Impact of drought stress on growth and quality of miscanthus for biofuel production

Miscanthus has a high potential as a biomass feedstock for biofuel production. Drought tolerance is an important breeding goal in miscanthus as water deficit is a common abiotic stress and crop irrigation is in most cases uneconomical. Drought may not only severely reduce biomass yields, but also affect biomass quality for biofuel production as cell wall remodeling is a common plant response to abiotic stresses. The quality and plant weight of 50 diverse miscanthus genotypes were evaluated under control and drought conditions (28 days no water) in a glasshouse experiment. Overall, drought treatment decreased plant weight by 45%. Drought tolerance – as defined by maintenance of plant weight – varied extensively among the tested miscanthus genotypes and ranged from 30% to 110%. Biomass composition was drastically altered due to drought stress, with large reductions in cell wall and cellulose content and a substantial increase in hemicellulosic polysaccharides. Stress had only a small effect on lignin content. Cell wall structural rigidity was also affected by drought conditions; substantially higher cellulose conversion rates were observed upon enzymatic saccharification of drought‐treated samples with respect to controls. Both cell wall composition and the extent of cell wall plasticity under drought varied extensively among all genotypes, but only weak correlations were found with the level of drought tolerance, suggesting their independent genetic control. High drought tolerance and biomass quality can thus potentially be advanced simultaneously. The extensive genotypic variation found for most traits in the evaluated miscanthus germplasm provides ample scope for breeding of drought‐tolerant varieties that are able to produce substantial yields of high‐quality biomass under water deficit conditions. The higher degradability of drought‐treated samples makes miscanthus an interesting crop for the production of second‐generation biofuels in marginal soils.     

“How” and “what” matters: Sampling method affects biodiversity estimates of reef fishes

Understanding changes in biodiversity requires the implementation of monitoring programs encompassing different dimensions of biodiversity through varying sampling techniques. In this work, fish assemblages associated with the “outer” and “inner” sides of four marinas, two at the Canary Islands and two at southern Portugal, were investigated using three complementary sampling techniques: underwater visual censuses (UVCs), baited cameras (BCs), and fish traps (FTs). We firstly investigated the complementarity of these sampling methods to describe species composition. Then, we investigated differences in taxonomic (TD), phylogenetic (PD) and functional diversity (FD) between sides of the marinas according to each sampling method. Finally, we explored the applicability/reproducibility of each sampling technique to characterize fish assemblages according to these metrics of diversity. UVCs and BCs provided complementary information, in terms of the number and abundances of species, while FTs sampled a particular assemblage. Patterns of TD, PD, and FD between sides of the marinas varied depending on the sampling method. UVC was the most cost‐efficient technique, in terms of personnel hours, and it is recommended for local studies. However, for large‐scale studies, BCs are recommended, as it covers greater spatio‐temporal scales by a lower cost. Our study highlights the need to implement complementary sampling techniques to monitor ecological change, at various dimensions of biodiversity. The results presented here will be useful for optimizing future monitoring programs.     

不同地下水矿化度对柽柳光合特征及树干液流的影响

为揭示柽柳(Tamarix chinensis)光合能力及耗水特征对地下水矿化度的响应规律, 以黄河三角洲建群种——柽柳3年生植株为研究对象, 在1.2 m的潜水水位下, 模拟设置淡水、微咸水、咸水和盐水4种不同的地下水矿化度, 测定柽柳叶片光合-光响应、蒸腾速率和树干液流的日变化。结果表明: 地下水矿化度通过影响土壤盐分可显著影响柽柳光合特性及耗水性能。随地下水矿化度升高, 柽柳叶片净光合速率(P_n)、最大P_n、蒸腾速率、气孔导度、表观量子效率和暗呼吸速率均先升高后降低, 而水分利用效率(WUE)持续降低。淡水、微咸水和盐水处理下, 柽柳P_n光响应平均值分别比咸水处理降低44.1%、15.1%和62.6%; 微咸水、咸水和盐水处理下, 柽柳WUE光响应平均值分别比淡水处理降低25.0%、29.2%和41.7%。随地下水矿化度升高, 柽柳叶片光饱和点先升高后降低, 而光补偿点持续升高, 光照生态幅变窄, 光能利用率变低。淡水和盐水处理下, 柽柳P_n下降分别是非气孔限制和气孔限制引起的。柽柳树干液流速率随地下水矿化度升高而先升高后降低, 咸水处理下树干液流速率日变幅最大, 日液流量最高。淡水、微咸水和盐水处理下日液流速率平均值分别比咸水处理降低61.8%、13.1%和41.9%。咸水矿化度下柽柳有较高的光合特性, 在蒸腾耗水较严重的情况下可实现高效生理用水, 适宜柽柳较好地生长。     

Improving crop nutrient efficiency through root architecture modifications

Improving crop nutrient ef ficiency becomes an essential consideration for environmentally friendly and sustainable agriculture. Plant growth and development is dependent on 17 essential nutrient elements,among them,nitrogen(N) and phosphorus(P) are the two most important mineral nutrients. Hence it is not surprising that low N and/or low P availability in soils severely constrains crop growth and productivity,and thereby have become high priority targets for improving nutrient ef ficiency in crops. Root exploration largely determines the ability of plants to acquire mineral nutrients from soils. Therefore,root architecture,the 3-dimensional con figuration of the plant's root system in the soil,is of great importance for improving crop nutrient ef ficiency. Furthermore,the symbiotic associations between host plants and arbuscular mycorrhiza fungi/rhizobial bacteria,are additional important strategies to enhance nutrient acquisition. In this review,we summarize the recent advances in the current understanding of crop species control of root architecture alterations in response to nutrient availability and root/microbe symbioses,through gene or QTL regulation,which results in enhanced nutrient acquisition.     

Malatesta转基因研究:引证分析及相关证据

发表多篇以转基因农产品饲喂动物而导致健康损害论文的维罗纳大学(University of Verona)学者Manuela Malatesta,是国际上采用实验方法研究转基因生物安全领域有影响力的学者之一。通过对美国Web of Science数据平台全部论文的检索,重点分析了其所发表的10篇转基因毒理学论文的研究内容、研究方法与结论,并追踪其研究的相关证据及学术界对其研究的评价,在此基础上,分析该研究方法与结论的可靠性。研究发现,Malatesta所发表转基因存在安全隐患的10篇研究论文,由于其研究材料及方法上所存在的问题除了个别存在明显错误的论文无法重现而被学术界所否定外,其余论文均被后续采用规范研究方法的同类研究所推翻。     

Leaf nutrient dynamics and nutrient resorption: a comparison between larch plantations and adjacent secondary forests in Northeast China

Aims Conversion of secondary forests to pure larch plantations is a common management practice driven by the increasing demand for timber production in Northeast China, resulting in a reduction in soil nutrient availability after a certain number of years following conversion. Nutrient resorption prior to leaf senescence was related to soil fertility, an important nutrient conservation strategy for plants, being especially significant in nutrient-poor habitats. However, the seasonal dynamics of leaf nutrients and nutrient resorption in response to secondary forest conversion to larch plantations is not well understood.Methods A comparative experiment between larch plantations (Larix spp.) and adjacent secondary forests (dominant tree species including Quercus mongolica, Acer mono, Juglans mandshurica and Fraxinus rhynchophylla) was conducted. We examined the variations in leaf nutrient (macronutrients: N, P, K, Ca and Mg; micronutrients: Cu and Zn) concentrations of these tree species during the growing season from May to October in 2013. Nutrient resorption efficiency and proficiency were compared between Larix spp. and the broadleaved species in the secondary forests.Important findings Results show that the seasonal variation of nutrient concentrations in leaves generally exhibited two trends, one was a downward trend for N, P, K, Cu and Zn, and another was an upward trend for Ca and Mg. The variations in foliar nutrient concentrations were mainly controlled by the developmental stage of leaves rather than by tree species. Resorption of the observed seven elements varied among the five tree species during leaf senescence. Nutrient resorption efficiency varied 6–75% of N, P, K, Mg, Cu and Zn, while Ca was not retranslocated in the senescing leaves of all species, and Mg was not retranslocated in Larix spp. Generally, Larix spp. tended to be more efficient and proficient (higher than 6–30% and 2–271% of nutrient resorption efficiency and resorption proficiency, respectively) in resorbing nutrients than the broadleaved species in the secondary forests, indicating that larch plantations had higher leaf nutrient resorption and thus nutrient use efficiency. Compared with Larix spp., more nutrients would remain in the leaf litter of the secondary forests, indicating an advantage of secondary forests in sustaining soil fertility. In contrast, the larch plantation would reuse internal nutrients rather than lose nutrients with litter fall and thus produce a positive feedback to soil nutrient availability. In summary, our results suggest that conversion from secondary forests to pure larch plantations would alter nutrient cycling through a plant-mediated pathway.     

Effects of transgenic soybean on growth and phosphorus acquisition in mixed culture system

Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean‐soybean mixed cultures were employed to illuminate P acquisition among plants in mixed stands of transgenic and wild‐type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild‐type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean‐maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.     

小鼠精原干细胞不同转染方法效率的比较

本研究采用腺病毒感染、慢病毒感染、脂质体转染和电穿孔转化方法将含有绿色荧光蛋白（GFP）的质粒转入经过差异贴壁法初步分离纯化的小鼠精原干细胞(SSCs)中,转染48 h后通过流式细胞仪检测GFP阳性细胞比例比较4种方法在体外转染精原干细胞的效率.结果显示,脂质体转染效率最高仅为8.64%,不能满足对精原干细胞进一步实验的要求;电穿孔法效率最高达到25.27%,但转化后细胞大量死亡;腺病毒转染细胞的效率达到了32.4%;慢病毒转染效率最高,达到74.25%. 因此,慢病毒转染法是体外转染小鼠精原干细胞的有效方法.     

大豆油体与EGF融合基因的克隆及其在红花种子中的表达

目的：旨在建立一种在红花油体中表达EGF的转基因植物的方法。方法：通过PCR技术把大豆油体基因（DDoil）与EGF构建成融合基因,克隆至植物表达载体pCAMBIA1390R中,构建成植物表达载体p1390Do-EGF,然后转化进农杆菌 LBA4404 中用于侵染红花外植体,通过甘露糖筛选培养基培养可获得红花转化苗。通过PCR、实时荧光相对定量RT-PCR、SDS-PAGE和Western blot分析目的基因的表达情况,通过MTT法检测EGF的促细胞增殖活性。结果：PCR结果显示,红花叶片中能检测到EGF基因;实时荧光相对定量RT-PCR结果显示,在红花种子中EGF能成功实现转录;SDS-PAGE和Western blot检测证明,在转基因红花种子中能有效表达出EGF,并具有其原有的免疫原性,MTT法实验结果表明EGF具有促进balb/c 3T3细胞增殖的生物活性。结论：大豆油体和EGF融合基因已经成功转化进红花细胞的基因组中,并实现了EGF外源蛋白在红花种子油体中的表达,为EGF蛋白的产业化生产探讨了一种新的生产途径。     

Capitalizing on multi-element interactions through bal-anced nutrition——A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.