and productivity of Populus trichocarpa and its hybrids. X. Trait correlations in young black cottonwood from four river valleys in Washington

 A common-garden study of Populus trichocarpa Torr. & Gray was established in spring 1986 with 128 clones collected from sites along two mesic (Hoh and Nisqually) and two xeric (Dungeness and Yakima) river valleys in Washington. Two replicate plantations, one in Puyallup and the other in Wenatchee, Wash., were established with this material. Over 2 years data were taken on stem growth, leaf/crown characters, spring/autumn phenology, and the incidence of Melampsora occidentalis leaf rust. Combining clones from all four sources, correlation/regression analyses were used to examine clonal stability of traits between test sites and trait relationships with stem growth; broad-sense heritabilities (H ²) and genetic correlations revealed the genetic strength of these traits. At Puyallup, many leaf/crown traits predicted stem growth moderately to very well (r ²>0.50), e.g., total leaf area (TLA) to diameter gave an r ² of 0.91 and current-terminal leaf size, of 0.79. Some regressions were quadratic, suggesting a threshold level in a trait (e.g., leaf size) beyond which stem growth levels off. Upper-crown TLA was more closely related to height than TLA of the lower sylleptics, but the reverse was true for diameter. A decline in r ² values from upper to lower crown positions was sharper for correlations of TLAs with height than with diameter. Thus, leaf area allocation seems to differentially affect stem growth. When autumn leaf fall (LF) and rust incidence (R) were regressed with growth, r ² values ranged from 0.58 to 0.71, but those of spring flush (SF) were only 0.10 to 0.12. Early LF and high R, both negatively affecting growth, had a strong geographic component as it occurred mainly on lower-elevation Yakima clones. At Wenatchee, field conditions were harsher and microsites more variable, so trait/growth relationships were weaker. Genetic correlations with growth revealed similar trends as phenotypic analyses. Unlike leaf/crown traits, clonal scores of LF, SF, and R were fairly stable across the two test sites (r ²: 0.58–0.80). These traits also showed strong genetic control (H ²: 0.96–0.98). The trait/growth relationships as well as trait stability within clones have implications for selecting clonal stock in poplar culture and conservation. Received: 23 February 1998 / Accepted: 7 May 1998     

水稻NAM基因家族的全基因组鉴定及表达分析

植物特异性转录因子NAM家族从属于NAC转录因子超家族,在植株生长发育、生理代谢以及应对各种胁迫反应中均发挥重要作用。该研究采用生物信息学方法鉴定水稻基因组中的NAM基因,分析其时空表达模式、亚细胞定位以及蛋白相互作用,并采用实时定量qRT PCR方法分析不同外源激素(如SA、ABA和MeJA)以及非生物胁迫(包括干旱、盐和冷)处理下各NAM基因的表达特征,为进一步探索NAM基因在非生物胁迫中的功能和应激机制以及激素调控途径奠定基础。结果显示：(1)从水稻基因组中共鉴定出48个NAM基因,进化分析将其分为5个亚家族;NAM基因在水稻基因组中存在9对片段复制事件。(2)组织表达分析显示,NAM基因在水稻不同组织及发育时期表现特异性表达,特别是叶鞘、茎和节的生长过程中高表达,且大多数是核定位,并存在多种蛋白互作。(3)实时定量qRT PCR表达分析显示,10个NAM基因在不同组织中均特异表达;大部分NAM基因在盐和干旱胁迫下表达上调,而在冷胁迫下表达降低;SA、ABA和MeJA处理均可显著改变各NAM基因的表达水平。研究表明,NAM基因在水稻生长发育、激素应答和非生物胁迫响应中具有重要作用。     

rol-Gene expression in transgenic aspen (Populus tremula) plants results in accelerated growth and improved stem production index

Stem and trunk growth, axillary bud break and branching habits are extremely important parameters of wood production in forest trees. The possibility of altering tree form by transformation with genes responsible for hormone biosynthesis and/or activity is most attractive. We examined four different phenotypically selected transgenic clones of a model tree –Populus tremula– expressing rol genes from Agrobacterium rhizogenes under their native promoters. Several of the observed phenotypic modifications were correlated with rol-gene expression, including breaking of stem apical dominance which resulted in the development and branching of up to four axillary buds per explant, as compared to a lack of axillary bud break in a uidA (β-glucuronidase-encoding)-transgenic aspen line and control (non-transformed) plants. rol-Transgenic plants also exhibited a higher cumulative stem length and enhanced growth rate, and hence a higher stem production index. During their first and second years in the greenhouse, rol-transgenic aspen plants exhibited enhanced growth and delayed winter dormancy relative to non-transformed plants. Although initially rol-transgenic plants had smaller, wrinkled leaves, these changes were not observed in the 2-year-old plants, which exhibited a phenotypically true-to-type leaf shape. Received: 13 September 1998 / Accepted: 15 April 1999     

Salt stress decreases seedling growth and development but increases quercetin and kaempferol content in Apocynum venetum

• Apocynum venetum L. is a traditional Chinese medicinal herb with great potential to treat angiocardiopathy. Its major medicinal constituents are flavonoids. However, the natural habitats of A. venetum are typically affected by salt stress, which can modify both biomass and accumulation of medicinal compounds.
• In this study, the effects of salt stress on growth and development of A. venetum, accumulation of flavonoids and expression patterns of genes involved in flavonoid biosynthesis were evaluated.
• In general, the growth and development of seedlings (seedling height, root length, leaf length, leaf width and seed germination) were inhibited by salt stress. Unlike typical halophytes, there was no optimal NaCl concentration range that promoted growth and development, but seedlings had an elevated DW/FW ratio under salt stress (induced by irrigation with 50, 100, 200 or 400 mm NaCl). Furthermore, quercetin and kaempferol were significantly accumulated in A. venetum seedlings under salt stress, resulting in a balanced content and reduced FW. Moreover, the expression of AvCHS, AvCHI and AvF3GT was inhibited by salt stress; however, AvF3’H, AvF3H and AvFLS, which are involved in the flavonol synthesis pathway, were up‐regulated under salt stress, consistent with a decrease in total flavonoids and an increase of flavonols (quercetin and kaempferol).
• In summary, cultivation of A. venetum in saline soils appeared to be feasible and improved the medicinal quality of A. venetum (quercetin and kaempferol accumulation under salt stress), thus this species can effectively utilize saline soil resources.

     

Accumulation,distribution and toxicological effects induced by cadmium on the development of mangrove plant <Emphasis Type="Italic">Kandelia candel</Emphasis> (L.)

Accumulation and distribution pattern of cadmium (Cd) and its toxic effect on growth of the mangrove plant of young Kandelia candel seedlings have been examined. This study demonstrated that under high concentration of Cd stress, the total biomass of K. candel decreased 41.57% compare to control (CK). At the end of 90 days exposure to 25 mg/l Cd, the average seedlings stem height and leaf number of the K. candel decreased by 30.54 and 42.68%, respectively. The results showed that K. candel seedlings, under the experimental condition, accumulated higher concentration of Cd in their roots (411.29 ± 3.60 mg/kg) when compared to hypocotyls, stems and leaves. More than 95% of Cd was accumulated mainly in roots. The distribution pattern of Cd concentration in K. candel seedlings was found in the following order: roots > hypocotyls > stems > leaves. Based on the leaf symptoms and morphological change of K. candel seedlings under heavy metal stress, this study showed that Cd is phytotoxic to K. candel.