Woody tissue photosynthesis and its contribution to trunk growth and bud development in young plants

Stem photosynthesis can contribute significantly to woody plant carbon balance, particularly in times when leaves are absent or in ‘open’ crowns with sufficient light penetration. We explored the significance of woody tissue (stem) photosynthesis for the carbon income in three California native plant species via measurements of chlorophyll concentrations, radial stem growth, bud biomass and stable carbon isotope composition of sugars in different plant organs. Young plants of Prunus ilicifolia, Umbellularia californica and Arctostaphylos manzanita were measured and subjected to manipulations at two levels: trunk light exclusion (100 and 50%) and complete defoliation. We found that long‐term light exclusion resulted in a reduction in chlorophyll concentration and radial growth, demonstrating that trunk assimilates contributed to trunk carbon income. In addition, bud biomass was lower in covered plants compared to uncovered plants. Excluding 100% of the ambient light from trunks on defoliated plants led to an enrichment in ¹³C of trunk phloem sugars. We attributed this effect to a reduction in photosynthetic carbon isotope discrimination against ¹³C that in turn resulted in an enrichment in ¹³C of bud sugars. Taken together our results reveal that stem photosynthesis contributes to the total carbon income of all species including the buds in defoliated plants.     

The binding of zinc,but not cadmium,by phytic acid in roots of crop plants

Plant species adapted to soils enriched with heavy metals often accumulate these metals in their above or below ground organs. In this study, electron probe microanalysis of fractured, quench-frozen root specimens of common crop species shows that an appreciable quantity of Zn can be bound as Zn phytate (myo-inositolkis-hexaphosphate) within small vacuoles of cells in the root elongation zone of lucerne, soybean, lupins, tomato, rapeseed, cabbage, radish, maize and wheat exposed to high levels of Zn (80–300 M). Globular deposits of Zn phytate are most frequently observed in the endodermis of dicotyledonous species and in the pericycle of monocotyledonous species, but may also occur in the stele and inner cortex after prolonged exposure to toxic levels of Zn. The deposits could not be found in Zn-treated sunflower, field peas and Italian ryegrass. In three crop species, lucerne, soybean and maize, Zn-induced phytate globules were frequent, but exposure of roots to 30 M Cd did not induce the formation of Cd-containing globular deposits as observed inLemna minor (Van Steveninck et al., 1990a, 1992). Simultaneous Zn and Cd treatment induced the formation of Zn phytate globules as effectively as Zn alone, and Cd was not detected in the deposits.     

Light acclimation,retrograde signalling,cell death and immune defences in plants

This review confronts the classical view of plant immune defence and light acclimation with recently published data. Earlier findings have linked plant immune defences to nucleotide‐binding site leucine‐rich repeat (NBS‐LRR)‐dependent recognition of pathogen effectors and to the role of plasma membrane‐localized NADPH‐dependent oxidoreductase (AtRbohD), reactive oxygen species (ROS) and salicylic acid (SA). However, recent results suggest that plant immune defence also depends on the absorption of excessive light energy and photorespiration. Rapid changes in light intensity and quality often cause the absorption of energy, which is in excess of that required for photosynthesis. Such excessive light energy is considered to be a factor triggering photoinhibition and disturbance in ROS/hormonal homeostasis, which leads to cell death in foliar tissues. We highlight here the tight crosstalk between ROS‐ and SA‐dependent pathways leading to light acclimation, and defence responses leading to pathogen resistance. We also show that LESION SIMULATING DISEASE 1 (LSD1) regulates and integrates these processes. Moreover, we discuss the role of plastid–nucleus signal transduction, photorespiration, photoelectrochemical signalling and ‘light memory’ in the regulation of acclimation and immune defence responses. All of these results suggest that plants have evolved a genetic system that simultaneously regulates systemic acquired resistance (SAR), cell death and systemic acquired acclimation (SAA).     

Morphological,ultrastructural, and chemical changes induced in Cunninghamella blakesleeana by copper and cobalt

Summary Scanning and transmission electron microscopy of Cunninghamella blakesleeana grown in the presence of toxic concentrations of copper and cobalt indicated that copper, but not cobalt, induced both morphological and ultrastructural changes. In contrast to the control or cobalt-grown cultures, the hyphae of copper-grown cultures (called blue mycelia) were larger in diameter, had a rough and granular surface, and the cell wall was thicker. The cytoplasm of the blue mycelia was also abnormal and was in a compressed state. X-Ray microprobe analysis indicated a lower content of magnesium and calcium in the blue mycelia and an elevated content of sulphur in both the blue and cobalt-grown mycelia. The protein composition of the cell walls of the blue mycelia, fractionated on a Sepharose-4B column saturated with copper, was different from that of control or cobalt-grown cultures, as shown by their amino acid composition. Hydroxyproline was present only in the cell wall proteins of the blue mycelia, citrulline and cystathionine were present only in the proteins of cobalt-grown cultures, and proline was absent in the cell wall protiens of the control cultures.     

Cu,Zn-superoxide dismutase is differently regulated by cadmium and lead in roots of soybean seedlings

The cadmium (Cd²⁺) and lead (Pb²⁺)-induced changes in Cu,Zn-SOD gene expression on the level of mRNA accumulation and enzyme activity were analyzed in roots of soybean (Glycine max) seedlings. The Cd²⁺ caused the induction of copper–zinc superoxide dismutase (Cu,Zn-SOD) mRNA accumulation, at each analyzed metal concentration (5–25 mg/l), whereas in Pb²⁺-treated roots this effect was observed only at the medium metal concentrations (50–100 mg/l of Pb²⁺). The analysis of Cu,Zn-SOD activity proved an increase in enzyme activity during Cd²⁺/Pb²⁺ stresses, however in Pb²⁺-treated plants the activity of enzyme was not correlated with respective mRNAs level. Presented data suggest that different metals may act on various level of Cu,Zn-SOD expression in plants exposed to heavy metals stress.     

Manganese-induced oxidative stress,ultrastructural changes,and proteomics studies in rice plants

Protoplasma - Manganese (Mn) is an essential element for plant growth but it becomes phytotoxic at higher concentrations. The effect of Mn-excess in hydroponics medium was examined on growth,...     

Chromium and cadmium removal from wastewater using duckweed - Lemna gibba L. and ultrastructural deformation due to metal toxicity

Phytoremediation potential of Lemna gibba was evaluated for chromium (Cr) and cadmium (Cd) under laboratory conditions for variable metal load of 1?mg/l, 3?mg/l, 5mgl, 7?mg/l and 9?mg/l, respectively, for 7 and 15?days of treatment period. Effects of both metals on structural attributes of L. gibba were also analyzed by Scanning Electron Microscopic (SEM) study. The metal removal percentage by L. gibba for Cr metal was found in the range of 37.3% to 98.6% and for cadmium it was found within the range of 81.6% to 94.6%. Bio concentration factor (BCF) of L .gibba was observed within the range of 37 to 295 for Cr metal and for Cd metal it ranged from 237 to 1144, which shows that the plant is a hyper accumulator for Cd metal and moderate accumulator for Cr metal. Statistical analysis (Two-way ANOVA) was performed on experimental results to confirm the individual effect of metal concentration and treatment period as well as cumulative effect of both factors together on percentage metal removal and on BCF. Research studies indicated that with the progress of treatment period metal removal percentage increases but increasing metal load during experiment negatively co-relates the metal removal percentage and BCF.     

Leaf gas exchange,reproductive development,physiological and nutritional changes of peanut as influenced by boron

Boron application at proper concentration is necessary to enhance the leaf gas exchange, physiological growth, reproductive development and nutritional improvement of crops. Therefore, an experiment was conducted to study the effects of boron to evaluate the effect on the leaf gas exchange, reproductive development, physiological and nutritional changes of peanut. Treatments comprised six levels of boron (B), viz., B₁ (0?ppm), B₂ (0.5?ppm), B₃ (1?ppm), B₄ (2?ppm), B₅ (4?ppm) and B₆ (8?ppm). Results revealed that the vegetative growth, physiological growth parameters, leaf gas exchange, reproductive characters, peg strength, shelling (%) and nutritional elements were increased for boron application. Some vegetative, physiological and reproductive traits are positively correlated with each other. Thus, this finding showed that boron can be used to culture peanut as it provides high yield and nutritional properties.     

Photosynthetic acclimation of plants to growth irradiance: the relative importance of specific leaf area and nitrogen partitioning in maximizing carbon gain

Changes in specific leaf area (SLA, projected leaf area per unit leaf dry mass) and nitrogen partitioning between proteins within leaves occur during the acclimation of plants to their growth irradiance. In this paper, the relative importance of both of these changes in maximizing carbon gain is quantified. Photosynthesis, SLA and nitrogen partitioning within leaves was determined from 10 dicotyledonous C₃ species grown in photon irradiances of 200 and 1000 µmol m^?2 s^?1. Photosynthetic rate per unit leaf area measured under the growth irradiance was, on average, three times higher for high‐light‐grown plants than for those grown under low light, and two times higher when measured near light saturation. However, light‐saturated photosynthetic rate per unit leaf dry mass was unaltered by growth irradiance because low‐light plants had double the SLA. Nitrogen concentrations per unit leaf mass were constant between the two light treatments, but plants grown in low light partitioned a larger fraction of leaf nitrogen into light harvesting. Leaf absorptance was curvilinearly related to chlorophyll content and independent of SLA. Daily photosynthesis per unit leaf dry mass under low‐light conditions was much more responsive to changes in SLA than to nitrogen partitioning. Under high light, sensitivity to nitrogen partitioning increased, but changes in SLA were still more important.     

Endophytic yeast protect plants against metal toxicity by inhibiting plant metal uptake through an ethylene-dependent mechanism

Toxic metal pollution requires significant adjustments in plant metabolism. Here, we show that the plant microbiota plays an important role in this process. The endophytic Sporobolomyces ruberrimus isolated from a serpentine population of Arabidopsis arenosa protected plants against excess metals. Coculture with its native host and Arabidopsis thaliana inhibited Fe and Ni uptake. It had no effect on host Zn and Cd uptake. Fe uptake inhibition was confirmed in wheat and rape. Our investigations show that, for the metal inhibitory effect, the interference of microorganisms in plant ethylene homeostasis is necessary. Application of an ethylene synthesis inhibitor, as well as loss-of-function mutations in canonical ethylene signalling genes, prevented metal uptake inhibition by the fungus. Coculture with S. ruberrimus significantly changed the expression of Fe homeostasis genes: IRT1, OPT3, OPT6, bHLH38 and bHLH39 in wild-type (WT) A. thaliana. The expression pattern of these genes in WT plants and in the ethylene signalling defective mutants significantly differed and coincided with the plant accumulation phenotype. Most notably, down-regulation of the expression of IRT1 solely in WT was necessary for the inhibition of metal uptake in plants. This study shows that microorganisms optimize plant Fe and Ni uptake by fine-tuning plant metal homeostasis.     

单一与复合污染条件下两种敏感性植物对Cd、Zn、Pb的吸收效应

为了进一步研究镉、锌、铅 3种重金属元素间的相互作用以及对植物吸收重金属能力的影响 ,在模拟单一重金属污染试验研究的基础上 ,采用正交回归设计方案 ,研究了 Cd、Zn、Pb复合污染情况下紫花苜蓿和披碱草两种敏感性植物对 3种重金属的吸收效应。结果表明 ,在单一污染条件下 ,镉元素对紫花苜蓿生长的影响大于锌、铅 ,铅元素对披碱草生长的影响大于锌、镉 ;紫花苜蓿对于镉的吸收累积显著高于披碱草 ,植物内镉元素浓度最高达到 1 0 88.5 mg/kg,而披碱草对于铅元素的吸收则高于紫花苜蓿 ,植物内铅元素浓度最高达到 1 3 4 5 .5 mg/kg。在复合污染条件下 ,两种植物对铅、锌和铅、镉的吸收在不同浓度范围内分别存在存在着协同效应和拮抗效应 ;同时两种植物对锌、镉元素在实验涉及浓度范围内都存在着拮抗效应。这对于深入研究复合污染条件下重金属的土壤环境化学行为 ,对植物的综合毒性以及不同植物对重金属的吸收累积效应等 ,具有一定的参考意义     

花卉植物对Cd、As、Pb污染农田的修复及其精油应用

为提高植物修复的经济价值,该文选取孔雀草、波斯菊和矢车菊三种附加值较高的花卉植物,考察其对广西某矿区Cd、As、Pb复合污染农田的修复潜力,测定分析三种花卉植物对重金属的富集和转运能力,并从修复后植物的地上部提取精油,研究植物精油对病原菌埃希氏大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphyloccocus aureus)、伤寒沙门氏菌(Salmonella typhimurium)的生长抑制效果,进一步探索植物精油作为洗手液添加剂的应用能力。结果表明:(1)试验区域内土壤污染严重,Cd、As全量超过风险管制值,Pb全量超过风险筛选值,属于Cd、As、Pb重度污染。(2)选取的三种花卉植物均可在试验区域较好地生长,其中孔雀草和波斯菊对Cd、Pb的富集与转运能力较强,对As的富集能力最弱但转运能力较强。与孔雀草和波斯菊相比,矢车菊除对Cd的转运能力较强外,对其他重金属的富集和转运能力均较弱。三种植物重金属富集能力大小排序为孔雀草>波斯菊>矢车菊,不同花卉对重金属富集偏好顺序依次为Cd>Pb>As。(3)从修复后的植物地上部提取精油进行研究分析发现,孔雀草精油对三种病原菌都具有良好的生长抑制效果(<10 CFU·mL^-1),且孔雀草体内富集的重金属并未影响精油中的重金属含量。另外,添加了孔雀草精油的洗手液,对金黄色葡萄球菌的生长抑制效果可延长至480 min。因此,孔雀草不仅可作为重金属复合污染农田的修复植物,而且修复后还可从植物体内提取精油作为抑菌剂。该研究结果为修复后重金属富集生物质的新型资源化利用提供了理论基础。     

Persistent ultrastructural changes in pancreatic acinar cells induced by 4-acetylaminofluorene

Male Leeds rats were fed a diet containing 0.05% of the non-carcinogen 4-acetylaminofluorene (4-AAF) for 8–10 months. They were then returned to a normal diet and their pancreatic tissues examined by electron microscopy at intervals between 2 and 12 months after the end of 4-AAF treatment. 4-AAF was found to induce a persistent alteration in the morphology of the granular endoplasmic reticulum, involving distortion and dilatation of the cisternae. In some respects this lesion resembles that which is induced by the carcinogenic isomer, 2-acetylaminofluorene (2-AAF).     

Reproduction of,and ultrastructural changes induced by,Spiroplasma citri in sieve tube of citrus leaves

Summary Electron microscope examination of ultrathin sections of leaf veins of stubborn—affected citrus seedlings revealed three morphotypes ofSpiroplasma citri free in the cytoplasm of mature sieve elements. In addition to these, inclusions believed to beSpiroplasma citri, some in various stages of degeneration, were occasionally found inside spherical, ovoid, or angular membraneous structures (= packets) which occurred in sieve elements devoid of any recognizable organelles. These packets which varied in size from 1.0 to 1.8 m wide an 1.9 to 3.5 m long were bounded by unit membrane ca. 9 to 10 nm thick. Spiroplasmas and packets were apparently absent in sieve elements of leaf veins of healthy citrus seedlings. Three types of packets were recognized based on the size of spiroplasmas contained: type I packets contained large, intermediate, and small spiroplasmas, but small forms predominated; type II packets contained a mixture of large and intermediate forms, while type III packets contained essentially tightly—packed large forms. Results of the study suggested that the spiroplasma-containing packets are either definite reproductive structures peculiar toSpiroplasma citri or are sieve-tube cells in various stages of plasmolysis. Evidence is presented indicating that within a given packet small spiroplasmas were produced from large spiroplasmas by some process of cell constriction followed by fission, or by budding. Since these spiroplasma—containing packets were infrequently observed in infected tissues we suggest that cell division by budding, of by constriction followed by fission into unequal daughter cells may be the principal mode of reproduction inSpiroplasma citri.     

Ultrastructural and metabolic disorders induced by short‐term cadmium exposure in Avicennia schaueriana plants and its excretion through leaf salt glands

• Environmental cadmium (Cd) sources have increased in mangrove sediments in recent decades, inducing cellular damage to many plants. Avicennia schaueriana is abundant in mangrove sites and has been subject to Cd contamination. The possible effects of Cd toxicity and the structural and physiological disturbances to this plant were studied. Can this plant express early cellular tolerance mechanisms to such metal contamination?
• Seedlings of A. schaueriana were collected from sites of their natural occurrence, placed in plastic pots containing nutrient solution for 60 days, and subsequently exposed to increasing Cd concentrations for 5 days under experimental conditions. The anatomical, ultrastructural and physiological changes induced by Cd were analysed.
• Cd accumulated mainly in the root system and in pneumatophores, stems and leaves, induced differential accumulation of mineral nutrients, but did not induce necrosis or changes in leaf anatomy. However, there was a decrease in starch grains and an increase in deposited electron‐dense material in the cortex and vascular bundles. Cd induced both increases in calcium (Ca) content in shoots and Ca oxalate crystal precipitation in leaf mesophyll and was detected in crystals and in the secretion of salt glands.
• Our observations and experimental results provide evidence of Cd tolerance in A. schaueriana. As a new feature, despite the clear cellular physiological disorders, this plant is able to eliminate Cd through leaf salt glands and immobilise it in Ca crystals, representing fast mechanisms for Cd exclusion and complexation in leaves in heavy metal coastal polluted marine ecosystems.

     

铜、铅、镉、锌、汞和银离子复合污染对水螅的急性毒性效应

以水螅(Hydrasp)为例,通过单因子静态急性毒性试验方法和等毒性溶液法,分别研究Hg2 、Cu2 、Cd2 、Ag 、Zn2 和Pb2 对其单一和复合毒性效应。单一实验结果表明,它们对水螅毒性大小顺序为Hg2 >Cu2 >Cd2 >Ag >Zn2 >Pb2 。复合毒性实验表明,Zn2 与Cu2 、Hg2 、Pb2 、Ag ;Pb2 与Cu2 ;Hg2 与Ag ;Pb2 与Ag 这些组合对水螅联合急性毒性总体上表现出拮抗作用,Cd2 与Cu2 、Hg2 、Pb2 、Ag 组合总体上则是协同作用,Zn2 与Cd2 、Pb2与Hg2 、Cu2 与Hg2 ,Ag 在不同的浓度水平组合下明显表现出不同的毒性效应。     

铅锌矿区土壤和植物重金属污染调查分析

对有色金属矿区土壤和植物重金属污染状况调查结果表明,由于遭受尾矿砂及矿毒水污染,矿区土壤极端贫瘠,土壤中Pb、Cd、Zn和Cu含量分别达764.74、4.10、372.75和95.57 mg.kg-1,重金属污染较为严重。在矿区周边有9种优势植物能够在污染土壤上定居,对Cu、Cd、Pb和Zn 4种重金属元素均有不同程度的积累,积累量均未达到超累积植物所规定的临界含量。其中的野菊花〔Dendranthema indicum(L.)Des Mou l.〕、旋鳞莎草〔Cyperusm ichelianus(L.)L ink〕、五节芒〔M iscanthus floridulus(Lab ill.)W arb.ex Schum.et Laut.〕3种植物地上部生物量较大且对某些重金属向地上部转运能力较强,对重金属污染土壤有一定的修复潜力。     

五种南极地衣的Co、Cr、Pb和Cu元素富集能力的差异

随着人类活动对全球环境的影响,环境重金属污染负荷日益增加,重金属元素向南极地区的迁移和富集已成为该地区面临的严重问题之一。地衣是研究重金属元素大气沉降特征的良好材料,但对南极地衣的重金属元素大气沉降富集能力的比较研究甚少。作者以网袋法实验比较采自西南极乔治王岛菲尔德斯半岛的5种南极优势地衣,即:王橙衣Caloplaca regalis、夹心果衣Himantormia lugubris、孔树花Ramalina terebrata、球粉衣Sphaerophorus globosus和簇花石萝Usnea aurantiacoatra对钴(Co)、铬(Cr)、铅(Pb)和铜(Cu)的富集能力。2个月的网袋法实验结果表明:1)5种地衣对Pb元素均表现出富集能力,其中夹心果衣富集能力最强,簇花石萝和孔树花次之;2)簇花石萝和夹心果衣对Cu元素的富集能力相近,球粉衣对Cu元素的富集能力较低,其他2种未表现出对Cu的富集作用;3)Co和Cr元素的富集仅分别在夹心果衣和簇花石萝中检测出来。因此,在综合检测Co、Cr、Cu和Pb的大气沉降时,可考虑簇花石萝和夹心果衣的组合;在单独检测Co、Pb和Cu的大气沉降时,夹心果衣均为最佳的物种。     

Accumulation characteristics of heavy metal Pb, Cu, Zn in Wanggang tidal flat based on Renyi theory

The vertical accumulation of heavy metals and the pollution status in Wanggang China tidal flat were studied. The base value of 210Pb in Wanggang area was obtained as 1.16 dpm/g. The fractal theories were led into the quantitative study of pollution issues. The modern average deposition rate in Wanggang area is 4.13 cm/a, according to the ²¹⁰Pb analysis. Through the correlation analysis between heavy metals, it is educed that the Fe, Cu, Pb, Zn and Li have better correlation coefficients in the area. After normalization, the nomalization values of Cu and Zn remain stable in the past 15 years. Cu shifts its value from 0.4 to 2, and Zn from 1.5 to 2.6. The information dimension of the normalized heavy metals is high in the area with loose systematic structure and lower organizational degree. The fractal dimension value of Zn moves from 3 to 6.5 with an average of 4.68; contemporary Cu from 5 to 6.5 with an average of 5.8085. The study shows that the heavy metal distribution in the area is mainly controlled by local geochemistry character with limited contribution from human activities. Meanwhile, the fractal dimension value of Pb normalization is lower, and its fractal dimension varies from 2 to 5.5 with an average of 3.608. Higher levels of self-organization of Pb mean a certain degree of lead contamination.     

Accumulation characteristics of heavy metal Pb, Cu, Zn in Wanggang tidal flat based on Renyi theory

The vertical accumulation of heavy metals and the pollution status in Wanggang China tidal flat were studied. The base value of 210Pb in Wanggang area was obtained as 1.16 dpm/g. The fractal theories were led into the quantitative study of pollution issues. The modern average deposition rate in Wanggang area is 4.13 cm/a, according to the ²¹⁰Pb analysis. Through the correlation analysis between heavy metals, it is educed that the Fe, Cu, Pb, Zn and Li have better correlation coefficients in the area. After normalization, the nomalization values of Cu and Zn remain stable in the past 15 years. Cu shifts its value from 0.4 to 2, and Zn from 1.5 to 2.6. The information dimension of the normalized heavy metals is high in the area with loose systematic structure and lower organizational degree. The fractal dimension value of Zn moves from 3 to 6.5 with an average of 4.68; contemporary Cu from 5 to 6.5 with an average of 5.8085. The study shows that the heavy metal distribution in the area is mainly controlled by local geochemistry character with limited contribution from human activities. Meanwhile, the fractal dimension value of Pb normalization is lower, and its fractal dimension varies from 2 to 5.5 with an average of 3.608. Higher levels of self-organization of Pb mean a certain degree of lead contamination.