Copper and Zinc Competitive Adsorption: Desorption in Calcareous Soils

The behavior in competitive adsorption-desorption reactions of Cu and Zn was studied in four calcareous soils. Cu and Zn were added to the soil by Cu, Zn, and Cu+Zn sulfate solutions in a CaSO4 background. Soil sorption of these cations was described by equilibrium isotherms that fitted either Freundlich- or Langmuir type equations, although Cu desorption data fitted only Freundlich isotherms. Cu and Zn competition was quantified by distribution coefficients, Kd, relating cation distribution between soil and solute and by the competitive Langmuir equation. The competitive Langmuir equation was the better suited to describe the Cu-Zn competitive adsorption in these soils. Distribution coefficients presented lower values when both cations were present, decreasing when the Cu and Zn concentration in solution increased (decreasing soil affinity for these cations), thereby increasing their mobility through the soil. However, the distribution coefficient of specifically adsorbed Cu in equilibrium with cations extracted by a Mg (NO) solution increased with Cu concentration. Cu adsorption was more depres 3 se 2 d by Zn than Zn adsorption by Cu. The different behavior of Cu and Zn seems dependent on the percentage Ca (CO) and, to a lesser degree, on Cu and Zn organic matter complexes, free iro 3 n 2 content, and surface precipitation on oxides and carbonates.     

塔克拉玛干沙漠新月形沙丘不同部位的粒度特征

通过对塔克拉玛干沙漠东经84°沿线,北纬38°50′～40°50′之间复合型沙垄垄间平地新月形沙丘的粒度筛析资料分析表明:沙丘沙以极细沙和细沙为主,二者含量达80～90%以上。平均粒径3.34φ。落沙坡脚最细,往迎风坡脚越来越粗。分选程度以沙丘脊部最好,向两坡逐渐较差。沙丘上沙子搬运以跃移为主,该组分含量占90%左右。粗截点2～3φ、细截点4φ左右。地面滚动组分平均含量<6%,悬移组分平均含量<3%。丘间地平均粒径2.94φ,分选也较沙丘差。作为对照,文中还论述了纵向沙垄的粒度特征。     

不同小麦品种籽粒中脂肪酸组分含量及其相关性研究

为了明确小麦品种的脂肪酸及其组分的含量,选取97个小麦品种(系),利用气相色谱仪对其全麦粉脂肪酸组分进行了测定,并初步分析了部分品种(系)的脂肪酸组分含量的分布及其相关性,结果表明,总脂肪酸平均含量为1.91％,其中棕榈酸(C16∶0)、硬脂酸(C18∶0)、油酸(C18∶1)、亚油酸(C18∶2)和亚麻酸(C18∶3)的平均含量依次为0.37％、0.02％、0.27％、1.17％和0.08％,分别占总脂肪酸组成的20％、1％、14％、61％和4％.不饱和脂肪酸(油酸、亚油酸和亚麻酸)在总脂肪酸中所占的比例达到79％;总脂肪酸及其组分含量呈现中间多、两头少的正态分布,变异幅度较大;总脂肪酸含量与棕榈酸、硬脂酸、油酸和亚油酸4种组分含量相关极显著,而与亚麻酸的含量无显著相关.     

A Contribution Towards a Revision of the Aquatic Oligochaeta of Africa

Gene products of nine loci were examined by horizontal starch-gel electrophoresis in five samples of black mussels, Choromytilus meridionalis, from the south-western Cape coast. Allelic frequency variation for four polymorphic proteins suggests no racial differences between west and south coast populations. Mean heterozygosity (H) showed a non-significant increase from south to west coast populations. The duration of the pelagic larval stage and currents may both contribute to long-distance larval recruitment, although gene flow between neighbouring populations may be more important.     

高产冬种马铃薯的钾素吸收、积累、分配特征研究

通过氮磷钾基肥、追肥比例田间试验,研究冬种马铃薯对钾素吸收、积累和分配规律.结果表明:叶片中钾素含量在齐苗后65 d左右出现一个峰值后降低;在茎中,在齐苗后15 d和45 d出现双峰曲线;块茎中,在齐苗后35 d左右达到最大,然后下降.湿冷年型,每生产1 000kg块茎需要吸收钾素(K)5.82 kg;干凉年型,每生产1 000kg块茎需要吸收钾素(K)7.28 kg.钾素在叶片中的分配率在齐苗后5d左右最高,70％以上的钾素分配到叶片,此后逐渐下降至10％左右;茎中的分配比率在齐苗后15d左右最高,达到30％左右,此后逐渐下降并保持在10％左右;块茎中,钾素分配比率逐渐增加,到生育末期,有80％左右的钾素分配到块茎中.     

铝毒对植物生物效应的研究进展

综述近年来植物铝毒的研究进展.从植物体对铝的吸收、分布、生长发育和生理指标等方面阐述铝对植物的影响,为今后研究植物抗铝毒机制提供依据.     

我国苦苣苔科植物研究进展

我国苦苣苔科植物资源丰富,但受环境、人为及其自身特点的影响,园艺化栽培较少,甚至有的还有濒临灭绝的危险。文章从野外调查、生物学研究、繁殖栽培和园林应用等角度对我国苦苣苔科植物的研究进展进行综述。     

高产夏玉米镁的吸收与再分配研究

本文就高产条件下两种株型夏玉米在不同生育时期对镁的吸收、积累及镁在不同器官间的分配与再分配进行了分析。结果表明，玉米植株相对含镁量在一生中基本呈现前期高、后期低的变化趋势。植株吸收的镁在吐丝前主要分配到叶片、茎秆和叶鞘中，吐丝后镁的分配重点则转向籽粒。玉米对镁的吸收有２个高峰期，平展型品种分别在拔节至大喇叭口期和籽粒形成期；紧凑型品种分别在大喇叭口至吐丝期和灌浆始期。每形成百公斤籽粒吸收镁０．３８２～０．３９７ｋｇ。籽粒中的镁有３７．０６％～４４．０５％来自于其它器官镁的再分配。平展型品种向籽粒转移镁最多的器官是叶鞘和叶片，紧凑型品种向籽粒转移镁最多的器官是叶鞘、雄穗和叶片。     

甜菜筒喙象分布型与防治指标

本文首次报道了甜菜筒喙象卵和幼虫的田间分布型与防治指标。通过田间顺行逐株查卵,经概率分布分析看出,在百株有卵(虫)6～21粒(头)时为聚集分布。人工接卵模拟筒喙象为害采种甜菜产量损失结果表明,产量损失率与虫口密度呈幂函数相关(r=0.9913)。根据预测模型,在亩产种子100kg、单价2.2元/kg、防治费用2.85元/亩时,初拟防治指标为亩有卵420～640粒或亩有成虫20～28头为宜。     

氮素水平对甜菜干物质积累与分配的影响

通过氮素水平对甜菜干物质积累与分配影响的研究表明:甜菜植株干物质积累量与施氮量呈显著正相关,r=0.979**。提高施氮量能增加甜菜各器官干物质积累量,但施氮量超过120kg/hm2时,再增施氮肥的处理则块根增长幅度减少。干物质分配随施氮水平的提高呈现出T/R比增加的规律,只有适宜施氮,使叶根生长协调,才会获得较高产量。