Lead accumulation from non-saline and saline environment by Tamarix smyrnensis Bunge

Tamarix smyrnensis plants were exposed to Pb(NO₃)₂, with and without addition of salt into soil for 10 weeks. Salt as NaCl was added to water for watering in concentrations 0.5% and 3%. Subsequently, lead uptake was quantified in leaves and roots of the plants by ICP-AES spectrometry. In addition, the influence of Pb on photosynthesis and other physiological parameters was also examined by means of biomass production and shoot length determination. Plant appearance was observed also. The influence of Pb presence in the soil on chlorophyll content was examined. In order to quantify the fate of Pb in the plant, metal excretion by salt glands was investigated as well. It was found that the roots were the main accumulation site of Pb in all plants under all treatments irrespective of salt concentration in soil. Low salinity in soil did not affect Pb accumulation in roots but at high salt concentration Pb accumulation decreased. The opposite was observed in the leaves where more Pb was accumulated at high salt concentration in soil. The toxic effect of Pb was visible only in the group treated with Pb without addition of NaCl into water for watering. The visible toxicity symptoms were connected only with high salinity. No excretion of Pb by salt glands was observed.     

Kinetics of soil microbial uptake of free amino acids

 Amino acids and proteins typically form the biggest input of organic-N into most soils and provide a readily available source of C and N for soil microorganisms. Amino acids can also be taken up directly by plant roots, providing an alternative source of available soil N. However, the degree to which plants can compete against the soil microbial population for amino acids in soil solution remains poorly understood. The aim of this study was to measure the rate of microbial uptake of three contrastingly charged ¹⁴C-labelled amino acids (glutamate^1–, glycine⁰, lysine^0.9+) over a wide concentration range (0.1–5 mM) and in two contrastingly managed soils varying in their degree of erosion, organic-C content and microbial biomass. Amino acid uptake was concentration dependent and conformed to a single Michaelis-Menten equation. The mean maximum amino acid uptake rate (V _max) for the non-eroded (control) soil (high organic-C, high biomass) was 0.13±0.02 mmol kg^–1 h^–1, while half maximal uptake occurred at a concentration (K _m) of 2.63±0.07 mM. Typically, V _max was fourfold lower and K _m twofold lower in the eroded soil (low available organic-C, low biomass) compared to the non-eroded (control) soil. Amino acid substrate concentration had little effect on the proportion of amino acid utilized in catabolic versus anabolic metabolism and was similar for both. While the results obtained here represent the summation of kinetics for a mixed soil population, they indicate that amino acid uptake is saturated at concentrations within the millimolar range. Because the affinity constants also were similar to those described for plant roots, we hypothesized that competition for amino acids between plants and microbes will be strong in soil but highly dependent upon the spatial distribution of roots and microbes in soil. Received: 2 March 2000     

铅胁迫下小花南芥与玉米间作对根系分泌物 有机酸的影响

为了揭示Pb胁迫对间作和单作的超累积植物和作物根系分泌低分子有机酸的影响,研究设置400 mg·L?1Pb胁迫,采用水培曝气法试验,以玉米和小花南芥单作为对照处理,研究Pb胁迫下玉米和小花南芥间作对植物根系形态、根系分泌有机酸及Pb吸收的影响。结果表明:与单作相比,间作小花南芥情况下,玉米根系分泌物检测到乳酸;玉米分根条数、根表面积和根密度与单作相比分别增加60%、15%和42%,地下部和地上部干重生物量分别增加108%和75%,玉米地下部Pb含量下降44%;与单作相比,间作玉米条件下,小花南芥根系分泌物检测到乙酸和乳酸,小花南芥根系分泌物量与单作相比增加103%~1 700%,小花南芥地下部和地上部Pb累积量分别比单作增加49%和75%,转运系数增加22%。相关分析结果表明,单作小花南芥只有地上部Pb累积量与草酸显著相关,而间作小花南芥地下部和地上部Pb累积量与草酸、柠檬酸和苹果酸显著相关。研究表明超富集植物小花南芥与玉米间作体系,根系分泌的有机酸改变了Pb在小花南芥和玉米体内的累积特征,促进超累积植物小花南芥累积Pb,减少农作物玉米植株体内Pb含量。Pb胁迫下超累积植物小花南芥与玉米间作是一种可行的修复模式。     

Comparative Study of Lead Accumulation in Different Organs of the Freshwater Crab <Emphasis Type="Italic">Zilchiopsis oronensis</Emphasis>

Lead (Pb) is known as an important aquatic contaminant with different toxic effects on various organisms. Until now, only few quantitative investigations have been published comparing Pb content in different organs of adult freshwater crabs. Their capacity to bioaccumulate other heavy metals is already known, and they can potentially transfer Pb to the terrestrial systems, as they are frequent trophic items of reptiles and birds, even humans. The objectives of this study were to assess Pb accumulation in the gills, carapace, digestive gland, and quela muscle of the freshwater crab Zilchiopsis oronensis, and to correlate bioaccumulation with morphometric data and sex. The crabs were manually caught in unpolluted ponds of the middle Paraná River alluvial valley (Santa Fe, Argentina). After the acclimation period, they were individually and randomly exposed per quadruplicate to three Pb experimental doses: 20, 40, and 80 mg Pb/L, in plastic cages during 15 days. After dissecting the crabs, the tissues were analyzed for lead in a Perkin Elmer Analyst 800 atomic absorption spectrometer. We found significant differences (p < 0.05) between the control and each one of the treatments but not between treatments (p > 0.05) and highly significant differences (p < 0.0001) between Pb concentration in organs. The Tukey posttest showed significant differences (p < 0.05) between gills–carapace, gills–digestive gland, and gills–quela muscle. The weight of the crabs only showed a negative correlation with Pb in the quela muscle (r = −0.53; p = 0.03). Pb in the carapace (but not in the other tissues) was positively correlated with the width (p = 0.571) and length (p = 0.616). Males accumulated more Pb than females, though not significantly. The present paper is aimed to contribute to our knowledge on Pb accumulation in freshwater crabs and select the better indicator organisms for biomonitoring.     

Chelate-enhanced phytoextraction and phytostabilization of lead-contaminated soils by carrot (Daucus carota)

The objective of this study was to study the influence of different ethylenediamine tetraacetate (EDTA), nitrilotriacetic acid (NTA) and oxalic acid (HOx) concentrations on tolerance and lead (Pb) accumulation capacity of carrot (Daucus carota). The results indicated that by increasing Pb, NTA and HOx concentrations in the soil, the shoot, taproot and capillary root dry matters increase effectively. In contrary, EDTA caused to reduce capillary roots biomass. EDTA was more effective than NTA and HOx in solubilizing soil Pb. The highest Pb content in shoots (342.2 ± 13.9 mg kg^?1) and taproots (301 ± 15.5 mg kg^?1) occurred in 10 mM EDTA, while it occurred for capillary roots (1620 ± 24.6 mg kg^?1) in 5 mM HOx, when the soil Pb concentration was 800 mg kg^?1. The obtained high phytoextraction and phytostabilization potentials were 1208 (±25.6) and 11.75 (±0.32) g Pb ha^?1 yr^?1 in 10 mmol EDTA kg^?1 soil and no chelate treatments, respectively. It may be concluded that chelate application increases Pb uptake by carrots. Consequently, this plant can be introduced as a hyperaccumulator to phytoextract and phytostabilize Pb from contaminated soils.     

续断菊与玉米间作的铅累积及根系低分子量有机酸分泌特征研究

为探明间作作物根系分泌低分子量有机酸对土壤重金属生物有效性的影响,采用矿区周边农田土壤进行室内盆栽试验,研究了云南本土超累积植物续断菊(Sonchus asper L. Hill)和玉米(Zea mays L.)间作下,植物生长、根系低分子量有机酸分泌量、根际土壤Pb提取形态以及植物Pb积累特点。结果表明:与单作相比,间作续断菊地上部和根部生物量、根长、根内径和根系体积均显著增加(P0.05);间作玉米根部生物量、根长、根内径和根系体积显著增加(P0.05)。柠檬酸、草酸是续断菊和玉米根系分泌的主要低分子量有机酸,间作导致续断菊根系低分子量有机酸的分泌量增加,玉米根系低分子量有机酸的分泌量降低。续断菊根际土壤生物有效态Pb含量增加85.2%(P0.05),而玉米根际土壤生物有效态Pb含量降低26.1%(P0.05)。续断菊体内Pb含量显著增加18.0%～43.2%(P0.05),富集系数提高26.0%,而转运系数降低42.0%;玉米地上部Pb含量显著降低24.3%(P0.05),转运系数降低43.1%。续断菊根系分泌的柠檬酸和草酸数量,均与土壤生物有效态Pb含量呈显著正相关,且土壤有效态Pb含量分别与续断菊地上部和根部的Pb含量呈显著正相关。表明间作增加了续断菊对Pb的吸收积累量,与间作体系植物根系分泌的低分子有机酸介导下的土壤有效态Pb含量增加密切相关。     

Hyper-spectral remote sensing to monitor vegetation stress

Background, aim, and scope  Vegetation stress diagnoses based on plant sampling and physiochemical analysis using traditional methods are commonly time-consuming, destructive and expensive. The measurement of field spectral reflectance is one basis of airborne or spaceborne remote sensing monitoring. Materials and methods  In this study, paddy plants were grown in the barrels evenly filled with 10.0 kg soil that was mixed respectively with 0, 2.5 × 207.2 and 5.0 × 207.2 mg Pb per 1,000 g soil. Rice canopy spectra were gathered by mobile hyper-spectral radiometer (ASD FieldSpec Pro FR, USA). Meanwhile, canopy leaves in the field-of-view (FOV) of spectroradiometer were collected and then prepared in the laboratory, (1) for chlorophyll measurement by Model 721 spectrophotometer, and (2) for Pb determination by atomic absorption spectrophotometer (SpectraAA-220FS). Results and discussion  Canopy spectral reflectance in the region of visible-to-near-infrared light (VNIR) increased, because ascended Pb concentration caused the decrease of canopy chlorophyll content. In the agro-ecosystem, however, heavy metal contamination is presented typically as mixture and their interactions strongly affect actually occurring effects. Normalized spectral absorption depth (D _n), and shifting distance (DS) of red edge position (REPs) revealed the differences in Pb concentration for canopy leaves, especially at the early tillering stage. Due to insufficient biomass of rice plants, the 30th day was not reliable enough for the selection of crucial growth stages. Some special sensitive bands might be omitted at the same time because of limited sample sets. Conclusions  Our initial experiments are still too few in the amounts of both metals and plants neither to build accurate prediction models nor to discuss the transformation from ground to air/spaceborne remote sensing. However, we are pleased to communicate that ground remote sensing measurements would provide reliable information for the estimation of Pb concentration in rice plants at the early tillering stage when proper features (such as DS and D _n) of reflectance spectra are applied. Recommendations and perspectives  Hyper-spectral remote sensing is a potential and promising technology for monitoring environmental stresses on agricultural vegetation. Further ground remote sensing experiments are necessary to evaluate the possibility of hyper-spectral reflectance spectroscopy in monitoring different kinds of metals’ stress on various plants.     

PHOTOSYNTHETIC ACCLIMATION AND DECREASED CHLOROPHYLL(A + B) CONCENTRATIONS OCCUR IN NITROGEN-SUFFICIENT TOBACCO LEAVES IN RESPONSE TO CARBON DIOXIDE ENRICHMENT

Effects of carbon dioxide (CO₂) enrichment on plant growth and on nitrogen partitioning were examined in tobacco (Nicotiana tabacum L. cv. ‘Samsun’). Dry matter, leaf area and specific leaf weight were unchanged (P > 0.05) by CO₂ enrichment. Total soluble protein, soluble amino acids and inorganic nitrate also were unaffected by CO₂ enrichment (P > 0.05). Leaf chlorophyll (a + b) levels decreased 13% (P ≤ 0.05) in response to CO₂ enrichment. The diurnal accumulation of soluble amino acids was delayed and the initial slope of the A/C _i response curve was decreased 14% in the elevated compared to the ambient CO₂ treatment. The above findings showed that CO₂ enrichment affected leaf chlorophyll levels, diurnal soluble amino acid metabolism and photosynthetic responses to low intercellular CO₂ concentrations even though the plants were nitrogen sufficient. Inadequate nitrogen fertility cannot explain all of the effects of CO₂ enrichment on photosynthesis by tobacco leaves.     

EFFECTS OF ZIRCONIUM ON THE GROWTH AND PHOTOSYNTHETIC PIGMENT COMPOSITION OF CHLORELLA PYRENOIDOSA GREEN ALGAE

The effects of zirconium (Zr) were investigated on the growth rate, dry matter accumulation, and elemental and photosynthetic pigment composition of Chlorella pyrenoidosa green algae. Algae were treated with 0.1–50 μM (≈ 0.009–4.561 mg dm^?3) of Zr; inorganic compounds (Zr oxychloride, Zr nitrate) and organic chelates (Zr ascorbate or Zr citrate) were applied. All Zr compounds displayed only a slight insignificant inhibitory effect on the growth rate of algae. Treatment of algae with 1 μM Zr (as Zr ascorbate, a water soluble pH stable chelate) slightly stimulated and 5–50 μM Zr slightly inhibited the dry matter accumulation of Chlorella. Zirconium concentration in the nutrient solution decreased rapidly during the algae propagation, and Chlorella cells accumulated significant amounts of Zr. In the case of 1 μM Zr (Zr ascorbate) treatment, 60.6 μg g^?1 Zr was found in the washed cells; after 50 μM Zr application this value was 441 μg g^?1 Zr. Zirconium treatment reduced the P, Mg, Cu, and Ti concentrations in algae cells, and the concentration of Fe, Mn, and partly Zn was enhanced. Chlorophyll a, chlorophyll b, xanthophyll, and carotenoid concentrations were equally reduced by 13–33% in Zr-treated cultures. Zirconium treatment changed the chlorophyll a:chlorophyll b ratio and caused appearance of several new chlorophyll derivatives in Chlorella.     

深色有隔内生真菌柱孢顶囊壳对玉米幼苗生长、光合作用及耐铅能力的影响

Dark septate endophytic (DSE) fungi are ubiquitous and cosmopolitan,and occur widely in association with plants in heavy metal stress environment.However,little is known about the effect of inoculation with DSE fungi on the host plant under heavy metal stress.In this study,Gaeumannomyces cylindrosporus,which was isolated from Pb-Zn mine tailings in China and had been proven to have high Pb tolerance,was inoculated onto the roots of maize (Zea mays L.) seedlings to study the effect of DSE on plant growth,photosynthesis,and the translocation and accumulation of Pb in plant under stress of different Pb concentrations.The growth indicators (height,basal diameter,root length,and biomass) of maize were detected.Chlorophyll content,photosynthetic characteristics (net photosynthetic rate,transpiration rate,stomatal conductance,and intercellular CO2 concentration),and chlorophyll fluorescence parameters in leaves of the inoculated and non-inoculated maize were also determined.Inoculation with G.cylindrosporus significantly increased height,basal diameter,root length,and biomass of maize seedlings under Pb stress.Colonization of G.cylindrosporus improved the efficiency of photosynthesis and altered the translocation and accumulation of Pb in the plants.Although inoculation with G.cylindrosporus increased Pb accumulation in host plants in comparison to non-inoculated plants,the translocation factor of Pb in plant body was significantly decreased.The results indicated that Pb was accumulated mainly in the root system of maize and the phytotoxicity of Pb to the aerial part of the plant was alleviated.The improvement of efficiency of photosynthesis and the decrease of translocation factor of Pb,caused by DSE fungal colonization,were efficient strategies to improve Pb tolerance of host plants.     

Impact of coastal wetland cultivation on microbial biomass, ammonia-oxidizing bacteria, gross N transformation and N2O and NO potential production

A ¹⁵N dilution experiment was carried out to investigate effects of cultivation on the gross N transformation rate in coastal wetland zone. Microbial community composition was estimated by phospholipid fatty acid (PLFA) analysis and abundance of soil ammonia-oxidizing bacteria (AOB) was quantified by real-time polymerase chain reaction (PCR). Soil salinity decreased significantly, while total N increased after coastal wetland was cultivated. Microbial biomass (total PLFA), bacterial biomass, fungal biomass, and actinomycete biomass of the native coastal wetland soils were significantly (p < 0.05) lower than those of the cultivated soils whereas AOB population size also significantly increased after coastal wetland cultivation. Multiple regression analysis showed that total PLFA biomass and soil total N (TN) explained 97% of the variation of gross N mineralization rate in the studied soils (gross mineralization rate = 0.179 total PLFA biomass + 5.828TN − 2.505, n = 16, p < 0.01). Gross nitrification rate increased by increasing the soil AOB population size and gross mineralization rate (M) (gross nitrification rate = 3.39AOB + 0.18 M − 0.075, R ² = 0.98, n = 16, p < 0.01). Management of salt discharge and mineral N fertilization during the cultivation of wetland soils might have changed composition of soil microflora and AOB population size, thus influencing mineralization and nitrification. Probably, the cultivation of coastal wetland soils increased the risk of N losses from soil through nitrate leaching and gas emission (e.g., N₂O and NO).     

Spatial changes of soil fungal and bacterial biomass from a sub-alpine coniferous forest to grassland in a humid, sub-tropical region

 Fungal and bacterial biomass were determined across a gradient from a forest to grassland in a sub-alpine region in central Taiwan. The respiration-inhibition and ergosterol methods for the evaluation of the microbial biomass were compared. Soil fungal and bacterial biomass both significantly decreased (P<0.05) with the shift of vegetation from forest to grassland. Fungal and bacterial respiration rates (evolved CO₂) were, respectively, 89.1 μl CO₂ g^–1 soil h^–1 and 55.1 μl CO₂ g^–1 soil h^–1 in the forest and 36.7 μl CO₂ g^–1 soil h^–1 and 35.7 μl CO₂ g^–1 soil h^–1 in the grassland surface soils (0–10 cm). The fungal ergosterol content in the surface soil decreased from the forest zone (108 μg g^–1) to the grassland zone (15.9 μg g^–1). A good correlation (R ²=0.90) was exhibited between the soil fungal ergosterol content and soil fungal CO₂ production (respiration) for all sampling sites. For the forest and grassland soil profiles, microbial biomass (respiration and ergosterol) declined dramatically with depth, ten- to 100-fold from the surface organic horizon to the deepest mineral horizon. With respect to fungal to bacterial ratios for the surface soil (0–10 cm), the forest zone had a significantly (P<0.05) higher ratio (1.65) than the grassland zone (1.05). However, there was no fungal to bacterial ratio trend from the surface horizon to the deeper mineral horizons of the soil profiles. Received: 30 March 2000     

Chemical properties and reactivity of manganese chelates and complexes in solution and soils

Commercial fertilizers containing synthetic manganese (Mn) chelates and complexes are currently used to alleviate Mn deficiency in crops. However, studies conducted on Mn sources in order to evaluate their behavior maintaining Mn soluble in nutrient solution and soil have not been done. In this work, representative commercial Mn fertilizers based on chelates and complexes were characterized and their chemical stability in solution and interaction with soils has been evaluated. Fertilizers studied were two ethylene diamine tetraacetic acid (EDTA) Mn chelates, one N‐(1,2‐dicarboxyethyl)‐D,L‐aspartic acid (IDHA) Mn chelate, two lignosulfonates, one carboxylate, one fulvate, one gluconate, and one heptagluconate‐based Mn complex. Characterization consisted of the determination of the soluble and chelated or complexed Mn, and the ligand identification by nuclear‐magnetic resonance (NMR). Stability study included batch experiments in Ca solution at different pH and three batch experiments with soil comparing with MnSO₄. Results indicate that most of the Mn fertilizers comply with the declared “soluble and chelated or complexed” metal content. At a usual pH range of calcareous soils (7.5–8.5), both chelates and complexes maintain more Mn in solution than MnSO₄ in the presence of Ca. Several factors affect the Mn remaining in solution after the interaction with the soil, especially, the soil‐to‐solution ratio. All chelates and complexes are better alternatives to the use of MnSO₄ in agronomical practices such as fertigation and soil application. Mn‐IDHA as chelate and Mn‐HGl or Mn‐Carb as complexes can be efficient, economical, and environmental friendly fertilizers for foliar application and hydroponic cultures. In soil application, Mn‐EDTA or Mn‐LS would be the best options. In this case, lignosulfonic acid represents a sustainable and low‐cost solution.     

Effects of applied urea and straw on various nitrogen fractions in two Chinese paddy soils with differing clay mineralogy

Combined application of synthetic nitrogen (N) fertilizers and organic materials can enhance soil quality, but little is known about the distribution of fertilizer N among different soil fractions after crop harvest. A pot experiment using ¹⁵N tracer was employed to address this question with three treatments, i.e., labeled urea-only (¹⁵NU), labeled urea + rice straw (¹⁵NU-S) and labeled rice straw + urea (¹⁵NS-U) applied to a Ferallic Cambisol (1:1 type soil clay mineral) and a Calcaric Fluvisol (2:1 clay mineral). Soil microbial biomass N, fixed ammonium (fixed NH₄⁺), exchangeable ammonium and soil organic N fractions by hydrolysis (6 N HCl) and their isotope abundance were determined after the rice harvest. Soil newly formed N in urea + straw (U-S) treatments (¹⁵NU-S, ¹⁵NS-U) was the sum of labeled urea-N in ¹⁵NU-S and labeled straw-N in ¹⁵NS-U. Compared with ¹⁵NU, U-S significantly (P < 0.05) increased the content and percentage of newly formed total soil N, acid insoluble N, amino acid N, and hydrolysable unknown N in both soils. In U-S treatment, straw amendment significantly (P < 0.05) reduced the content and percentage of newly formed fixed-NH₄⁺-N in Fluvisol as compared with ¹⁵NU treatments. Soil microbes contributed to the larger percentage of newly formed amino acid N (P < 0.01) in Cambisol as compared with Fluvisol. Fertilizer N in various soil fractions was therefore strongly affected by clay mineral type and microbes after the combined application of organic materials and synthetic N fertilizer.     

Alleviation of salt stress by arbuscular mycorrhizal in zucchini plants grown at low and high phosphorus concentration

With the aim of determining whether the arbuscular mycorrhizal (AM) inoculation would give an advantage to overcome salinity problems and if the phosphorus (P) concentration can profoundly influence zucchini (Cucurbita pepo L.) plant responses to AM, a greenhouse experiment was carried out with AM (+AM) and non-AM (−AM). Plants were grown in sand culture with two levels of salinity (1 and 35 mM NaCl, giving electrical conductivity values of 1.8 and 5.0 dS m⁻¹) and P (0.3 and 1 mM P) concentrations. The percentages of marketable yield and shoot biomass reduction caused by salinity were significantly lower in the plants grown at 0.3 mM P, compared to those grown at 1 mM P. However, even at high P concentration, the absolute value of yield and shoot biomass of +AM zucchini plants grown under saline conditions was higher than those grown at low P concentration. The +AM plants under saline conditions had higher leaf chlorophyll content and relative water content than −AM. Mycorrhizal zucchini plants grown under saline conditions had a higher concentration of K and lower Na concentration in leaf tissue compared to −AM plants. The P content of zucchini leaf tissue was similar for +AM and −AM treatments at both low and high P concentrations in the saline nutrient solution. The beneficial effects of AM on zucchini plants could be due to an improvement in water and nutritional status (high K and low Na accumulation).     

Evaluation of the Suitability of Sewage and Recycled Water for Irrigation of Ornamental Plants

The present study was conducted to evaluate the potential benefits and risks of the sewage water and recycled treated water on three ornamental plant species, including Umbrella plant (Cyperus alternifolius), Euonymus (Euonymus japonicas), and Dracaena (Cordyline terminalis). Plants in the pots were irrigated with equal volumes of water in 2-day intervals. Treatment plants were analyzed for sodium (Na), potassium (K), copper (Cu), iron (Fe), and lead (Pb) concentrations, in roots and shoots. The experiment was conducted by using a completely randomized design (CRD) with five replications. Data were analyzed using analysis of variance technique and least significance difference (LSD) test was applied at 5% probability level. Plants species performed better in sewage water after recycled water, in terms of growth, number of leaves, chlorophyll content, and leaf thickness, which proved sewage water accelerates the growth and development of ornamental foliage plants, but plants irrigated with this water exhibited greater concentration of Pb than other treatments.     

Effects of foliar spray of two kinds of zinc oxide on the growth and ion concentration of sunflower cultivars under salt stress

This study investigated the effects of foliar application of normal and nano-sized zinc oxide on the response of sunflower cultivars to salinity. Treatments included five cultivars (‘Alstar’, ‘Olsion’, ‘Yourflor’, ‘Hysun36’ and ‘Hysun33’), two salinity levels [0 and 100 mM sodium chloride (NaCl)], and three levels of fertilizer application. Fertilizer treatments were the foliar application of normal and nano-sized zinc oxide (ZnO). Foliar application of ZnO in either forms increased leaf area, shoot dry weight, net carbon dioxide (CO₂) assimilation rate (A), sub-stomatal CO₂ concentration (Ci), chlorophyll content, Fv/Fm, and Zn content and decreased Na content in leaves. The extent of increase in chlorophyll content, Fv/Fm and shoot weight was greater as nano-sized ZnO was applied to the normal form. The results show that the nano-sized particles of ZnO compared to normal form has greater effect on biomass production of sunflower plants.     

Na+与Cl–浓度平衡供应促进小白菜干物质积累及营养品质提升

  【目的】  适宜的Na+与Cl–浓度均有利于植物的生长,但Na+和Cl–哪个起主导作用,以及二者之间的平衡关系对其有益作用的影响尚不清楚。因此,拟通过本研究为低浓度氯化钠在生产中的应用提供理论依据。  【方法】  采用盆栽试验培养小白菜(Brassica campestris L. ssp. chinensis var. communis Tsen et Lee),在小白菜长到3叶1心时进行叶面喷施处理。以NaCl为基础,设置了[Na+]<[Cl–] (A)、[Na+]＝[Cl–] (B)和[Na+]>[Cl–] (C) 3组处理。B组平衡态的3个处理的[Na+]∶[Cl–]的浓度(mmol/L)比为6∶6 (B₁)、12∶12 (B₂)、18∶18 (B₃);A组非平衡态的3个处理为0∶6 (A₁)、6∶12 (A₂)、12∶18 (A₃);C组非平衡态的3个处理的比值是6∶0 (C₁)、12∶6 (C₂)、18∶12 (C₃),以无离子水为对照CK,每日喷施一次,连续处理21天。停止喷施后,取样观测叶片组织结构,测定植株干鲜物质量、叶片光合活性以及游离氨基酸含量。  【结果】  无论[Na+]和[Cl–]是平衡还是非平衡状态,喷施处理均显著提高了小白菜的干鲜物质积累量和叶片光合活性。与CK相比,3个[Na+]、[Cl–]等浓度供给处理均显著增加了小白菜植株干、鲜生物量,显著增加了植株游离氨基酸含量,增加了叶面积尤其是中上位叶面积,促生效果均以B₂ 处理最佳,植株干、鲜生物量分别比CK增加了35.1%和43.7%,叶面积增加了33.4%。在非平衡状态中,有Cl–无Na+时有利于含水量增加,有Na+无Cl–时有利于干物质累积,且表现出Na+和Cl–均有利于含水量增加,Na+比Cl–更有利于游离氨基酸累积([Na+]>[Cl–]时,增加52.6%),Cl–比Na+更有利于干物质累积和光合速率([Na+]<[Cl–]时,增加17.3%)以及气孔导度([Na+]<[Cl–]时,增加145.3%)增加的现象。2因素主体间效应检验显示,小白菜的植株干鲜物质和营养物质累积、叶面积和比叶重、叶片光合气体交换活性,既受Na+、Cl–单独离子效应的影响,又受Na+与Cl–交互效应的影响。  【结论】  叶面喷施[Na+]与[Cl–]平衡与否都对小白菜的生长、干物质累积、含水量增加和叶片光合活性具有促进效应。但以12 mmol/L NaCl的生长促进效应更优,其主要表现为叶面积的扩展促使植株干物质累积。     

Roles of glycine betaine in mitigating deleterious effect of salt stress on lettuce (Lactuca sativa L.)

This study was conducted to evaluate the roles of glycine betaine (GB) in mitigating deleterious effect of salt stress on lettuce. Lettuce plants were subjected to two salinity (0 and 100 mmol l^?1 NaCl) and four GB levels (0, 5, 10, 25 mmol l^?1). Salinity resulted in a remarkable decrease in growth parameters, relative leaf water content and stomatal conductance. Plants subjected to salt stress exhibited an increase in membrane permeability (MP), lipid peroxidation (MDA), leaf chlorophyll reading value, H₂O₂ and sugar content. Exogenous foliar applications of GB reduced MP, MDA and H₂O₂ content in salt-stressed lettuce plants. Salt stress increased Na and generally decreased other nutrient elements. GB reduced Na accumulation, but significantly increased other element contents under salinity conditions. The study showed that gibberellic acid (GA) and salicylic acid (SA) content in salt-stressed plants were lower than those of nonstressed plants. However, salinity conditions generally increased the abscisic acid content. GB treatments elevated the concentrations of GA, SA and indole acetic acid (IAA) at especially 10 and 25 mmol l^?1 GB under salt stress conditions. It could be concluded that exogenous GB applications could ameliorate the harmful effects of salt stress in lettuce.     

The individual and combined effects of ozone and simulated acid rain on chlorophyll contents,carbon allocation and biomass accumulation of armand pine seedlings

The seedlings of armand pine (Pinus armand Franch.) were applied to exposure, alone or in combination, to charcoal filtered air (CF) or ozone (O₃) at 300±15 nl/l(ppb) for 8 h a day, 6 days a week, and simulated rain of pH 6.8, 3.0 or 2.3, six times a week, alone and in combination, for 14 weeks from June 15 to September 20, 1993. No significant interactive effects of O₃ and simulated acid rain were observed on chlorophyll contents, carbon allocation and biomass accumulation of the seedlings in the present study. The O₃ caused reductions in biomass accumulation of whole-plant and below-ground parts, but not that of above-ground parts without an acute visible foliar injury. At the same time, the O₃ reduced R/S ratio, but raised F/C ratio. Therefore, O₃ also altered carbon allocation pattern. On the other hand, chlorophyll contents were increased by simulated acid rain, but other determined parameters were not altered.