Distribution of metals in aquatic edible plants: Trapa natans (Roxb.) Makino and Ipomoea aquatica Forsk

Most of the water bodies being used for the cultivation ofedible aquatic plants (Trapa natans and Ipomoeaaquatica) in Lucknow district, U.P., India, were found to becontaminated with a variety of toxic metals (Fe, Cu, Cr, Mn andPb). The concentration of metals Cr, Pb and Fe in water was muchhigher than recommended permissible limits of WHO (1995). Theedible parts of these plants bioconcentrated metals from theirsurrounding water significantly. Therefore, the present studywas planned to assess the metal concentration in edible part ofplants which was collected from various water bodies used forcultivation of these crops. Despite varying levels of metalsfound in various fruit parts of T. natans, the metalaccumulation in kernel was alarming. However, metal contentdecreased significantly in various parts after boiling thefruit. Similarly, I. aquatica also accumulatedsignificantly higher amounts of these metals in leaves, howeverthe metal accumulating potential varied considerably dependingupon level of metal contamination in the water body in which they were growing. The importance of these findings in theexploitation of these aquatic crops to meet the demand of foodand health perspectives for human beings is highlighted.     

Assessment of the allelopathic effect of leaf and seed extracts of Canavalia ensiformis as postemergent bioherbicides: A green alternative for sustainable agriculture

The herbicidal potential of aqueous extracts prepared from leaves and seeds of Canavalia ensiformis was tested by applying them postemergence to the crop weeds Ipomoea grandifolia and Commelina benghalensis. Considering the possible objective of using this bioherbicide on soybean fields, the extracts were also tested for deleterious effects on both transgenic and conventional soybean (Glycine max). In addition, the concentrations of four phenolic compounds and alkaloids with allelopathic properties in these extracts were estimated by high-performance liquid chromatography. The seed extract at concentrations of 25 g L^?1 and 50 g L^?1 was the most efficient postemergent bioherbicide. By applying these extracts, the development of the weed seed was progressively hindered until no recovery was observed. The application of 3.5 mL of crude extract on a plant that takes 30 days after germination of the seed to develop is sufficient for full control of the species within 5 days. Since both Ipomoea grandifolia and Commelina benghalensis are broadleaf dicotyledons, it is possible that other species with these characteristics can also be controlled or suffer the same effects under the action of the seed extract, if the same volume and mode of application are used. The selectivity of the treatments with 25 g L^?1 and 50 g L^?1 was assessed on transgenic and conventional cultivars. The treatments did not visibly affect the soybean cultivars, which developed normally during the observation period that continued up to 15 days after the death of the weeds.     

蕹菜镉积累典型品种的根际土壤酶研究

通过在镉含量高、低不同的2种土壤上的自制根箱试验并对所种植作物的镉含量进行相关性分析,研究了两种蕹菜镉积累典型品种,强坤柳叶白骨（QK,Cd-PSC）和台湾308纯白柳叶（T-308,非Cd-PSC）的根际土壤酶区系.结果表明：品种间茎叶镉含量差异极显著;在高镉条件下,蕹菜茎叶Cd含量与根际转化酶活性呈显著正相关;在低镉条件下,与根际碱性磷酸酶活性呈显著负相关.     

模拟酸雨对五爪金龙幼苗光合生理特性的影响

在华南地区,酸雨引起的农作物和经济作物生长发育障碍常导致严重的经济损失,而一些有害入侵种在酸雨条件下仍在扩散,危害性未受到明显的抑制.因此,酸雨条件下入侵种生物学特性研究有助于揭示其入侵规律.在人工环境条件下（光照培养箱的温度为30 ℃,相对湿度为47.6%,光合有效辐射为63.6 μmol·m^-2·s^-1）进行五爪金龙（Ipomoea cairica L）盆栽试验.五爪金龙幼苗每天喷施营养液.采用模拟酸雨（pH梯度为2、3、4、5、6）对幼苗进行胁迫实验,利用LI-6400便携式光合仪和分光光度法测定其光合生理特性指标.结果表明：五爪金龙叶片净光合速率随酸雨pH值的下降而降低.当光合有效辐射（PAR）低于200 μmol·m^-2·s^-1时,不同酸雨处理叶片的净光合速率均随光合有效辐射强度的增加而增大;当光合有效辐射高于200 μmol·m^-2·s^-1时,同一光合有效辐射不同pH处理叶片的净光合速率均为：CK（对照） 〉 pH6.0 〉 pH5.0 〉 pH4.0 〉 pH3.0 〉pH2.0.随着酸雨pH值的下降,光饱和点、光补偿点、最大净光合速率、表观量子效率和暗呼吸速率均呈下降的趋势.其中,pH3.0和pH2.0酸雨处理对各项光合特性参数的抑制作用均达到了显著水平.酸雨胁迫导致五爪金龙叶片叶绿素含量下降,丙二醛含量（MDA）和可溶性糖含量均显著增加,表明酸雨胁迫对叶片细胞膜系统产生了破坏作用.pH6.0、pH5.0和pH4.0酸雨处理对五爪金龙的光合生理特性影响较小,pH值为3.0和2.0的酸雨处理对五爪金龙的光合能力抑制显著.酸雨胁迫导致五爪金龙利用强光能力下降,提高了其利用弱光的能力.五爪金龙光合生理特性对酸雨环境较为敏感,对酸雨胁迫具有一定的耐受性和适应性.     

土壤水分对外来入侵植物五爪金龙植株表型可塑性和化感作用的影响

外来入侵植物五爪金龙（Ipomoea cairica）对华南地区的生态环境造成严重危害,表型可塑性可增强外来物种的入侵能力。本文通过盆栽试验研究土壤含水量为10%、20%和30%对外来入侵植物五爪金龙种子萌发、植株表型可塑性和化感作用的影响,探讨五爪金龙对土壤水分变化的响应机理,为进一步了解五爪金龙的入侵机理和提高对入侵种的预警和控制能力提供理论依据。结果表明,（1）在土壤含水量为10%,20%和30%条件下,五爪金龙种子的萌发率分别为15.2%、36.4%和33.6%。五爪金龙种子的萌发率随土壤含水量的增加而增加,尤其是在土壤含水量为30%时,五爪金龙种子萌发率最高。（2）土壤含水量为10%、20%和30%时,五爪金龙植株的总生物量分别为0.88、2.26和2.42 g。与土壤含水量为10%相比,土壤含水量为20%和30%条件下五爪金龙的总生物量分别增加了156.8%和175.0%,表明土壤水分增加显著增加了五爪金龙的总生物量。土壤含水量增加显著增加了五爪金龙的叶面积、叶生物量比、比叶面积和茎长,同时减少了根生物量比和根冠比,而对茎生物量比无显著影响。（3）相同浓度的五爪金龙水浸提液对受体植物莴苣（Lactuca sativa）和萝卜（Raphanus sativus）根长和苗高生长的化感抑制作用随着土壤含水量的减少而增强。研究表明：五爪金龙通过改变生物量分配模式和化感潜力对土壤水分变化有一定的适应能力。     

溴化1-丁基-3-甲基咪唑离子液体在空心菜中的吸收积累特性及其毒理效应

通过营养液水培的方式,研究了在不同浓度溴化1-丁基-3-甲基咪唑([C4mim]Br)对空心菜的毒性效应,测定了[C4mim]Br对空心菜各生长指标、叶绿素含量、丙二醛(MAD)含量以及根系活力的变化情况,同时研究了空心菜对[C4mim]Br的吸收和体内积累特征。结果表明:随着[C4mim]Br处理浓度与培养时间的增加,[C4mim]Br对空心菜各生理生化指标有显著抑制作用,且抑制效应具有剂量依赖型特点,半最大效应浓度(EC_(50))值为1.64 mg·L~(-1)。空心菜体内丙二醛含量显著增加表明[C4mim]Br加剧了细胞膜受损,导致根系对[C4mim]Br的吸收积累能力下降。空心菜的富集系数与转运系数均小于1,表明空心菜可以从环境中吸收并积累[C4mim]Br,但从根到地上部分转运[C4mim]Br能力较弱。     

N and P dynamics in the litter layer and soil of Mexican semi-arid forests, state of Morelos

In central Mexico, it is common for farmers to retain useful trees in abandoned lands after maize cultivation, creating a park-like landscape of scattered trees for extensive livestock grazing, among other land uses (mature forests, secondary forests, and livestock grazing in secondary forests). Among these trees Acacia cochliancantha and Ipomoea arborescens are the most common species associated with this land use in the region. The objective of this study was to assess the effects of both tree species on soil N and P recycling. To this end, we measured N and P concentrations in leaves of both species; and the seasonal N and P (total and dissolved) content in the litter, and total N and P, inorganic N, and bicarbonate-extractable-P concentrations, and the N transformations in the soil, in samples collected under crown of Acacia and Ipomoea and in open areas. Trees of different species varied in their capacity to cycle N. The leaves of Acacia were richer in N than those of Ipomoea (29.7 and 25.0 mg N g⁻¹, respectively), and nutrient resorption was higher in leguminous trees than in Ipomoea (by 20% in the case of N, and 35% in the case of P). Acacia trees had higher effects on soils than Ipomoea trees, like consistent increases of N concentrations (by 30% in the case of total N, and by 50% in the case of inorganic N) and transformations (N mineralization and nitrification in rainy season increases by a factor of 20 and 36, respectively). On the other hand, Ipomoea produced senescent leaves and accumulated forest litter with less P concentration (0.8 and 0.7 mg P g⁻¹, respectively) in relation to Acacia (senescent leaves: 1.3 mg P g⁻¹; litter: 1.1 mg P g⁻¹), reflecting the lower availability of the nutrient in the soil. The total litter N and P pools decreased in the rainy season under crown of both species, as the dissolved P pool did. The total soil N and P concentrations did not change with sampling season. However, potential N transformations and bicarbonate P under both species were higher in dry season than in rainy season samples. Comparison with other land uses in the region suggests that the Acacia–Ipomoea system cycles low quantity of nutrients, but there are no notable differences in the availability of P in the soils. These results demonstrate that scattered trees improve the N and P cycling following the discontinuation of agricultural practices, and the effects will vary depending on the tree species.     

Faecal shield chemical defence is not important in larvae of the tortoise beetle Chelymorpha reimoseri (Chrysomelidae: Cassidinae: Stolaini)

The most frequently investigated defence mechanism among larvae of tortoise beetles is protection by faecal shields, which generally present chemicals that are directly sequestered and/or modified from larval host-plants. In the present work we investigate the tortoise beetle Chelymorpha reimoseri that feeds on the leaves of Ipomoea carnea fistulosa (Convolvulaceae), seeking for the importance of this mechanism to their larvae. We show that 4th instar larvae suffer low predation regardless of the presence of shields in field and laboratory bioassays with ants and chicks. Chloroform extract from larvae without shields provided high protection against predation as shown in bioassays in the field, as well as against chicks, suggesting that C. reimoseri does not rely on the shield for protection. The aqueous extract of the shields did not show activity in such bioassays. The compounds responsible for this protection have yet to be identified, and it remains an open question as to whether they are sequestered from the host plant or de novo biosynthesized. This is the first record of chemical defence in cassidine beetles without the need for faecal shields. These findings indicate that more attention should be paid to chemicals present in the tissues of larvae and/or adults of tortoise beetles; the protective compounds sequestered from host plants or de novo biosynthesized can provide an alternative or complementary strategy against predation in these insects.     

浮床水培蕹菜的生物学特征及水质净化效果

本研究比较了污染水体中浮床水培蕹菜与陆生同种蕹菜之间生长特性以及N、P含量的差异。结果表明,水培蕹菜单株鲜重约为792．5g／株,为陆生蕹菜的3．53倍;单株N、P总量分别比陆生高469．6％、566．7％。水培蕹菜与其他水培植物相比具有较强的N、P吸收力,是一种可用于富营养化水体水质净化的优良植物。     

城市污泥对通菜-水稻土中有机污染物的累积效应

在水稻土上施用城市污泥及化肥盆栽通菜,应用GC/MS对通菜植株和土壤中的邻苯二甲酸酯(PAEs)和多环芳烃(PAHs)等7类43有机污染物进行系统分析,探讨通菜植株和土壤中其累积效应.结果表明,通菜植株中检出邻苯二甲酸酯、多环芳烃、氯苯类、硝基苯类、醚类和卤代烃类共6类28种化合物(胺类未检出),土壤中检出上述7类33种化合物,均以PAEs和PAHs为主,其总含量是其他类污染物的几倍或数十倍.不同处理的通菜和土壤中各类有机污染物的含量差别较大,均以个别或少数污染物为主.施用城市污泥增加了植株和土壤中PAEs和PAHs等污染物的含量.强致癌性化合物苯并(a)芘在通菜中被检出,在部分土壤中的含量超过加拿大土壤质量控制标准(1.0mg/kg).除佛山污泥处理的通菜对氯苯类和醚类的生物浓缩系数(BCF)大于1外,其余均小于1.0.