Evaluation of Salt Tolerance and Its Relationship with Carbon Isotope Discrimination and Physiological Parameters of Barley Genotypes

Soil management through the cultivation of salt-tolerant plants is a practical approach to combat soil salinization. In this study, salt tolerance of 35 barley (Hordeum vulgare L.) genotypes was tested at four salinity levels (0, 100, 200, and 300 mM NaCl in Hoagland nutrient solution) at two growth stages (germination and vegetative). The relationship between salinity tolerance and carbon isotope discrimination (CID) was also accessed. Results of the study carried out under laboratory conditions showed that a negative linear relationship was observed between salt concentration and germination as well as other growth parameters. Some genotypes showed good salt tolerance at germination but failed to survive at seedling stage. However, five genotypes, namely, Jau-83, Pk-30109, Pk-30118, 57/2D, and Akermanns Bavaria showed better tolerance to salinity (200 mM) both at germination and at vegetative growth stage. The salt tolerance of these barley genotypes was significantly correlated with minimum decrease in K⁺:Na⁺ ratio in plant tissue with increase in the root zone salinity. However, the case was reversed in sensitive genotypes. CID was decreased linearly with increase in root zone salinity. However, salt-tolerant genotypes maintained their turgor by osmotic adjustment and by minimum increase in diffusive resistance and showed minimum reduction in CID (Δ) with gradual increase in rooting medium salt concentration. Results suggested that the tolerant genotypes make osmotic adjustments by selective uptake of K⁺ and by maintaining a higher K⁺:Na⁺ ratio in leaves. Moreover, CID technique can also be good criteria for screening of salt-tolerant germplasm.     

碳氮稳定同位素检测能力的验证——2013年实验室间比对分析结果的汇总

稳定性同位素示踪技术,特别是碳、氮稳定性同位素已广泛地应用于农业化学、地球化学和环境化学。碳、氮同位素比值的质谱检测结果直接关系到示踪试验的可靠性。在目前缺乏富集碳、氮同位素的标准物质的条件下,通过实验室间的比对可以验证各实验室对碳、氮同位素比值检测能力、检测结果的准确性和可比性。我所在2013年组织和实施了一次由全国14个单位的检测实验室共17台仪器参加的农业、生态和环境样品中碳氮百分含量及其稳定性同位素比值的实验室间比对。我所制备了多种被检测的样品,有含碳氮的化学肥料、土壤和植物样品;在稳定性同位素富集度上,有自然丰度的和不同富集程度的同位素样品。除固体样品外,还有3种不同丰度的N2O和CO2气体样品。在进行检测结果的统计和评价时,采用Z比分衡量各实验室检测结果的可信度。本文汇总了2013年实验室间比对的结果。     

Soil N Losses by Denitrification Evaluated Using the 15N Tracer Method

Molecular nitrogen (N₂) and nitrous oxide (N₂O) generated by denitrification increase N losses in the soil–plant system. This study aimed to quantify N₂ and N₂O from potassium nitrate (K¹⁵NO₃) applied to soils with different textures and moisture contents in the absence and presence of a source of carbon (C) using the ¹⁵N tracer method. In the three soils used (sandy texture (ST), sandy clay loam texture (SCLT), and clayey texture (CT)), three moisture contents were evaluated (40%, 60%, and 80% of the water holding capacity (WHC)) with (D⁺) and without (D^?) dextrose added. The treatments received 100 mg N kg^?1 (KNO₃ with 23.24 atom% ¹⁵N). N₂ emissions occurred in all of the treatments, but N₂O emissions only occurred in the D⁺ treatment, showing increases with increasing moisture content. SCLT with 80% WHC in the D⁺ treatment exhibited the highest accumulated N emission (48.26 mg kg^?1). The ¹⁵N balance suggested trapping of the gases in the soil.     

施肥对土壤及黄瓜中稳定性氮同位素丰度的影响

研究不同肥料配施对土壤、黄瓜及其叶片中稳定性氮同位素丰度(1δ5N‰)及硝酸盐和硝酸还原酶活性的影响。结果表明,随着配施有机肥比例的降低,黄瓜中1δ5N呈现先低后高再低的趋势;各处理单施化肥初期时黄瓜中1δ5N与有机肥60%和40%配施处理间差异显著(P0.05),中期时与有机肥60%、40%配施处理及对照间的差异显著(P0.05),末期时与有机肥60%配施处理间有差异(P0.05),与其他不同配施时差异不显著(P0.05);相同处理的不同采摘时期黄瓜中1δ5N差异不显著(P0.05)。不同处理时叶片与黄瓜间的1δ5N呈正相关(r=0.9836),其1δ5N主要受不同肥料配施处理的影响。随着有机肥比例的降低,黄瓜中硝酸盐含量逐渐降低,与黄瓜中1δ5N间的线性相关性差(r=0.6568);而叶片中硝酸还原酶活性逐渐提高,其中对照处理、100%、80%和60%有机肥处理时与叶片中δ15N丰度呈正相关(r=0.9187);60%、40%、20%有机肥和100%化肥处理时与叶片中1δ5N呈负相关(r=-0.9773)。总体来看,可以初步利用1δ5N作为标记来区分有机肥和化肥种植的黄瓜,但需要进一步研究1δ5N在作物中的分馏和分布规律。     

大气CH_4中碳稳定同位素组成的PreCon-GC/C-IRMS系统测定

利用预浓缩装置-气相色谱,燃烧-同位素比值质谱仪(PreCon-GC/C-IRMS)联用系统,建立了就采样、浓缩和在线质谱分析大气CH_4中稳定碳同位素组成的测定方法.通过多组试验对比,分析并讨论了利用PreCon-GC/C-IRMS联用技术测定大气CH_4中碳稳定同位素比值的试验条件、系统线性、稳定性及准确度和精密度等.结果表明,在本研究方法条件下,当离子流强度在1.0～20 V时,系统线性良好(斜率S=0.04%./V),在4.0～15 V内其线性(斜率S=0.03%./V)优于总体线性;系统测量稳定性可靠,δ~(13)C值的测定结果的S.D<0.3‰,最大偏差<0.5‰,回收率达99.99%,准确度和精度均符合分析与研究要求.利用该系统对室内和室外草坪地空气中CH_4的碳稳定同位素组成做初步测试,其碳同位素的平均值分别为-31.358‰和-33.085%.,且相同地点区域空气中CH_4的δ~(13)C值,在1d内和不同日期间的变化均在0.5‰以内,重现性良好.     

Towards a better understanding of carbon flow in the rhizosphere: a time-dependent approach using carbon-14

 Controversies exist in interpreting rhizosphere C flow obtained by different ¹⁴CO₂ labelling methods. However, there is a need for the standardisation of methods in order to be able to compare values obtained for different plants, different stages of development and different habitats. Perennial bromegrass (Bromus erectus Huds) grown in soils of different fertility was exposed to a ¹⁴CO₂ atmosphere for different periods of time: 1 h, 298 h and 78 days. The evolution of ¹⁴CO₂ in the soil was measured during and after labelling. The ¹⁴C contents of plant and rhizosphere compartments were then estimated. The time-sequence of the rate of ¹⁴CO₂ evolution after 1 h of labelling, indicated a maximum after around 20 h, followed by an exponential decrease. When expressed as a percentage of net ¹⁴C assimilation, root-soil respiration accounted for 14% and 18% in the nutrient-poor and nutrient-rich soils, respectively. Integration of the hourly values over several days showed that the dynamics of the evolution rate were similar for the 298-h and 78-day experiments, thus indicating that rhizosphere C flow was dominated by newly assimilated C. This was confirmed by the proportions of below-ground ¹⁴C, measured for roots, respiration and soil, which were not significantly affected by the labelling regime. The differences were, however, found to be significant between the two types of soils. The conclusion was that the conditions for plant growth during labelling were more important than the length of time of labelling, and that this explained the discrepancies in the literature-cited values. A succession of short-term ¹⁴C labelling of plants at different development stages followed by an allocation period of about 1 week is proposed to give a reliable estimation of the dynamics of C flow in the rhizosphere. Received: 7 June 1999     

稳定性氮同位素技术研究太湖梅梁湾区域营养盐差异

稳定同位素技术通常用于指示外源输入对环境的影响,采用该技术分析了太湖北部不同湖区悬浮颗粒有机物和浮游动物的碳氮稳定同位素比值的差异。结果表明,不同粒径的悬浮颗粒有机物和浮游动物稳定同位素比值存在显著的季节变化,夏季普遍高于冬季,其中δ13C高3.19‰~7.21‰,δ15N高4.20‰~9.36‰。各有机物δ13C不能有效区分各湖区的环境差异,而δ15N在各湖区存在显著差异。δ15N聚类分析显示,河口区由于受外源输入的影响,其δ15N显著低于其他湖区,单独聚为一类,而交汇处和湖心区影响较小,同河口区存在显著差异。整体来讲,总颗粒有机物和浮游动物δ15N同水体TP浓度呈显著正相关,同总溶解性无机氮浓度、铵根离子浓度呈显著负相关。可见,太湖北部悬浮颗粒有机物和浮游动物δ15N受环境营养盐差异的影响强烈,悬浮颗粒有机物δ15N可以作为指示湖区区域差异的有效指标。     

稳定同位素在植物水分来源及利用效率研究中的应用

介绍了稳定氢、氧、碳同位素技术在定量区分植物水分来源及利用效率研究中的应用。以往大量研究结果表明,由于植物根系在吸收水分过程中没有发生同位素分馏,所以通过比较和分析植物木质部水分及其可利用水源的氢氧同位素δ值,就可以定量判断植物的水源;植物在光合作用过程中会产生碳同位素的分馏,从而使得植物叶片中的碳同位素组成能够成为指示植物水分利用效率的一个间接指标,是目前研究植物叶片长期水分利用效率的最佳方法;稳定同位素技术作为安全的示踪剂,有助于人类了解植物的生理生态功能,随着该技术的不断完善和研究的不断深入,同位素技术将会在生态学研究的许多领域得到广泛的应用。     

地表水硝酸盐的氮·氧稳定同位素研究进展

氮污染特别是地表水硝酸盐污染已经成为人们普遍关注的环境问题。为有效控制地表水硝酸盐污染,最根本的方法就是确定硝酸盐污染源,减少硝酸盐的输入。不同来源的硝酸盐具有不同的氮、氧同位素组成,利用硝酸盐稳定氮、氧同位素对硝酸盐污染源进行示踪已经得到广泛应用。在分析不同来源硝酸盐δ15N与δ18O值的组成特征及其影响因素的基础上,对不同土地利用类型流域条件下同位素技术的应用方法和研究进展进行综述,并对目前研究存在的问题和未来的发展进行总结。     

新常态下山东省粮食生产面临的挑战及对策

山东省是我国粮食生产大省,对其粮食生产状况进行研究,对确保国家粮食安全具有重要意义。该研究分析了山东省粮食生产发展现状,指出当前山东省粮食生产取得了综合生产能力稳步提高、粮田基础设施逐步完善、科技支撑能力不断增强、机械化作业水平大幅度提高等成效,但在稳定粮食面积、改善农田基础设施条件、提高耕地质量、调动农民种粮积极性等方面面临挑战。结合山东省在优良品种和生产技术、加工转化能力、中低产田改造潜力等方面的优势,提出了强化基本农田保护、加强基础设施建设、抓好粮食高产创建、提高科技支撑能力、搞好资源集约利用、培育新型经营主体、加大政策保障力度等对策建议,推动全省粮食生产稳定发展。