土壤重金属胁迫与植物相关miRNA的研究进展

重金属污染是指由于人类对矿山过度开采、金属冶炼与加工及其它化工操作,造成的铅(Pb)、汞(Hg)、镉(Cd)、铬(Cr)等重金属以各种形式进入生态环境中,在其中留存、积累和迁移而造成的生态污染,土壤重金属污染的治理已成为目前环保关注的焦点。植物在长期进化过程中形成了根系富集、细胞壁束缚、跨膜转运等多种应对重金属胁迫的应答机制。microRNA(miRNA)是一类调控基因表达的重要小分子RNA,通过调控靶基因的表达而参与植物的生长发育、胁迫应答等生理代谢活动,它们同样在植物应答重金属胁迫过程中发挥重要作用。该研究对土壤中重金属污染现状进行了综述,并阐述了重金属胁迫条件下相关miRNA表达调控情况,以期为更好地研究植物miRNA应答重金属胁迫的调控机制提供参考依据。     

瘤胃液对全株甜高粱青贮质量的影响

甜高粱是一种重要的能源作物,为实现长时间贮存并提升糖化效率,该研究分析了瘤胃液不同添加量对全株甜高粱青贮品质和酶解糖化效果的影响.设置R1、R3、R5和R7共4个瘤胃液处理组(添加量依序分别为1、3、5和7 mL/100 g原料)和1个对照组(CK,等量蒸馏水),考察了瘤胃液不同添加量对全株甜高粱青贮过程中有机组分、发...     

8种绢蒿属植物幼苗抗氧化保护系统研究

在土培条件下研究了民勤绢蒿Seriphidium minchiinense、针裂叶绢蒿S. sublessingianum、西北绢蒿S. nitrosum、伊犁绢蒿S. transiliense、博洛塔绢蒿S. borotalense、蛔蒿S. cinum、沙湾绢蒿S. sawanense和新疆绢蒿S. kaschgaricum等8种绢蒿属植物幼苗抗氧化保护系统随生育期的变化.结果表明:8种绢蒿属植物幼苗随生育期后延,叶片MDA、可溶性糖、POD活性先升后降,可溶性蛋白表现出"升-降-升"趋势,SOD和CAT活性分别出现持续下降和持续上升趋势.8种绢蒿幼苗保护酶活性、MDA、可溶性糖和可溶性蛋白含量存在差异,针裂叶绢蒿MDA含量最高,西北绢蒿MDA含量最低.MDA与可溶性糖极显著负相关,与SOD显著负相关.不同指标变化趋势说明在幼苗生长前期主要依靠CAT、POD和非酶性保护系统抵抗不良环境,而后期抵抗作用主要源于SOD和非酶性保护系统.8种绢蒿幼苗中,抗逆性强的有西北绢蒿、民勤绢蒿、博洛塔绢蒿、沙湾绢蒿和蛔蒿,抗逆性较强的有新疆绢蒿和伊犁绢蒿,抗逆性最弱的是针裂叶绢蒿.种间抗逆性的差异是它们对各自生长环境适应的结果.     

基于高光谱的冬油菜植株氮素积累量监测模型

为无损和定量研究高光谱技术在冬油菜植株氮素积累量(PNA,plant nitrogen accumulation)时空变化监测的适宜性及准确性,该文以两年田间氮肥水平试验为基础,采用单变量线性和非线性回归方法,建立基于特征光谱参数的冬油菜P NA高光谱估算模型。结果表明,采用比值光谱的方法可显著提高冬油菜冠层光谱反射率与PNA间的相关性,其最佳的波段组合为1 259 nm与492 nm处光谱反射率比值(R1259/R492),决定系数R2为0.85。高光谱参数间,以比值植被指数(RVI-5)、归一化光谱指数(NDSI)、线性内插法红边位置(REIP)、三角植被指数(TVI)、742 nm处一阶微分光谱值(FD742)和红边面积(SDR)等光谱参数与PNA相关性较好(平均R2和标准误SE分别为0.69和42.70),且以FD742表现最优(R2=0.79,SE=35.66)。精度分析结果显示,以光谱参数R1259/R492和FD742为自变量的指数方程模型作为高光谱监测油菜PNA的最佳模型,各生育期Noise Equivalent(NE)均较低且表现稳定,同时模型估测精度较高,R2分别为0.98和0.98,相对均方根误差RRMSE分别为0.73和0.72,相对误差MRE分别为14.42%和10.31%。该方法为快捷和精确评估冬油菜PNA提供了新的研究思路。     

Electron transfer capacity of soil dissolved organic matter and its potential impact on soil respiration

Purpose

Soil dissolved organic matter (DOM) as the labile fraction of soil organic carbon (SOC) is able to facilitate biogeochemical redox reactions effecting soil respiration and carbon sequestration. In this study, we took soil samples from 20 sites differing in land use (forest and agriculture) to investigate the electron transfer capacity of soil DOM and its potential relationship with soil respiration.

Materials and methods

DOM was extracted from 20 soil samples representing different land uses: forest (nos. 1–12) and agriculture (nos. 13–20) in Guangdong Province, China. Chronoamperometry was employed to quantify the electron transfer capacity (ETC) of the DOM, including electron acceptor capacity (EAC) and electron donor capacity (EDC), by applying fixed positive or negative potentials to a working electrode in a conventional three-electrode cell. The reversibility of electron accepting from or donating to DOM was measured by applying switchable potentials to the working electrode in the electrochemical system with the multiple-step potential technique. Carbon dioxide produced by soil respiration was measured with a gas chromatograph.

Results and discussion

Forest soil DOM samples showed higher ETC and electron reversible rate (ERR) than agricultural soil DOM samples, which may be indicative of higher humification rate and microbial activity in forest soils. The average soil respiration of forest soil (nos. 1–12) and agricultural soil (nos. 13–10) was 26.34 and 18.58 mg C g^?1 SOC, respectively. Both EDC and EAC of soil DOM had close relationship with soil respiration (p?<?0.01). The results implied that soil respiration might be accelerated by the electroactive moieties contained in soil DOM, which serve as electron shuttles and facilitate electron transfer reactions in soil respiration and SOC mineralization.

Conclusions

DOM of forest soils showed higher ETC and ERR than DOM of agricultural soils. As soil represents one of the largest reservoirs of organic carbon, soil respiration affects C cycle and subsequently CO₂ concentration in the atmosphere. As one of the important characteristics of soil DOM related to soil respiration, ETC has a significant impact on greenhouse gas emission and soil carbon sequestration but has not been paid attention to.     

黄河三角洲盐碱地刺槐混交林对土壤脲酶活性的影响

以黄河三角洲盐碱地26年生刺槐＋臭椿混交林（RA）、刺槐＋白榆混交林（RU）和刺槐＋白蜡混交林（RF）为研究对象,以刺槐纯林（RP）和无林地（CK）为对照,研究刺槐混交林对土壤脲酶活性的影响。结果表明：1）同一林分中,土壤脲酶活性随土层深度的增加而减小;2）不同林分之间表现为刺槐混交林〉刺槐纯林〉无林地,RP、RU、RF、RA的脲酶活性分别是CK的4．02、4．74、5．08和5．01倍;3）在影响土壤脲酶活性的土壤因子方面,刺槐混交林较其纯林表现为降低了土壤密度、pH值和含盐量,增大了总孔隙度,增强了蓄水性能,增加了全氮、碱解氮和有机质的质量分数,增加了细菌和固氮菌的数量;4）总孔隙度、细菌、固氮菌、全N和有机质等土壤因子对刺槐混交林土壤脲酶活性的影响较大,建议用这些土壤因子作为评价刺槐混交林土壤脲酶活性的主要指标。     

Enzymatic dehydrogenative polymerization of urushiols in fresh exudates from the lacquer tree, Rhus vernicifera DC

Fresh exudates from the lacquer tree, Rhus vernicifera DC, were extracted with acetone and the solution was chromatographed to isolate monomer, dimer, trimer, and oligomer fractions of urushiols. Constituents of the monomeric and dimeric fractions were then identified by two-dimensional (2D) 1H-13C heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond coherence (HMBC) NMR spectroscopic techniques. The results showed that the monomeric fraction contained 3-[8'Z,11'E,13'Z-pentadecatrienyl]catechol (1), 3-[8'Z,11'Z,14'-pentadecatrienyl]catechol (2), and 3-pentadecanyl]catechol (3), which was verified by HPLC analysis. The dimeric fraction contained 8'-(3' ',4' '-dihydroxy-5' '-alkenyl)phenyl-3-[9'E,11'E,13'Z-pentadecatrienyl]catechol (4), 14'-(3' ',4' '-dihydroxy-5' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadecatrienyl]catechol (5), 2-hydroxyl-3- or -6-alkenylphenyl ethyl ether (6), 14'-(3' ',4' '-dihydroxy-2' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadeca-trienyl]catechol (7), 15'-(2' '-hydroxy-3' '- or -6' '-alkenyl)phenyloxy-3-[8'Z,11'Z,13'E)-pentadecatrienyl]catechol (8), 14'-(2' ',3' '-dihydroxy-4' '-alkenyl)phenyl-3-[8'Z,10'E,12'E-pentadecantrienyl]catechol (9), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-4,3'-biphenyl (10), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-4,4'-biphenyl (11), 1,1',2,2'-tetrahydroxy-6,6'-dialkenyl-5,4'-biphenyl (12), and 1,2,1'-trihydroxy-6,6'-dialkenyldibenzofuran (13) as constituents. In addition, dimeric ethers and peroxides, such as compounds 14 and 15, were produced by autoxidation of monomeric urushiols in atmospheric air. The possible reaction mechanisms for the dehydrogenative polymerization of urushiols by Rhus laccase present in the fresh raw exudates under the atmospheric oxygen are discussed on the basis of structures identified. This is of primary importance because the use of the urushi exudates as coating materials does not involve organic solvents and is an environmentally friendly process.     

Enhanced Bacillus thuringiensis Production from Sewage Sludge with Alkaline and Ultrasonic Pretreatments

Sewage sludge is a cost-effective media for the production of Bacillus thuringiensis (Bt) based biopesticides. To enhance the entomotoxicity of the fermentation broth, pretreatments of sewage sludge by alkali and ultrasonic were applied in this study. Effects of alkaline and ultrasonic pretreatments on the soluble COD (SCOD) and total COD (TCOD) were evaluated by altering the alkali addition dose and the ultrasonic specific energy. Suitable pretreatment conditions were optimized with 5 g l^?1 sodium hydroxide (NaOH) for alkaline treatment and 1.2?×?10⁵ kJ kg^?1 of total solid for ultrasonic treatment. Fermentations of raw and pretreated sludge for biopesticides were carried out in a bench scale fermentor. Results revealed that both pretreatments were effective for Bt growth and metabolism. Higher viable cells (VC) and viable spores (VS) counts, δ-endotoxin yields and entomotoxicity were achieved in the pretreated sludge. The enhancement was attributed to more available nutrients and better oxygen transfer. Moreover, ultrasonic pretreated sludge was superior to alkaline pretreated sludge for δ-endotoxin production and entomotoxicity owing to its higher soluble C/N ratio and finer particles.     

农业土壤表面不平度和测量与分析

农业土壤表面不平度与土壤风蚀、行走装置的相互作用和田间土壤含水量测定分布图等方面具有极其重要的作用.本文利用激光式不平度测试仪测定犁耕耕地地面、圆盘耙地地面和驱动耙耙地地面的不平度,测定地面不平度沿着三个方向进行,即平行于耕作方向、倾斜于耕作方向和垂直于耕作方向.对每一种地面不平度的RMS值、相关长度和自相关函数进行了分析,结果表明对于短的地块,可用单一尺度来表征地表不平度的特征,地表不平度特征属于指数相关函数,RMS高度和自相关长度具有明显的相关性.对于长的地块,平整的农业地表不平度具有分形性或多尺度性,其自相关函数是一种分形过程.