Effect of Elemental Sulfur Supply on Cadmium Uptake into Rice Seedlings When Cultivated in Low and Excess Cadmium Soils

Effects of sulfur (S) (0, 30 mg S kg^?1 soil) supply on cadmium (Cd) uptake into rice when cultivated in low-Cd soil [38.8 μg kg^?1 for diethylenetriaminepentaacetic acid (DTPA)–extractable Cd] and in excessive-Cd soil (748.7 μg kg^?1 for DTPA-extractable Cd) were investigated in a combined soil–sand culture experiment. The significant difference in the Cd uptake into rice between –S and +S treatments were observed in relation to soil Cd levels. When rice was exposed to excessive Cd soil, application of S restrained the uptake of Cd into rice, the S supply tended to increase Cd uptake into rice when cultivated in low-Cd soil. The possible mechanisms explaining the interactions among soil Cd level, S supply, and Cd accumulation in rice are proposed. These results suggest that S fertilization may be important for the development approaches to reducing Cd accumulation in rice when cultivated Cd-contaminated soils.     

四川盆地西部漂洗土壤区水体铁元素的分布特征

铁是水质监测的重要指标。为了弄清四川盆地西部漂洗土壤区不同水环境中铁的形态和含量、浅层潜水的季节动态及其形成原因,为该区土、水资源合理利用提供一定参考,于不同时期在四川省名山县漂洗土壤区采集潜水、池塘水、稻田和茶园沟渠地表水、土壤孔隙水及相应的土壤样品,分析了其铁的形态和含量及相应的理化性质。结果表明,从潜水和土壤孔隙水来看,潜水总铁和亚铁含量（分别为0.30、0.08mg·L^-1）均为最低,稻田孔隙水总铁和亚铁含量（分别为2.92、1.13mg·L^-1）均为最高,茶园孔隙水总铁和亚铁含量（3a生以下茶园分别为1.25、0.92mg·L^-1,6a生以上茶园分别为2.66、0.65mg·L^-1）居中;就稻田和茶园的土壤孔隙水与沟渠地表水比较而言,孔隙水总铁和亚铁含量总体上高于沟渠地表水相应的总铁和亚铁含量;潜水总铁和亚铁含量分别变动在0~0.86mg·L^-1和0~0.36mg·L^-1之间,其季节动态在不同区域间存在一定差异,与其所处地形部位及地表径流条件、离居民房屋和畜禽圈舍远近、土壤pH、有机质和铁元素的形态和含量、土地利用方式及作物种植年限、天气状况及水井自身氧化还原电位等条件有关。     

与Fe(III) 共存的Fe(II) 分光光度法测定

Fe(Ⅱ)的含量及变化与土壤和沉积物的氧化还原性质关系密切。当与Fe(Ⅲ)共存时,Fe(Ⅱ)的测定往往受到干扰。本文研究了常用显色剂2,2’-联吡啶和菲洛嗪(Ferrozine)测定土壤Fe(Ⅱ)时存在的问题及解决办法。结果表明,Fe(Ⅲ)可与显色剂作用形成络合物,该络合物对Fe(Ⅱ)测定所用波段的光线具有吸收作用,从而使Fe(Ⅱ)浓度被过高估计。Fe(Ⅲ)对Fe(Ⅱ)测定的干扰程度与其浓度及所选显色剂有关。当以2,2’-联吡啶为显色剂时,单位浓度Fe(Ⅲ)(1.0 mg/L)将导致Fe(II)的测定值比实际值高0.012 mg/L;而当菲洛嗪为显色剂时,单位浓度Fe(Ⅲ)引起的Fe(Ⅱ)高估值在0.010～0.032 mg/L之间。F-能够抑制Fe(Ⅲ)-显色剂络合物的形成。当F-的加入量超过Fe(Ⅲ)的4倍时,F-能有效地消除Fe(Ⅲ)的干扰。实际样品的测定结果表明,改进的Fe(Ⅱ)分光光度法能够满足土壤及沉积物中Fe(II)的准确测定。     

几种胡敏酸还原容量的表征与比较

还原容量(RC)是衡量胡敏酸(HA)还原特性的重要指标。采用饱和H2振荡法和土壤溶液法对HA分别进行化学和微生物预处理,分别以硝酸铁(Fe(NO3)3)、柠檬酸铁(FeCit)作电子受体,测定了三种HA(上海巨枫SH,天津光复TJ,缙云山JY)的本底还原容量(NRC),化学还原容量(CRC),微生物还原容量(MRC)。对不同电子受体条件下、不同初始状态和不同种类的胡敏酸的RC进行比较。结果表明：三种HA中,以缙云山土壤提取的胡敏酸RC值最高,还原容量最大,分别为20.21?0.26mmolc mol-1C (NRC)、26.02?1.12mmolc mol-1C (CRC)和29.29?1.56mmolc mol-1C (MRC)。两种电子受体中,采用Fe(NO3)3得到的RC明显高于在FeCit条件下。另外,溶液态HA的RC明显高于固态。由此证明胡敏酸还原容量是一个相对量;其容量大小不仅和自身结构、性质有关,也受到HA初始形态和不同电子受体的影响。对比三个还原容量指标发现CRC和MRC显著大于NRC,而CRC和MRC之间无明确大小关系,因此用CRC来表征HA被微生物还原后的还原容量(MRC)还需作进一步验证。     

Effects of Broomrape Parasitism on Sunflower Plants: Growth,Development, and Mineral Nutrition

Sunflower broomrape (Orobanche cumana Wallr.) is a parasitic plant that infects sunflower (Helianthus annuus L.) plants. In this work, sunflower plants were grown under greenhouse conditions in pots with the substrate infested or non-infested with broomrape seeds. At different numbers of days after sowing, plant height, internode lengths, number of leaves, head diameter, mineral composition of leaves, and potassium (K) concentration in stem were measured. The negative effects of broomrape parasitism were assessed from 57 d after sowing, when broomrape started to emerge. Parasitized plants exhibited lower shoot dry weight, height, and head diameter than control plants. The reduction in internode lengths was associated with a decrease in the gradient of K concentration from basal to apical stem. The mineral composition of leaves was also affected in parasitized plants. The concentrations of calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) in leaves of parasitized plants were lower than those of the control plants, while there were few differences for K, phosphorus (P), iron (Fe), and copper (Cu). The effects of parasitism are discussed in relation to their competition for resources and to perturbations of the host physiology such as hormonal and water balance.     

Soil fertility ‐ crop genotype associations and interactions 1

This paper discusses the opportunities to combine the efforts of plant geneticists and soil scientists to develop crop varieties adapted to the existing soil conditions and techniques used for production. Such research should result in improved varieties for the best as well as poorest of soil and production situations.     

Studies on post‐reddening changes in amino acid content leaves of hirsutum cotton and its control with chemicals

The aspartic acid,tyrosine and serine contents of leaves were found reduced in prematurely reddened leaves of hirsutum cotton (Gossypium hirsutum) as compared to healthy green leaves. Amino acids other than those listed above were higher in the affected red leaves. Amino acids threonine and proline increased 63.7 and 2.3 fold over green leaves respectively. Chemical sprays not only maintained the levels of various amino acids at par with green leaf but tended to increase the concentration above the levels obtained in normally found green leaf. However, threonine level was dropped in treated leaves as compared to partly affected red leaf and chemical sprays significantly reduced the leaf reddening when it was sprayed before flowering. It can be suggested that the leaf reddening can possibly be arrested by monitoring threonine content in leaves of hirsutum cotton ov. L‐147.     

华北平原典型农区农地细碎化对村级农田林网的影响--以河北省曲周县为例

本研究以河北省曲周县农地细碎化的杏园村、西魏村和农地规模经营的东刘庄村为例,采用实地测量和问卷调查的方法,探明农地细碎化对村级农田防护林的影响及其根源。结果表明,农地细碎化对村级农田林网结构和配置造成破坏。农地细碎化的林网网格增大,主带距是华北平原区推荐值的2.70倍。农地细碎化林网树种单一,配置不合理。杏园村和西魏村约53.8%的干道北侧无林木,干道北侧林带林木数量平均比南侧显著减少60.8%;其紧邻农田行树木密度为0~26株·50m-1,比次邻行的数量显著减少25.8%(P0.05),比东刘庄减少47.3%。据林带面积与林木数量关系的拟合曲线,东刘庄村林木最高密度为23.2株·100m-2,比其余两村高56.5%。多数农户反对田边地头栽树,经营林网技术匮乏。人多地少矛盾是林网毁坏的深层原因,林木胁地是其直接原因,农地细碎化激化了这些矛盾。土地整理规划是解决现状的根本途径,同时不可忽视社会教育和管理。     

施用生物炭和零价铁粉对土壤中镉形态变化的影响

通过施用生物碳和还原性铁粉,研究其对土壤镉形态变化的影响.结果表明:生物碳或还原性铁粉单施及二者配施均极显著改变土壤镉形态.其中生物炭、还原性铁粉二者配施效果优于单施;单施生物炭主要对交换态镉的降低效果显著,同时对碳酸盐结合态镉、有机结合态镉及残渣态镉的形成起显著作用;而单施还原性铁粉对铁锰氧化结合态镉的形成起显著作用.另外,镉的活性指数从4.36降到0.97,不同形态镉含量的最大变化为,交换态镉比例从81.04％降到49.16％;碳酸盐结合态镉从9.44％升到17.93％;铁锰氧化结合态镉从2.95％升到10.88％;有机结合态镉从2.66％升到11.33％;残渣态镉从3.91％升到14.42％.在16个处理中,I3B2(铁粉0.045 g/kg土和生物炭3.0 g/kg土)处理为最佳组合.     

发酵脱氢产氢过程对微生物铁还原的影响

发酵型微生物是铁还原菌中的主要类群,但其发酵产氢过程对铁还原的作用尚不清楚,为此采用接种水稻土浸提液混合培养的方法对微生物分别利用葡萄糖、丙酮酸盐和乳酸盐为碳源时,Fe（Ⅲ）还原过程中脱氢酶活性变化、培养体系pH、氢气分压及铁还原特征进行分析,探讨了发酵微生物脱氢产氢过程与微生物Fe（Ⅲ）还原的内在关系。结果表明：2种水稻土浸提液中的微生物均能够以葡萄糖为优势碳源进行脱氢、产氢及还原氧化铁,Fe（OH）,可以诱导脱氢酶的产生,利用葡萄糖时脱氢酶活性在厌氧培养的4-6d出现最大峰值,利用丙酮酸盐和乳酸盐时脱氢酶活性出现峰值的时间分别为培养的15d和21-22d,脱氢酶活性出现峰值的时间与最大铁还原速率Vmax显著负相关、与最大反应速率对应的时间zk存在显著正相关关系。脱氢产氢过程中产生的H＋导致培养体系pH的变化是影响铁还原过程的主要原因,培养体系pH与体系氢气分压及Fe（Ⅱ）累积量呈极显著负相关。微生物利用不同碳源产氢时,利用葡萄糖的产氢能力最高,丙酮酸盐次之,乳酸盐最低。Fe（OH）3的加入增加了氢气的消耗量,培养体系氢气分压与Fe（Ⅱ）累积量存在极显著正相关关系。