Impact of soil salinity on the plant-growth – promoting and biological control abilities of root associated bacteria

The effectiveness of plant growth – promoting bacteria is variable under different biotic and abiotic conditions. Abiotic factors may negatively affect the beneficial properties and efficiency of the introduced PGPR inoculants. The aim of this study was to evaluate the effect of plant growth – promoting rhizobacteria on plant growth and on the control of foot and root rot of tomatoes caused by Fusarium solani under different soil salinity conditions. Among the five tested strains, only Pseudomonas chlororaphis TSAU13, and Pseudomonas extremorientalis TSAU20 were able to stimulate plant growth and act as biological controls of foot and root rot disease of tomato. The soil salinity did not negatively affect the beneficial impacts of these strains, as they were able to colonize and survive on the roots of tomato plants under both saline and non-saline soil conditions. The improved plant height and fruit yield of tomato was also observed for plants inoculated with P. extremorientalis TSAU20. Our results indicated that, saline condition is not crucial factor in obtaining good performance with respect to the plant growth stimulating and biocontrol abilities of PGPR strains. The bacterial inoculant also enhanced antioxidant enzymes activities thereby preventing ROS induced oxidative damage in plants, and the proline concentrations in plant tissue that play an important role in plant stress tolerance.     

Studies on the salt tolerance of some flower crops grown under glass

Summary The salt sensitivity of carnations, gerberas, anthuriums, chrysanthemums and hippeastrums was studied in an investigation. The crops were grown in basins filled with soil and irrigated with the aid of low level sprinklers. Two different cultivars of each crop were included in the experiments. The crops were irrigated with water containing different levels of salts. The EC of the irrigation water (EC_w) ranged between 0.2 and 3.9 mS.cm^–1 at 25°C.The salt applications had a deleterious effect on the development of all the flower crops used in the investigation. Carnations and chrysanthemums proved to be the least sensitive. Gerberas and hippeastrums showed a medium sensitivity and anthuriums proved to be the most salt sensitive. The latter crop also showed a specific sensitivity to sodium chloride.The salinity threshold values were low for most crops,i.e. EC_w<0.6. Slightly higher values were found for carnations only. The salinity decrease values of EC_w showed very wide variations and ranged from 6 to 34%. A method is proposed for the conversion of EC_w values into EC values for the saturation extract (EC_e) with the aid of the soil analytical results.The results of tissue analyses showed that the sodium and chloride contents in particular were affected by the salt applications. The effects of the salt applications on the uptake of the major nutrient elements varied from crop to crop.     

含ACC脱氨酶的根际细菌提高植物抗盐性的研究进展

盐胁迫是抑制植物生长的主要非生物因素之一,高浓度的盐分不利于植物体的生长和发育,严重时会导致植物细胞及植物体死亡.已有大量实验结果显示含ACC脱氨酶的根际细菌可以缓解高盐对植物的危害.ACC脱氨酶可以降解乙烯的直接前体1-氨基环丙烷-1-羧酸(ACC),从而降低胁迫乙烯的合成量.胁迫乙烯是阻碍植物生长的主要原因.首先介...     

Plant Growth-Promoting Effects of Diazotrophs in the Rhizosphere

Because of their ability to transform atmospheric N₂ into ammonia that can be used by the plant, researchers were originally very optimistic about the potential of associative diazotrophic bacteria to promote the growth of many cereals and grasses. However, multiple inoculation experiments during recent decades failed to show a substantial contribution of Biological Nitrogen Fixation (BNF) to plant growth in most cases. It is now clear that associative diazotrophs exert their positive effects on plant growth directly or indirectly through (a combination of) different mechanisms. Apart from fixing N₂, diazotrophs can affect plant growth directly by the synthesis of phytohormones and vitamins, inhibition of plant ethylene synthesis, improved nutrient uptake, enhanced stress resistance, solubilization of inorganic phosphate and mineralization of organic phosphate. Indirectly, diazotrophs are able to decrease or prevent the deleterious effects of pathogenic microorganisms, mostly through the synthesis of antibiotics and/or fungicidal compounds, through competition for nutrients (for instance, by siderophore production) or by the induction of systemic resistance to pathogens. In addition, they can affect the plant indirectly by interacting with other beneficial microorganisms, for example, Azospirillum increasing nodulation of legumes by rhizobia. The further elucidation of the different mechanisms involved will help to make associative diazotrophs a valuable partner in future agriculture.     

黄土高原旱地长期施用微肥对冬小麦产量及氮磷养分吸收的影响

以长达18年的微量元素肥料定位试验为背景,研究了长期施用微肥对小麦产量及氮磷养分吸收量的影响。结果表明,在施NP肥的基础上施Zn、B、Mn可显著提高小麦生物学产量,较NP KH2PO4分别提高6％以上;施Zn、B可显著提高小麦籽粒产量,较NP增产分别为5．5％和6．0％,较NP KH2PO4分别增产8．4％和8．9％;施Cu使小麦吸氮量提高3．1％,吸磷量提高7．7％,较NP KH2PO4吸氮量、吸磷量分别提高6．0％和5．5％;施Zn使小麦吸氮量提高4．1％,吸磷量提高2．5％,分别较NP KH2PO4处理吸氮量、吸磷量分别提高8．0％和6．9％;同时,施Zn、Mn、Cu肥较NP KH2P04更有利于籽粒对氮素的吸收。     

Some important physiological selection criteria for salt tolerance in plants

Undoubtedly, plant breeders have made a significant achievement in the past few years, improving salinity tolerance in a number of potential crops using artificial selection and conventional breeding approaches, although molecular biology approaches are currently being intensively pursued for achieving this goal. However, most of the selection procedures used so far, were based merely on differences in agronomic characters. Agronomic characters represent the combined genetic and environmental effects on plant growth, and include the integration of the physiological phenomena conferring salinity tolerance. In fact, physiological criteria are able to supply more reliable information than agronomic characters. Although there are large numbers of reports in the literature mainly dealing with water relations, photosynthesis, and accumulation of various inorganic ions and organic metabolites in individual crops, there is little information available on the use of these attributes as selection criteria for improving salt tolerance through selection and breeding programs. In this review, the major adaptive components of salt tolerance such as osmotic adjustment, photosynthesis, water relations and ion relations are reviewed. In view of the complexity of salt tolerance and its great variation at intra-specific and inter-specific levels, it is difficult to identify single criteria, which could be used as effective selection targets. Rather it is most meaningful if physiological and biochemical indicators for individual species are determined rather than generic indicators.     

氮胁迫对水曲柳幼苗养分吸收、利用和生物量分配的影响

树木受到环境胁迫时发生形态和生理上的改变,以便获取对其生长发育限制最严重的资源．在东北林区凋落物因受温度影响分解速度和有机物矿质化过程缓慢,森林树木常受到氮营养胁迫．通过温室栽培试验,对氮胁迫下水曲柳幼苗生长的生理学和形态学指标进行了研究．结果表明,在氮胁迫下,水曲柳幼苗的净氮吸收速率和净磷吸收速率都会减少,但在生长前期氮利用效率和磷利用效率高于氮供给充足(8mmol·L^-1)和过量(16mmol·L^-1)时的氮利用效率和磷利用效率．当氮供给浓度不足时,叶重比减少,而特定叶面积和根重比增加．相对生长速率随氮供给浓度增加而增加．在氮胁迫下净同化速率下降,导致总生物量下降．在幼苗生长前期,水曲柳幼苗处于氮胁迫时根／茎比显著大于氮供给充足或过量时的根／茎比。而在生长后期。根／茎比没有显著差别．     

中国生态卫生建设的潜力、挑战与对策

立足于社会一经济.自然复合生态系统结构与功能框架,以中国农村卫生系统为重点,在分析卫生系统现状水平的基础上,结合地理布局和社会经济发展状况,划分了中国发展生态卫生的6个分区,并研究了各分区现状及其4类卫生系统的人口分布.缺乏基本卫生设施的地区是未来中国发展生态卫生的最大潜力地区,这些地区包括了严重缺乏投入资金的4 682万农村人口,主要集中在中西部和西南部地区,占67.8%.若在该区域推广生态卫生,可能产生社会、经济及环境效益如下:带动新兴产业,增加5～10万的直接就业机会;降低疾病感染率;回收沼气56万m3;卫生厕所投入控制在可接受的600～750元·户-1;促进生态农业循环;降低污染物排放、保障生态安全.文章还探讨了中国生态卫生的分区发展对策和系统瓶颈.     

Time-courses of size-fractionated phosphate uptake: are larger cells better competitors for pulses of phosphate than smaller cells?

Summary Time-course experiments of phosphate uptake by size-fractionated phytoplankton were conducted in oligotrophic Kennedy and Sproat Lakes. The objective was to determine if large phytoplankton obtained more phosphate than smaller cells, when the nutrient was present at higher concentrations. Studies at Kennedy Lake revealed that uptake rates in the 0.2–3.0 m fraction were very sensitive to the time they were exposed to elevated concentrations; rates determined over the 60–120 min interval were less than 30% of those recorded over the 0–60 min interval. In contrast, there was little difference in uptake rates over these intervals for cells>3.0 m. At Sproat Lake phosphate incorporation into the two size fractions was followed after the aerial fertilization of the lake with inorganic nutrients. Following nutrient addition the proportion of phosphate entering the>3.0 m size fraction increased from ca. 35% to ca. 85%. Despite these observations, it is doubtful that larger cells are able to sequester enough phosphate from pulses to realize the same specific growth rates as their smaller counterparts.     

耕作播种方式对稻茬小麦生长和养分吸收利用的影响

2016—2018年,在四川省广汉市分析了深旋耕播种(DRT)、浅旋耕播种(SRT)和免耕带旋播种(NT)3种耕播方式对稻茬小麦生长和养分吸收利用的影响。结果表明:与DRT相比,SRT和NT处理提高了小麦分蘖、成穗能力。2016—2017年,处理间产量无显著差异;2017—2018年,NT处理产量显著高于DRT,增幅10.9%。处理间干物质积累的差异主要在苗期。NT处理下植株对氮的吸收量高于DRT,平均增幅9.9%,而氮收获指数DRT高于NT;各处理植株磷吸收量差异不显著;NT处理对钾的吸收量显著高于DRT。与传统的深旋耕播种方式相比,免耕带旋播种技术是提高稻茬小麦产量和养分吸收的有效途径。     

Bt毒素在三种矿物表面的吸附与解吸

研究了Bt库斯塔克亚种(kurstaki）毒素（65 kDa）在高岭土、针铁矿和氧化硅表面的吸附和解吸特性.结果表明：在磷酸盐缓冲体系（pH 8）中,3种矿物的等温吸附曲线均符合Langmuir方程（R²>0.9661）,它们对Bt毒素的吸附顺序为：针铁矿﹥高岭土﹥二氧化硅.矿物对Bt毒素的吸附1 h就基本达到了吸附平衡.在pH 6～8范围内,针铁矿、高岭土和二氧化硅对Bt毒素的吸附量随pH值的升高而降低.10 ℃～50 ℃范围内,针铁矿和氧化硅对Bt毒素吸附量随温度升高有所下降（8.39％和47.06％）,高岭土对Bt毒素吸附则略有升高（5.91％）.红外光谱分析显示,Bt毒素被矿物吸附后结构仅有微小变化.被矿物吸附的Bt毒素不易被去离子水解吸,水洗3次总解吸率为28.48%～42.04%.