Effect of Arsenic on Growth,Arsenic Uptake,Distribution of Nutrient Elements and Thiols in Seedlings of Wrightia arborea (Dennst.) Mabb.

Hydroponic experiments were conducted to investigate the effect of arsenic on seedlings of Wrightia arborea and Holoptelea integrifolia. Results revealed that W. arborea could tolerate much higher arsenic concentration than H. integrifolia. Therefore, further investigations were focused on W. arborea using higher arsenic concentrations (0.2–2.0 mM). Seedlings of W. arborea accumulated about 312–2147 and 1048–5688 mg/kg dry weight of arsenic in shoots and roots, respectively, following treatments with 0.2–1.5 mM of arsenic without exhibiting arsenic toxicity signs. However, arsenic at 2.0 mM caused decline in growth. Macronutrients content such as Ca, S (except at 2.0 mM), and K (only in root) increased while Mg, P, and K (shoot) decreased by arsenic treatments. However, the content of micronutrients was enhanced under arsenic treatments. Non-protein thiols (NP-SH) showed positive correlations with arsenic doses up to 0.2–1.5 mM but at 2.0 mM there was a decline in NP-SH thus suggesting important role of NP-SH in imparting arsenic tolerance. This study demonstrated that W. arborea that could tolerate arsenic concentrations up to 0.2–1.5 mM may be useful in arsenic phytoremediation programs.     

间作对植株生长及养分吸收和根际环境的影响

通过盆栽实验研究了线辣椒和玉米间作对其植株生长、矿质养分吸收、根际环境以及铁载体分泌的影响,以探索间作促进铁、磷等养分吸收利用的可能生理机制.结果表明:(1)与单作相比,间作线辣椒地上部干重降低23.0%,根系干重增加44.2%,玉米地上部和根系的干重分别增加8.7%和22.9%;间作线辣椒根冠比和根系活力分别显著提高86.4%和29.8%;间作线辣椒、玉米叶绿素含量分别显著提高12.6%和7.8%.(2)与单作相比,间作线辣椒的铁、锌、锰含量分别增加1.50倍、1.39倍和1.34%,而间作玉米则无显著变化;间作线辣椒和玉米的钙含量都显著低于相应单作,氮含量没有显著变化,但磷、钾含量显著增加.(3)间作线辣椒和玉米的根际土、非根际土的酸性磷酸酶活性及根系酸性磷酸酶活性都显著高于相应单作,而其根际土和非根际土的pH值无显著变化;间作玉米根系的铁载体分泌比单作减少32.8%,间作线辣椒根系的铁还原酶活性是单作的1.10倍.研究发现,线辣椒/玉米间作能通过影响根际生物学特征和化学过程提高植株的铁、锌、磷和钾养分水平,缓解养分胁迫,是一种很有推广价值的种植模式.     

New Physiological Effects of 5-Aminolevulinic Acid in Plants: The Increase of Photosynthesis,Chlorophyll Content,and Plant Growth

5-Aminolevulinic acid (ALA) promoted the growth and yield of several crops and vegetables at concentrations lower than those eliciting herbicidal responses, i.e., less than 1.8 mm by foliar spray and 60 μm by root soaking. To evaluate the physiological action of ALA, the effects of ALA on plants were examined by several bioassay systems at 0.0006–600 μm. ALA at 0.06–6 μm by root soaking increased the growth of rice seedlings in light, but did not affect this in darkness. In horseradish shoot primordia, promotion by ALA was not proportional among total chlorophyll content, chlorophyll concentration, and fresh weight. In the test using pothos, ALA at 0.06 μm elicited the accumulation of chlorophyll, but the photosynthesis of the plants was promoted by treatment together with ALA and nutrients. These results suggest that ALA have a variety of plant physiological effects on chlorophyll synthesis, photosynthesis, and plant growth, and ALA acts as a growth regulator in plants at low concentrations. These effects of ALA were also assumed to be linked to light irradiation and an uptake of fertilizer by plants. However, excess ALA suppressed these effects.     

The Effect of Humidity on Water Uptake by, and Viscous Flow Resistance of, Excised Leaves of a Number of Species: Physiological and Anatomical Observations

Water uptake, used as an indication of transpiration, and viscousflow resistance, used as an indication of stomatal aperture,were measured for leaves or shoots of 26 species in a leaf chamber.The relative humidity of the air in the chamber was varied betweenapproximately 15 and 90%. Stomata of 10 species showed a directresponse to humidity. The humidity response was not related to the number of ectodesmataor to the arrangement of vascular tissues. Those species whichshowed a direct stomatal response to humidity were found tohave, on average, larger substomatal cavities (measured in transversesection) than the other species. The presence or absence ofthe humidity response is not linked to the normal habitat ofa species, but seems to be related to its phylogeny.     

遮荫对掌叶半夏生长、产量及光合生理特性的影响研究

目的：研究遮荫对掌叶半夏生长、药材产量和光合生理指标的影响,分析适宜掌叶半夏药材高产的遮荫度,探寻其产量差异形成的光合生理机制。方法：采用遮荫网遮荫,共设置了5种光强处理,透光率分别为全光对照CK（100%）、T1（75%）、T2（65%）、T3（50%）、T4（25%）,测定各遮荫处理下掌叶半夏的株高、单株叶片数、单株叶面积、单片叶面积、药材产量、叶绿素含量、光合日进程和叶绿素荧光参数。结果：（1）遮荫可显著（P〈0.01）提高掌叶半夏的株高、单株叶面积和叶绿素含量;（2）光合日进程曲线测定结果表明,除T4处理外其他处理均发生光合＂午休＂现象,日平均光合速率（Pn）以T1处理最高,绝对光能利用率（Eu）以T3处理最高;（3）叶绿素荧光参数测定结果表明,CK的Fv/Fm最低,发生的原因可能与PSⅡ反应中心的光化学伤害有关;（4）药材产量以T2处理最高,较CK增产56.34%。结论：掌叶半夏更适宜在遮荫条件下栽培,透光率在65%时有利于掌叶半夏药材高产,其产量差异的形成可能与日均光合速率的不均衡有关。     

Growth Responses of Two Solanum Species to Contrasting Temperatures and Irradiance Levels: Relations to Photosynthesis, Dark Respiration and Chlorophyll Fluorescence

Potato production in the tropical lowlands during the rainyseason is constrained by high temperature and low irradiance.This study examined the effect of these two variables on drymatter production and allocation, using plant growth, leaf anatomy,gas exchange and chlorophyll fluorescence measurements. Plantsof two clones, Solanum goniocalyx cv. Garhuash Huayro (GH) andDTO-33, a heat tolerant clone of S. tuberosum x S. phureja,were grown in growth chambers at 33/25 °C or 20/10 °Cday/night temperature. At each temperature, plants were grownin either 12 h high irradiance (430–450 µmol m^–2s^–1 PAR) or 12 h low irradiance (250–280 µmolm^–2 s^–1) both with a 6–h photoperiod extensionof 6 µmol m^–2 s^–1. Plants were harvested after10 d (initial harvest) and after 20 d (final harvest). By theend of the study DTO-33 had produced more dry matter and hadtuberized, whereas GH had a greater leaf area ratio (LAR) andspecific leaf area (SLA). The highest relative growth rate (RGR)was at low temperature and low irradiance, possibly due to acombination of thin leaves with a large surface area. At thehigh temperature, low irradiance had the opposite effect, producingthe lowest net assimilation rate (NAR) and lowest RGR. Bothtuber number and weight were markedly reduced by high temperature.Low irradiance, in combination with high temperature, producedvirtually no tubers. Stomatal density, which was greater onGH than in DTO-33, was increased at high temperature. When measuredat 30 °C both clones, especially DTO-33, showed heat-adaptationin terms of ability to maintain a high rate of net photosynthesisat 30 °C. Plants grown at high irr-adiance and low temperaturehad the lowest net photosynthetic rate at 30 °C. Concurrentmeasurements of chlorophyll fluorescence indicated that onlythe initial (O) fluorescence parameter was affected. The dataconfirm the field observation that reduction in potato growthat high temperature can be aggravated by lower irradiance. Thisreduction is associated with a reduced leaf area and NAR. Growth analysis, heat adaptation, light     

Effects of Organic Enrichment of Mine Spoil on Growth and Nutrient Uptake in Oak Seedlings Inoculated with Selected Ectomycorrhizal Fungi

Abstract Poor growth of Quercus robur L. (oak) trees has been reported on mine sites where overburden and subsoil have been used in the reinstatement of surface layers. This stunting has been attributed to a lack of macronutrients and to an adverse soil environment for root growth and mycorrhizal development. Growth, mineral nutrition, and ectomycorrhizal colonization of Q. robur seedlings were studied in an experiment carried out under controlled growing conditions in which mine spoil material was enriched with a leaf litter mulch. Enrichment of mine spoil material was found to produce a significant increase in growth and foliar N concentrations of oak seedlings. Inoculation with three taxa of ectomycorrhizal fungi did not benefit seedlings when mine spoil was the only substrate, possibly due to the poor physical properties of the unamended spoil and lack of nutrients. Inoculation with two taxa, Laccaria laccata and Hebeloma crustuliniforme, isolated from 3‐year‐old trees produced a significant stimulation of growth in the organically enriched treatment, which was believed to be due to greater uptake of mineralized N. However, Cortinarius anomalus isolated from fruit bodies associated with a 15‐year‐old tree did not increase biomass. The presence of organic matter was found to result in a significant stimulation of mycorrhizal infection by both inoculum and contaminant mycobionts. Recommendations are made for improving the establishment and growth of oak seedlings on reinstated sites.     

Uptake and Distribution of Stable Strontium in 26 Cultivars of Three Crop Species: Oats,Wheat, and Barley for Their Potential Use in Phytoremediation

The main objective of this study was to investigate the accumulation and distribution of strontium (Sr) in 26 cultivars of wheat (Triticum aestivum L.), husk oat (Avena sativa L) and naked oat (Avena nuda), and barley (Hordeum vulgare L.) for their potential use in phytoremediation.Sr levels had no effect on the accumulation of shoot biomass at tillering or at maturity. Mean shoot Sr concentration of naked oat and barley at tillering was significantly (P < 0.05) higher than that of wheat; Neimengkeyimai-1, a naked oat cultivar, had the highest Sr concentrations. At maturity, of four naked oat cultivars, Neimengkeyimai-1 had the highest Sr content at all measured Sr levels. Leaves had the highest Sr concentrations, followed by roots and straw, and then grain with the lowest. Mean enrichment coefficients from soil to shoots ranged from 0.521 to 1.343; the percentage of stable Sr removed from the soil to the shoots at harvest time was more than 1.4% after 120 days. Neimengkeyimai-1 could be used as a model for further research to find more effective cultivars; and naked oat plants could be selected for phytoremediation to clean up contaminated soil.     

Inoculation of Cucumber (Cucumis sativus L.) Seedlings with Salt-Tolerant Plant Growth Promoting Bacteria Improves Nutrient Uptake,Plant Attributes and Physiological Profiles

Journal of Plant Growth Regulation - Salinity is one of the major abiotic stresses that cause retarded plant growth and crop production. It has been reported that harmful effects of salinity could...     

Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance,Photosensitizer Uptake and Reactive Oxygen Species Generation

The increasing applicability of antifungal treatments, the limited range of available drug classes and the emergence of drug resistance in Candida spp. suggest the need for new treatment options. To explore the applicability of C. albicans photoinactivation, we examined nine structurally different imidazoacridinone derivatives as photosensitizing agents. The most effective derivatives showed a >10⁴-fold reduction of viable cell numbers. The fungicidal action of the three most active compounds was compared at different radiant powers(3.5 to 63 mW/cm²), and this analysis indicated that 7 mW/cm² was the most efficient. The intracellular accumulation of these compounds in fungal cells correlated with the fungicidal activity of all 9 derivatives. The lack of effect of verapamil, an inhibitor targeting Candida ABC efflux pumps, suggests that these imidazoacridinones are not substrates for ABC transporters. Thus, unlike azoles, a major class of antifungals used against Candida, ABC transporter-mediated resistance is unlikely. Electron paramagnetic resonance (EPR)-spin trapping data suggested that the fungicidal light-induced action of these derivatives might depend on the production of superoxide anion. The highest generation rate of superoxide anion was observed for 1330H, 1610H, and 1611. Singlet oxygen production was also detected upon the irradiation of imidazoacridinone derivatives with UV laser light, with a low to moderate yield, depending on the type of compound. Thus, imidazoacridinone derivatives examined in the present study might act via mixed type I/type II photodynamic mechanism. The presented data indicate lack of direct correlation between the structures of studied imidazoacridinones, cell killing ability, and ROS production. However, we showed for the first time that for imidazoacridinones not only intracellular accumulation is necessary prerequisite of lethal photosensitization of C. albicans, but also localization within particular cellular structures. Our findings present IA derivatives as efficient antifungal photosensitizers with a potential to be used in local treatment of Candida infection.     

Behavior and Physiology of the Redside Dace, Clinostomus elongatus, a Threatened Species in Michigan

The threatened status of redside dace, Clinostomus elongatus, in Michigan inhibits study and management of remnant populations of the species. We present a phenotypic approach to evaluate the use of redside dace from New York as behavioral and physiological models for Michigan populations. We evaluated behavioral similarity by comparing patterns of microhabitat use and physiological similarity by comparing resting routine metabolic rates measured in the field. Variation between sites in available microhabitat made direct comparisons difficult; however, redside dace in Michigan and New York showed a common preference for mid-water positions in the deepest parts of pools under overhanging structure. Field measurements at 10°C showed that Michigan fish had higher metabolic rates than rates predicted for New York fish at the same temperature, though biological significance of this difference is questionable. In laboratory experiments, we measured metabolic rate and upper thermal tolerance in relation to acclimation temperatures of 6–20°C using redside dace collected from four streams in New York. Redside dace showed a significant increase in metabolic rate as acclimation temperature increased (Q₁₀=2.3). Critical thermal maxima (CTM) of New York redside dace also increased with acclimation temperature. Obstacles related to the transferability of habitat use data and variation in physiology due to uncontrolled and unmeasured environmental factors in the field lead us to urge caution when extrapolating behavioral and physiological characteristics between widely-separated populations of a species. Despite these obstacles, we described useful patterns of microhabitat use and provided estimates of physiological tolerances that will assist resource managers in the recovery of Michigan redside dace.     

南亚热带酸雨地区陆地生态系统植被、土壤与地表水现状的研究

工业化程度的不断提高给环境带来的压力是全球性的普遍问题。矿物燃料的大量使用 ,使大气中ＳＯ2 、ＮＯＸ 和其它酸性颗粒物等污染物浓度增加 ,导致大气环境质量恶化 ,影响全球植被生态系统的生产力。排放到大气中的ＳＯ2 、ＮＯＸ 是形成酸雨的重要来源 ,大范围的迁移是它的一个重要特征。国内外已取得的研究结果证明 ,ＳＯ2 、ＮＯＸ等污染气体及其沉降化合物直接导致植物生长量生物量的下降、叶伤害、光合作用减弱、呼吸作用增强。另一方面 ,酸雨的形成导致土壤酸化、土壤缓冲能力下降、Ａ1离子的释放、盐基离子的淋洗、营养亏损 ,使树…     

叶绿素b含量低的水稻突变体的光合功能衰退及其与活性氧的关系

研究了一个在田间发现的水稻叶绿素b含量低的突变体叶片的光合功能衰退。和野生型相比,突变体的光合功能在叶片一生中较稳定;超氧阴离子和H2O2含量低,但活性氧清除系统的SOD和CAT酶活性差异不显著。由于突变体叶片中还原态辅酶Ⅱ和氧化态辅酶Ⅱ的比值低于野生型,因而认为其光合电子传递速率和羧化反应消耗电子速率之间比野生型更加平衡,是其光合功能较野生型稳定的原因。     

Nutrient limitations in wet, drained and rewetted fen meadows: evaluation of methods and results

Restoration of wet grassland communities on peat soils involves management of nutrient supply and hydrology. The concept of nutrient limitation was discussed as well as its interaction with drainage and rewetting of severely drained peat soils. Different methods of assessing nutrient limitation were compared and the type and extent of nutrient limitation were determined for several wet grassland communities. It was concluded that a full-factorial field fertilisation experiment is the most preferable method. Plant tissue analyses and soil chemical analyses were considered less suitable, although they may provide helpful additional information. Fertilisation experiments in the laboratory using sods or using test plants appear to be the proper means to study mechanisms or processes, but have a restricted predictive value for field situations. Generalising the results, it seems that many relativily undisturbed grassland plant communities on peaty soils are characterised by N limitation. Phosphate limitation for vegetation on peat soils is mainly observed in specific circumstances such as extreme calcium richness, high concentrations of Fe or as a result of drainage or long-term hay cropping. The latter two may also cause K limitation. Rewetting is regarded as a prerequisite in restoring wet grassland communities. Further restoration measures to influence nutrient availability depend on aims of the management and the individual site conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of Mn Deficiency on Growth,Chlorophyll Content,Physiology, and Essential Monoterpene Oil(s) in Genotypes of Spearmint (Mentha Spicata L.)

At various intervals after inoculation of the roots of groundnut plants with the fungus Macrophomina phaseoli, ¹⁴CO₂ was administered to branch 2 (from the base) of the plants in the light. The effects of the disease on the translocation of ¹⁴C-photosynthates out of the source branch to the rest of the plant were studied 24 h after labelling. As the plant aged and the disease symptom development became more evident, an increasing percentage of the fixed ¹⁴C-photosynthates was exported from branch 2 of the inoculated plants (IP) compared to the non-inoculated plants (NIP). The apex, main stem, and branch 1 of NIP imported more of the total fixed ¹⁴C throughout the developmental stages of the plant except for day 10 after inoculation when branch 1 of IP imported almost 76 % of the total fixed ¹⁴C. The roots of IP were the major sink and imported higher percent of the total fixed ¹⁴C than the roots of NIP. This revised version was published online in August 2006 with corrections to the Cover Date.     

Redescription of Lagenophrys eupagurus Kellicott (Ciliophora, Peritricha, Lagenophryidae) and a Comparison of It with Three Similar Species

Lagenophrys eupagurus , a poorly known loricate peritrich ectocommensal on the hermit crab Pagurus longicarpus , has been rediscovered and is redescribed. Lagenophrys lunatus and L. articularis were found to be conspecific with L. eupagurus based on close similarities, especially with regard to structure of the lorica aperture and proportions of the lorica. Lagenophrys callinectes , although resembling L. eupagurus , was determined to be a separate species because of distinct, consistent differences in structure of the lorica aperture and proportions of the lorica. Lagenophrys eupagurus and L. callinectes share some features of the lorica aperture with 3 other species of Lagenophrys , prompting the speculation that the 5 species may constitute a cluster of related species within the genus. Lagenophrys eupagurus utilizes a relatively wide variety of hosts compared to other species of Lagenophrys and appears to subsist mainly on phytoplankton. In some cases, the feeding behavior of the host may assist L. eupagurus in obtaining food. Lagenophrys callinectes appears to be restricted to brachyuran crabs of the genus Callinectes. It appears to be a bacterivore and is probably assisted in obtaining food by the preference of its hosts for estuarine areas that are rich in organic material.