根系分泌物与根际微生物相互作用研究综述

对几种主要根系分泌物与根际微生物之间的相互作用关系和影响机理的研究进行了综述，同时提出了今后在根系分泌物及根际微生态方面需要深入研究的几个问题。     

沙打旺与柳枝稷单、混播种苗期水分利用和根冠生长的比较

在室内生长箱内盆栽沙打旺和柳枝稷的苗期生长阶段进行高土壤水分 (黄绵土土壤田间持水量FC的 80 % )和低土壤水分 (5 0 ?)处理 ,比较二者单、混播种植下水分利用与根冠生长差异 ,以探讨黄土高原半干旱丘陵区牧草植物的合理种植方式 .结果表明 :在水分利用方面 ,低水处理下混播使沙打旺和柳枝稷叶片瞬时水分利用效率均较单播提高 ,低水处理后混播群体水分利用效率也显著比单播柳枝稷增大 .在根冠生长方面 ,混播促进了柳枝稷地上部分植株高度生长 ,并使地下部分分配比重增大 ,根系绝对长度缩短 ;混播后沙打旺的植株高度降低 ,根系绝对长度增加 ,但干物质分配比重减小 .低水处理后 ,沙打旺和柳枝稷混播下的根冠生长趋向于资源的充分合理利用 ,表现在混播群体的根系生长有利于充分利用土壤深层水和表层来水 ,混播后地上部分高度的生长特征变化利于对光的利用 .因此 ,在水分和养分条件相对较差坡地占较大比例的半干旱黄土丘陵地区 ,采用沙打旺和柳枝稷混播种植相比各自单播利于促进苗期生长与提高土壤水分利用率 .图 2表 2参 10     

煤矸石复垦中的氮素积累途径

进行了煤矸石上种植接菌种草及加覆盖物种植牧草的盆栽和小区试验。结果表明，接菌种植可以显著提高植物的固氮酶活性和结瘤率，改善煤矸石的氮素贫瘠状况，促进牧草根系和地上部分的生长和煤矸石的进一步风化；这些结果在施氮量中等区w(N)=15g/100kg更为明显。同时在煤矸石上加薄层覆盖物种植豆科植物，对其氮素的积累提高和生物性状的同样具有明显的促进作用，并以黄土覆盖效果更佳。这些结果为解决煤矸石复垦中氮素缺乏的问题提供了有效途径。表3参4     

Hg2+胁迫下玉米生理生态变化的研究

通过砂培实验,研究汞胁迫下玉米的生理生态指标包括叶绿素含量、根系活力、游离脯氨酸含量的变化.结果表明,汞对玉米的胁迫是浓度和时间双重因子的作用在低汞浓度、短时间内,叶绿素含量、根系活力及游离脯氨酸含量均有上升的趋势;在高汞浓度、长时间内,各生理指标均严重下降.各生理指标对汞的敏感度略有差异游离脯氨酸含量>根系活力>叶绿素含量;其中脯氨酸含量可以作为汞污染的一个监测指标.     

空气CO2体积分数升高对稻麦根系活力及其VA菌根侵染率的影响

利用无锡市安镇的FACE研究平台，在施常规氮量和低氮量的条件下，研究CO2体积分数升高对稻麦轮作系统水稻和小麦根系活力及其VA菌根侵染率的影响。结果表明，在常氮和低氮条件下，FACE处理对小麦和水稻根系活力都有促进作用，并使小麦VA菌根侵染率在拔节期和孕穗期有增加趋势，小麦根系活力和VA菌根侵染率有正相关关系。施N量不足对作物根系生长和活力有一定影响，可以被CO2体积分数升高的影响所补偿。     

油料作物对土壤老化残留DDT的吸收积累

油料作物对亲脂性DDT的吸收富集能力是否会更强是一个值得研究的问题。采用DDT老化残留土壤,温室盆栽油料作物花生(Arachishypogaea),大豆(Glycinemax)和芝麻(Sesamumindicum)。果实成熟后将植株分成根、茎、果壳和果仁四部分,GC-ECD测定各部位中的DDT浓度。研究了油料作物对土壤老化残留DDT的吸收积累情况,结果表明,∑DDT在三种作物不同部位中的浓度顺序都是:根>茎>果壳>果仁。含油量高的花生果仁和芝麻果仁中∑DDT浓度都明显高于大豆果仁的∑DDT浓度,这种差异有可能是由果仁含油量的差异造成的。单株植物吸收积累∑DDT的总量顺序为:花生>芝麻>大豆。花生、大豆和芝麻三种作物的根和茎的生物富集系数都比较高,特别是花生的,说明这三种油料作物根部从土壤中吸收积累老化残留DDT的能力以及从根部向茎部运输DDT的能力都是相当强的。     

大豆根系分泌物和根细胞壁对难溶性磷的活化

探讨了不同磷效率大豆品种根系细胞壁和根分泌物对难溶性铝磷的活化与吸收能力。结果表明，砂培条件下，磷高效品种(巴西10号)对难溶性铝磷的吸收显著高于磷低效品种(本地2号)。铝磷处理条件下，根系总表面积巴西10号是本地2号的131％，而钾磷处理二者没有明显差异。根系细胞壁对铝磷的活化表明，大豆苗期根系细胞壁对铝磷的活化量显著高于成熟期。苗期、成熟期巴西10号对铝磷的活化量为本地2号的119％、176％。不同栽培方式根系细胞壁对铝磷的活化量表现为水培大于砂培，水培条件下两个大豆基因型对铝磷的活化量没有差异。不同生育时期、栽培方式根分泌物对铝磷的活化量表现为，成熟期大于苗期，砂培大于水培。巴西10号根分泌物对铝磷的活化量比本地2号分别高出69．3％(成熟期)和40．1％(砂培)。上述研究结果表明，大豆根分泌物和根细胞壁对难溶性铝磷的溶解具有促进作用，有利于大豆对铝磷的吸收。     

Phytotoxicity assessment of phenanthrene, pyrene and their mixtures by a soil-based seedling emergence test

Seedling emergence tests were conducted in a meadow brown soil using five plant species ( i. e., Chinese cabbage, green onion, tomato, turnip and wheat) to determine the phytotoxicity of phenanthrene, pyrene and their mixtures. The soil was amended with up to 1000mg/kg soil of phenanthrene or 600 mg/kg soil of pyrene. Seedling emergence and root growth were measured. The results indicated that root elongation was more sensitive than seedling emergence. Root length decreased with increasing phenanthrene or pyrene concentrations(p≤0.05). Phenanthrene was more phytotoxic than pyrene. The lowest observable adverse effect concentration(LOAEC) was 10mg/kg for phenanthrene when tested with green onion, and 50mg/kg for pyrene when tested with wheat. Among the five species, wheat was found to be the most sensitive. When amended jointly at or below their respective LOAEC, phenanthrene and pyrene produced a synergistic toxic effect.     

The Influence of Mycorrhiza on Uranium and Phosphorus Uptake by Barley Plants from a Field-contaminated Soil (7 pp)

Background Recent studies indicated that arbuscular mycorrhizal fungi (AMF) play important roles in plant accumulation of uranium (U) from contaminated environments, but the impacts of fertilization practices on functioning of the symbiotic associations, which are crucial factors influencing plant nutrition and growth responses to mycorrhiza, have rarely been considered. Materials and Methods In a greenhouse experiment, a bald root barley mutant (brb) together with the wild type (wt) were used to test the role of root hairs and AMF in uranium (U) uptake by host plants from a U contaminated soil. Nil, 20 and 60 mg KH2PO4-P kg–1 soil were included to investigate the influences of phosphorus (P) fertilization on plant growth and accumulation of U. Results Dry matter yield of barley plants increased with increasing P additions and wt produced significantly higher dry weight than brb. Mycorrhiza markedly improved dry matter yield of both genotypes grown at nil P, whereas only brb responded positively to mycorrhiza at 20 mg P kg-1. At the highest P level, mycorrhiza resulted in growth depressions in both genotypes, except for the roots of wt. In general, plant P concentrations increased markedly with increasing P additions and in response to mycorrhiza. Mycorrhiza and P additions had no significant effects on shoot U concentrations. However, root U concentrations in both genotypes were significantly increased by mycorrhiza. On the other hand, shoot U contents increased with increasing P levels, while 20 mg P kg-1 stimulated, but 60 mg P kg-1 marginally affected the U accumulation in roots. Root length specific U uptake was moderately enhanced both by root hairs and strongly enhanced by mycorrhiza. Moreover, non-inoculated plants generally had higher shoot-root ratios of U content than the corresponding inoculated controls. Conclusion Our study shows that AMF and root hairs improves not only P acquisition but also the root uptake of U, and mycorrhiza generally decreases U translocation from plant root to shoot. Hence, mycorrhiza is of potential use in the phytostabilization of U contaminated environments. Perspectives The complex impacts of P on U accumulation by barley plants suggested that U behavior in mycorrhizosphere and translocation along the soil-fungi-plant continuum as affected by fertilization practices deserve extensive studies for optimizing the function of mycorrhizal associations for phytoremediation purposes.     

利用集合均方根卡尔曼滤波反演重庆地区SO2源排放

传统的"自下而上"清单方法估算的排放清单,其数据的准确性和时效性存在较大局限.基于集合均方根卡尔曼滤波的源清单反演方法,结合WRF-CMAQ（天气研究和预报模式-公共多尺度空气质量模型）被用于对以清华大学编制的2010年MEIC（中国多尺度排放清单模型）排放清单为基础制作的重庆地区SO₂排放源进行反演试验以解决准确性和时效性问题,试验时间段为2014年10月15-31日,重庆主城17个环境空气质量国控监测点ρ（SO₂）小时观测资料用于反演及检验.结果表明:该方法能够反演重庆地区SO₂源排放量,随着反演次数增加,基于反演排放源预报的ρ（SO₂）预报误差持续减小,反演4次后预报误差达到比较低的稳定的水平,其均方根误差均低于20 μg/m3. 5次反演后SO₂源排放量用于2014年10月24-29日每天起始预报,其预报的站点、时间平均的均方根误差从100~400 μg/m3降至30 μg/m3以下.反演中应用局地化尺度减少集合取样误差影响,54与81 km两个局地化尺度反演结果对预报改善效果相当,表明主要影响重庆主城ρ（SO₂）的源排放位于主城及周边地区,也说明内源排放对重庆主城ρ（SO₂）起主要影响.反演后面源排放量主城区降幅约为30 kg/（d·km2）,周边地区减少10~20 kg/（d·km2）,主城区部分SO₂点源排放量降幅约为25 kg/（d·km2）,说明2010年MEIC排放清单高估了试验时段重庆地区的SO₂排放.