Preparation and characterization of two supramolecular complexes with 5-amino-2,4,6-triiodoisophthalic acid under N-donor auxiliary ligand intervention

Assemblies of 5-amino-2,4,6-triiodoisophthalic acid (H₂ATIBDC) with Cd(II) and Zn(II) in the presence of N-donor auxiliary ligand, 1,4-bis(1,2,4-triazol-1-yl)butane (btb), at ambient conditions yield two new supramolecular complexes, [Cd(ATIBDC)(btb)(H₂O)₂]·3H₂O (1), and [Zn(ATIBDC)(btb)]·2H₂O (2). Generally, these two complexes display 1D ATIBDC²⁻-bridged coordination arrays. Distinct extended 3D network architectures are further constructed with the help of weak secondary interactions especially aromatic stacking, halogen bonding, and hydrogen bonding as supramolecular driving forces. It is worthy to mention that halogen bonds (C-I?π and C-I?N/O) play important roles in the supramolecular assembly. The pentameric cluster (H₂O)₅ in 1 assembles into highly ordered helical infinite chains. Complex 2 exhibits the fascinating single-walled tube-like chain structure. It loses crystallinity rapidly in the air and leads to the formation of [Zn(ATIBDC)(btb)]·H₂O (2A). Thermal stabilities and solid state fluorescent properties of complexes 1 and 2A have been studied.     

Effects of Sludge and pH Adjustment on Cd Speciation in Soil and Growth and Cd Accumulation in Pak Choi

The objective of this study was to assess the effects of soil pH adjustment and treatment with sludge on plant growth and cadmium (Cd) accumulation in Chinese cabbage (pak choi) grown in Cd-contaminated soils. Soil was artificially spiked to raise its final Cd concentration to 10 mg/kg, adjusted to different pH values, and then supplemented with 5% sludge: either biosolids (BS) from wastewater treatment or sludge from drinking water treatment (WTS). Pak choi seeds were sown and the seedlings potted in the treated soil, then grown in a greenhouse for 45 days. The added Cd was present mainly in the exchangeable fraction and its concentration correlated to Cd accumulation in the roots and shoots. Adjustment of pH and application of sludge affected the Cd concentration in different fractions. Addition of WTS and adjustment to pH 7.0 inhibited growth and Cd accumulation in the pak choi. Addition of BS increased the soil nutrient content and thus enhanced growth and Cd accumulation. If pak choi were the only form of vegetable intake, consumption of pak choi grown in the Cd-spiked soils used in this study would exceed the maximum acceptable intake (60 μg/day) proposed by the World Health Organization.     

Effect of soil Cd addition on germination of native plant species

Soil Cd addition was found to adversely affect germination ofAndropogon scoparius, Monarda fistulosa, andRudbeckia hirta. Rudbeckia germination was found to be most sensitive to soil Cd addition andAndropogon germination most tolerant (b=–.0001). Soil cadmium concentrations sufficient to reduce germination by 25% were calculated to be 30 and 46 g Cd/g soil forRudbeckia andAndropogon respectively.Contribution from Purdue University Agricultural Experiment Station, West Lafayette, Indiana 47907. AES Journal No. 7594. This work was supported by federal funds from the National Science Foundation — RANN Program.     

Heavy metal accumulation in iron plaque and growth of rice plants upon exposure to single and combined contamination by copper, cadmium and lead

A pot experiment was conducted to evaluate the bioaccumulation of heavy metals and growth response of rice plants after exposure to single and combined contamination by Cu, Cd and Pb. The results showed that the biomass production was not significantly affected by either single or combined treatment of Cu, Cd and Pb. Adding Cu (Cd, or Pb) separately all increased concentrations of the respective element in root and shoot (p < 0.001). In the combined contamination, Pb promoted both root and shoot absorption of Cu and Cd (p < 0.001), and Cu affected Cd and Pb absorption in the root, but Pb concentrations in both root and shoot were not affected by Cd application. The formation of iron plaques varied obviously with soil types. Heavy metal accumulation in iron plaques was induced by the three elements (p < 0.001). Furthermore, the three heavy metals exhibited an interactive relationship as measured by the Cu, Cd, Pb and Fe concentrations in root surface iron plaques. The iron plaques partially inhibited transfer of Pb to root and shoot, but no such effect was observed for Cu and Cd. This research indicates that the interaction among different heavy metal elements is very complex. It is very important to have a clear understanding on the associated mechanism and the consequential impact on plant growth.     

小麦幼苗生长及其抗氧化酶活性对模拟酸雨与金属离子复合胁迫的响应

通过水培试验,研究了模拟酸雨(pH 3.5)与Al(3、30 mg/L)、Pb(25、250 mg/L)、Cd(0.11、mg/L)单独或复合胁迫对小麦幼苗生长及抗氧化酶活性的影响。结果表明,模拟酸雨与Al、Pb、Cd单独或复合处理12 d后,小麦幼苗根长降低54.01%~94.81%,苗高降低18.88%~77.95%,单粒萌根数降低21.87%~80.37%,其生长发育受到显著抑制,抑制效应随处理浓度增大和作用时间延长而增强,且复合处理组抑制效应更强;幼苗根部超氧化物歧化酶(SOD)活性在模拟酸雨与单一金属离子处理下显著升高,而在3种金属离子复合处理下显著降低,但酸性条件下无论金属离子单独及复合处理后,过氧化物酶(POD)活性均显著升高,过氧化氢酶(CAT)活性均明显下降。研究发现,酸性条件下3种金属离子对植物细胞均产生氧化胁迫作用,且它们复合胁迫的毒性效应大于其单独胁迫。     

Heavy metal composition of polysomal fractions following cadmium challenge

Endogeneous levels of zinc and copper were found to be 1.2±0.1×10⁻² and 0.3±0.1×10⁻² μg/A260 unit, respectively, in polysomal fractions from control animals; cadmium, however, was undetectable. In experimental animals (injected with cadmium) zinc, copper, and cadmium were found in polysomal fractions isolated by two different methods. One hour after a cadmium injection there was a rise in both the zinc and copper content of the polysomal fractions, which then declined steadily to below control levels by 16 h. Neither zinc nor cadmium were dialyzable from these fractions by a TRIS buffer; however, addition of 0.01M EDTA to the buffer resulted in removal of 75% of the zinc and all of the detectable cadmium. The addition of cadmium (CdCl₂) to control supernatants (adjusted to the cadmium concentration present in supernatants 6 h after in vivo exposure) resulted in metal binding to polysomal fractions in levels comparable to those observed after in vivo exposures to the metal. When cadmium was added in the form of cadmium thionein, a smaller fraction of the metal was isolated with the polysomal fraction. Cadmium bound to polysomal fractions in vivo (24 h after exposure) was sensitive to release by protease digestion, but insensitive to release by ribonuclease digestion.     

Zinc in plants

Zinc (Zn) is an essential component of thousands of proteins in plants, although it is toxic in excess. In this review, the dominant fluxes of Zn in the soil-root-shoot continuum are described, including Zn inputs to soils, the plant availability of soluble Zn(2+) at the root surface, and plant uptake and accumulation of Zn. Knowledge of these fluxes can inform agronomic and genetic strategies to address the widespread problem of Zn-limited crop growth. Substantial within-species genetic variation in Zn composition is being used to alleviate human dietary Zn deficiencies through biofortification. Intriguingly, a meta-analysis of data from an extensive literature survey indicates that a small proportion of the genetic variation in shoot Zn concentration can be attributed to evolutionary processes whose effects manifest above the family level. Remarkable insights into the evolutionary potential of plants to respond to elevated soil Zn have recently been made through detailed anatomical, physiological, chemical, genetic and molecular characterizations of the brassicaceous Zn hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri.     

Alleviation of Cadmium Toxicity to <i>Medicago Truncatula</i> by AMF Involves the Changes of Cd Speciation in Rhizosphere Soil and Subcellular Distribution

Arbuscular mycorrhizal fungi (AMF) can improve plant tolerance to several abiotic stresses, including heavy metals, drought or salinity exposure. However, the role of AMF in alleviation of soil cadmium (Cd)-induced toxicity to plants is still largely unknown. In this study, Cd speciation in soil and subcellular distribution of Cd were used to characterize the roles of application AM fungi in the alleviation of Cd toxicity in alfalfa plants. Our results showed that the addition of Glomus mosseae in Cd contaminated soil (10 mg/Kg) significantly increased soil pH, cation exchange capacity (CEC) and organic matter in rhizosphere soil with Medicago truncatula L., and then account for significantly decreased contents of exchangeable and carbonate-bounded Cd speciation in rhizosphere soil, indicating alleviation of plant toxicity by reduction of bioavailable fractions of Cd. Although there is no significant difference found in Cd accumulation by roots and shoots respectively between Cd and AM-Cd treatments, more portion of Cd was recorded compartmentalization in cell wall fraction of both root and shoot in treatment of Cd with AM application, indicating alleviation of Cd toxicity to plant cell. Herein, application of AM fungi in Cd treatments performed to inhibit the appearance of Cd toxicity symptoms, including the improvement of leaf electrolyte leakage, root elongation, seedling growth and biomass. This information provides a clearer understanding of detoxification strategy of AM fungi on Cd behavior with development and stabilization of soil structure and subcellular distribution of plant.     

镉对茶条槭和五角槭光合作用和叶绿素荧光特性的影响

以北方阔叶树种茶条槭(Acer ginnala)和五角槭(Acer mono)2年生苗木为材料,采用土壤和风化砂混合物作为盆栽基质,设置0(CK)、10、50、100、200 mg·kg-1 5种土壤镉浓度,研究了土壤镉胁迫对苗木叶片光合作用和叶绿素荧光特性的影响.结果表明:随着土壤镉胁迫浓度增加,茶条槭净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)先升后降,胞间二氧化碳浓度(Ci)则先降后升,且均在10 mg·kg-1 Cd2+时达到峰值或谷值;同时五角槭的Pn逐渐降低,Ci持续升高,Gs和Tr则先升后降且均在10 mg·kg-1 Cd2+时达到峰值.随土壤镉处理浓度的增加,茶条槭和五角槭的Fv/Fm、Fv/F0和qN均呈先升后降趋势,ΦPSⅡ则均持续下降;qP在茶条槭表现为先升后降,而在五角槭则逐渐下降.所有指标(除Ci外)在随镉浓度的变化过程中,其上升幅度均为茶条槭大于五角槭,而下降幅度则为五角槭大于茶条槭.研究发现,重金属镉通过破坏或抑制光合作用过程来影响茶条槭和五角槭的生长,高浓度镉导致的Pn下降是由非气孔限制因素所致;茶条槭对土壤镉的耐性大于五角槭,100和50 mg·kg-1 Cd2+可能分别是茶条槭和五角槭对土壤镉污染的耐受极限.     

Pot experiment to study the uptake of Cd and Pb by three Indian mustards (Brassica juncea) grown in artificially contaminated soils

Most of the metals-contaminated and fallow lands in Taiwan are a result of irrigation with illegal effluent of factories. Phytoextraction methods can be applied to reach the target of fallow-lands reuse and earn more incomes for farmers. In many studies, Indian mustards (Brassica juncea) were planted in the metal-contaminated soils to study their suitability in phytoextraction. However, the total removal of metals by plants was quite different between accessions. In this pot study, three accessions of B. juncea (cv. 182921, cv. 211000, and cv. 426308) were planted in artificially Cd- or Pb-contaminated soils to investigate the differences between them. EDTA was applied to study its effect in increasing the bioavailability of Cd and Pb and their uptake by these Indian mustards. Experimental result showed that three accessions of Indian mustard can accumulate a high concentration of Cd and Pb when growing in the artificially Cd- and Pb-contaminated soils. Their shoot Cd or Pb concentrations were significantly enhanced, resulting from the application of EDTA. Among the three accessions, B. juncea cv. 211000 accumulated the highest concentrations of Cd and Pb in their shoots compared with B. juncea cv. 182921 and cv. 426308, but its total removal was the lowest due to its lower biomass.