叶面喷施硒肥对紫花苜蓿富硒降镉效果的影响

为了缓解紫花苜蓿的镉累积并实现富硒目的,探究了不同浓度镉胁迫下叶面喷施硒肥对紫花苜蓿生长特征及富硒降镉特性的影响。以草原三号和中苜一号紫花苜蓿为材料,采用叶面喷施硒肥的方式,在初花期测量紫花苜蓿的株高、生物量并检测根茎叶部位的总硒、硒代蛋氨酸(SeMet)、镉等含量,分析叶面喷施硒肥对紫花苜蓿富硒降镉效果的影响。结果表明,施加外源硒对紫花苜蓿的生长和富硒量均有促进作用,表现为两个品种紫花苜蓿的株高、生物量、总硒和SeMet含量均显著提高,镉含量、镉富集系数、镉转运系数均显著下降。相同喷施硒肥浓度下,低浓度镉污染促进紫花苜蓿的生长,高浓度镉污染则抑制紫花苜蓿的生长。镉浓度为1 mg·kg^(-1)、施硒量为100 mg·kg^(-1)时,紫花苜蓿中硒含量最高、镉含量最低,各组织中总硒、SeMet含量:叶>茎>根,镉含量:茎<叶<根。相同条件下,中苜一号的生物量、总硒、SeMet含量均高于草原三号,镉含量低于草原三号,且在镉浓度为1 mg·kg^(-1)、施硒量为50 mg·kg^(-1)的条件下富硒降镉效果最佳。

植物DNA错配修复系统响应Cd胁迫的研究进展

Cd胁迫下植物细胞内会出现不同形式的DNA损伤(如碱基错配、DNA单/双链断裂和甲基化),DNA损伤会迅速诱导DNA损伤响应(DDR)信号,如ATM、ATR及其下游的信号通路包括细胞周期阻滞、细胞内复制、细胞凋亡以及不同形式的DNA修复途径(如同源重组修复HR、DNA错配修复MMR)。植物细胞DNA MMR系统中的异源二聚体MutSα(MSH2/MSH6)、MutSβ(MSH2/MSH3)、MutSg(MSH2/MSH7)、MutLα(MLH1/PMS1)与有关酶如增殖细胞核抗原(PCNA)、DNA复制因子C(RFC)、DNA核酸外切酶1(EXO1)、单链结合蛋白(RPA)、核酸内切酶FEN1、DNA聚合酶delta(d)和DNA连接酶相互作用,启动DNA MMR反应,从而在感知Cd诱导的DNA损伤、修复DNA损伤、激活细胞周期检验点、确保基因组DNA的稳定性和DNA复制的精确性等方面发挥关键作用。然而,MutS缺失的植物细胞会绕过DNA MMR系统参与的细胞周期阻滞,从而严重影响植物的耐Cd性能。本文重点介绍了植物DNA MMR系统对Cd胁迫的响应以及表观遗传对DNA MMR系统的调控作用机理。

Photochemical behavior of benzo[a]pyrene on soil surfaces under UV light irradiation

The rates of photodegradation and photocatalysis of benzo [a]pyrene （BaP） on soil surfaces under UV light have been studied. Different parameters such as temperature, soil particle sizes, and soil depth responsible for photodegradation, catalyst loads and wavelength of UV irradiation blamed for photocatalysis have been monitored. The results obtained indicated that BaP photodegradation follows pseudo-first-order kinetics. BaP photodegradation was the fastest at 30℃ . The rates of BaP photodegradation at different soil particle size followed the order： less than 1 mm〉less than 0.45 mm〉less than 0.25 mm. When the soil depth increased from 1 mm to 4 ram, the half-life increased from 13.23 d to 17.73 d. The additions of TiO2 or Fe2O3 accelerated the photodegradation of BaP, and the photocatalysis of BaP follows pseudo-first-order kinetics. Changes in catalyst loads of TiO2 （0.5%, 1%, 2%, and 3% （wt）） or Fe203 （2%, 5%, 7%, and 10% （wt）） did not significantly affect the degradation rates. Both BaP photocatalysis in the presence of TiO2 and Fe2O3 were the fastest at 254 nm UV irradiation.

Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area,China

Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area （SZIA） in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils （0-20 cm） and subsoils （20-40 cm） respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hnl2 in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm^2, respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.

不同稳定化材料对镉砷复合污染土壤稳定化修复效果研究

【目的】探究4种稳定化材料(碱性硼泥、酸性硼泥、高岭土和铁改性生物炭)对镉砷复合污染土壤高效同步稳定化修复的效果。【方法】选用碱性硼泥、酸性硼泥、高岭土和铁改性生物炭4种稳定化材料,分别以0.5%、1%、2%、5%的比例添加于镉砷复合污染土壤中进行恒温恒湿培养,研究不同稳定化材料添加对土壤pH值及镉、砷有效态含量的影响。【结果】除碱性硼泥外,其他3种材料均降低了土壤pH值,其中5%铁改性生物炭对土壤pH降低最为显著,处理21 d后土壤p H值下降了3.12个单位。5%铁改性生物炭对砷稳定效果最佳,稳定效率为57.17%,其次是5%高岭土和5%酸性硼泥,稳定效率分别为40.40%和33.37%;5%铁改性生物炭对镉稳定效果也为最佳,稳定效率为35.03%,其次是5%的碱性硼泥,稳定效率为28.20%。【结论】综合考虑土壤镉-砷的同步稳定化修复效果,铁改性生物炭的修复效果明显优于其它3种稳定材料。

玉米镉转运基因ZmNramp1的鉴定及对镉胁迫的响应

NRAMP(natural-resistance-associated macrophage)转运蛋白家族在调控植物吸收、转运重金属镉(Cd)等方面具有重要功能。基于拟南芥、水稻、番茄和山荆子的Nramp1基因的保守序列,设计玉米该基因的兼并引物,克隆测序得到该基因,片段全长314 bp,包含10个外显子,编码104个氨基酸,将其命名为ZmNramp1;对比上述已知植物的Nramp1基因及氨基酸序列后发现,它们具有相同的保守结构域,碱基序列高度相似。生物信息学预测Zm NRAMP1蛋白分子量为11.5 kD,理论等电点为6.92,拥有典型的跨膜螺旋区,属跨膜蛋白。RT-PCR(reversal transcript polymerase chain reaction)结果表明:与对照组相比,玉米幼苗在Cd(50、100μmol·L^(-1)CdCl_(2))胁迫24 h后,ZmNramp1基因在根部的表达显著增加,分别增加了57%、83%,在叶片中的表达亦明显上调;玉米幼苗根中ZmNramp1基因表达与Cd含量呈显著正相关;叶片中二者之间亦为显著的正相关关系。ZmNramp1基因可能参与玉米对Cd的吸收、转运过程,为玉米抗重金属育种提供理论依据和基因资源。

Growth, Cadmium Accumulation and Physiology of Marigold (Tagetes erecta L.) as Affected by Arbuscular Mycorrhizal Fungi

A pot experiment was carried out to study the effects of three arbuscular mycorrhizal fungi (AMF), including Glomus intraradices, Glomus constrictum and Glomus mosseae, on the growth, root colonization and Cd accumulation of marigold (Tagetes erecta L.) at Cd addition levels of 0, 5 and 50 mg kg-1 in soil. The physiological characteristics, such as chlorophyll content, soluble sugar content, soluble protein content and antioxidant enzyme activity, of Tagetes erecta L. were also investigated. The symbiotic relationship between the marigold plant and arbuscular mycorrhizal fungi was well established under Cd stress. The symbiotic relationship was reffected by the better physiobiochemical parameters of the marigold plants inoculated with the three AMF isolates where the colonization rates in the roots were between 34.3% and 88.8%. Compared with the non-inoculated marigold plants, the shoot and root biomass of the inoculated marigold plants increased by 15.2%- 47.5% and 47.8%-130.1%, respectively, and the Cd concentration and accumulation decreased. The chlorophyll and soluble sugar contents in the mycorrhizal marigold plants increased with Cd addition, indicating that AMF inoculation helped the marigold plants to grow by resisting Cd stress. The antioxidant enzymes reacted differently with the three AMF under Cd stress. For plants inoculated with G. constrictum and G. mosseae, the activities of superoxide dismutase (SOD) and catalase (CAT) increased with increasing Cd addition, but peroxidase (POD) activity decreased with increasing Cd addition. For plants inoculated with G. intraradices, three of the antioxidant enzyme activities were significantly decreased at high levels of Cd addition. Overall, the activities of the three antioxidant enzymes in the plants inoculated with AMF were higher than those of the plants without AMF inoculation under Cd stress. Our results support the view that antioxidant enzymes have a great influence on the biomass of plants, and AMF can improve the capability of reactive oxygen species (ROS) scavenging and reduce Cd concentration in plants to alleviate Tagetes erecta L. from Cd stress.

铜、铅离子胁迫对多环芳烃高效降解菌毛霉胞外聚合物特征的影响

微生物胞外聚合物(EPS)在多环芳烃(PAHs)和重金属污染土壤修复领域的作用已有大量研究,但重金属胁迫对PAHs高效降解菌EPS特征的影响机理尚不明确。本文通过使用铜、铅离子作为胁迫源对PAHs高效降解菌毛霉(Muoor mucedo)进行胁迫培养,并对提取的毛霉EPS性质进行表征,阐明在铜、铅离子胁迫下,毛霉EPS特征的变化。结果表明:铜、铅离子浓度从0增加到80 mg·L^(-1),毛霉EPS产生量(TOC)、多糖成分含量(PS)、蛋白质含量(PN)、表面张力、乳化指数和Zeta电位的值(绝对值)逐渐增大,最大值分别达到706.4 mg·L^(-1)、1.035 mg·L^(-1)、0.907 mg·L^(-1)、57.63 m N·m^(-1)、44.5%和-26.21 m V;当铜、铅离子浓度大于80 mg·L^(-1)时,除乳化指数外,EPS产生量、PS、PN、表面张力和Zeta电位值(绝对值)显著降低,同时,Cu^(2+)胁迫下EPS各理化性质的变化比Pb^(2+)胁迫下更加明显;铜、铅离子胁迫对PAHs高效降解菌毛霉EPS产生量、组成成分含量、表面张力、乳化性以及Zeta电位等有促进作用。