Phytoextraction of Zinc by Indian Mustard and Tall Fescue

Abstract

This experiment evaluated the capacity of two species, Indian mustard (Brassica juncea Czern.) and tall fescue (Festuca arundinacea Schreb.) to extract zinc (Zn) from soils. Also, this experiment focused on using nitrogen (N) fertilizers to increase the phytoextraction of Zn. Two soils of the Hadley series (Typic Udifluvents) were studied. A treatment array of Zn concentrations in soils was supplied as zinc sulfate. Nitrogen was supplied at 200 mg N/kg of soil as calcium nitrate, urea, or compost. Two successive plantings of Indian mustard in the same media were grown until flowering and harvested. Fescue was grown from seeding to a height of 15 cm, harvested, grown again in the same media to a height of 15 cm, and harvested again. After the second harvests of Indian mustard and fescue, soil samples were taken for analysis of extracts with water and with Morgan's solution. Indian mustard was grown with Zn additions ranging from 0 to 100 mg/kg soil. The shoot mass of Indian mustard in both harvests increased to a soil‐Zn level of 25 mg/kg and then decreased. Although growth decreased as the soil‐Zn levels increased beyond 25 mg/kg, Zn concentration and total accumulation increased linearly as the soil‐Zn levels increased. Zinc concentration and accumulation in Indian mustard were highest in soils amended with urea and were lowest in soils with no fertilizer. Fescue was grown with Zn additions ranging from 0 to 1000 mg/kg soil. The shoot mass of fescue increased to a soil‐Zn level of 125 mg/kg (harvest 1) or 250 mg/kg (harvest 2) and then decreased as the soil‐Zn levels increased. Concentration and accumulation of Zn in fescue increased linearly as the soil‐Zn levels increased. Zinc concentration and accumulation were highest in fescue grown in soils amended with urea and lowest in soils with no fertilizer. The highest accumulation of Zn in fescue (3800 mg/pot) occurred at 1000 mg Zn/kg soil. Highest concentrations of soil Zn were extracted with Morgan's solution or water from soils amended with urea, regardless of the species grown in the soils. Lowest concentrations of Zn were extracted from soils with no fertilizer added, regardless of extract or species. In general, if fertilizers (calcium nitrate, urea, or compost) were added to the soils, the pH decreased. Fescue was easy to grow, tolerated much higher soil‐Zn levels than Indian mustard in this research, and could be a species useful for phytoextraction of Zn.     

Influence of Ammonium and Nitrate Nutrition on Plant Growth and Zinc Accumulation by Indian Mustard

ABSTRACT

The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH₄ ⁺ to NO₃ ^? to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH₄ ⁺ to NO₃ ^? on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L^?1) in combination with six N treatments with different molar percentage ratios of NH₄ ⁺ to NO₃ ^? (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L^?1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L^?1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO₃ ^?. Supplying high proportions of NO₃ ^? in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH₄ ⁺ (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH₄ ⁺ in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant^?1, if plants received 10% of the total N as NH₄ ⁺ and 90% as NO₃ ^?.     

Phytoextraction Potential of Indian Mustard at Various Levels of Zinc Exposure

ABSTRACT

Indian mustard (Brassica juncea Czern.) has the potential to extract zinc (Zn) and other metals from contaminated soils, but the potential to accumulate metals at different levels of exposure is not well documented. The objectives of this research were to assess plant growth and Zn accumulation for different metal-accumulating accessions of Indian mustard grown with various Zn concentrations. In the experiment, three accessions of Indian mustard (426308, 182921, and 211000) were supplied with 12 levels of Zn (ranging from 0.0 to 7.0 mg L^?1) for three weeks in solution culture. Accession 426308 had a greater capacity for dry-mass accumulation than the others, but differences among accessions lessened as the concentration of Zn in solution increased. Accessions did not differ in Zn concentrations in shoots, but accession 426308 had a greater potential to accumulate Zn than the other accessions. Elevating the Zn supply in solutions had a limited effect on increasing the total Zn accumulation of shoots. Plants suffered Zn-induced iron (Fe) deficiency if the Zn concentration in solution exceeded 2.0 mg Zn L^?1. The level of Zn tolerance of Indian mustard accessions was: 211000 > 182921 > 426308. Maximum Zn accumulation in shoots was approximately 5.0 mg Zn per plant. The phytoextraction potential of Indian mustard may be limited under Zn-contaminated conditions by nutrient disorders and toxic effects of Zn that suppress growth.     

微生物对土壤Cd Pb和Zn生物有效性的影响研究

采用土壤盆栽模拟试验方法,研究了接种不同微生物对重金属富集植物——印度芥菜修复土壤中Cd、Pb、Zn的作用效果。结果表明,接入菌株JA27、JC55、JC40不仅显著促进植物的生长,提高印度芥菜的生物量,降低了土壤pH,并且对土壤Cd、Pb、Zn产生活化作用,使土壤Cd、Pb、Zn有效态含量显著增加,增强印度芥菜对土壤Cd、Pb、Zn吸收量,显著提高了富集植物的修复效果。以上3个处理使印度芥菜地上部Cd、Pb、Zn吸收量分别提高了117%～137%、37%～62%、9%～15.1%。接种JB37对土壤Cd、Pb、Zn产生钝化作用,并且抑制印度芥菜对土壤Cd、Pb、Zn的吸收。JB37处理印度芥菜地上部Pb、Zn吸收量分别降低了72.5%、27%,对Cd吸收量无显著影响。     

Interactive Effects of Lanthanum and Cadmium on Plant Growth and Mineral Element Uptake in Crisped-Leaf Mustard Under Hydroponic Conditions

Plant growth and mineral element accumulation in Brassica juncea var. crispifolia (crisped-leaf mustard) under exposure to lanthanum (La) and cadmium (Cd) were studied by employing a hydroponic experiment with a complete two-factorial design. Four levels of La (0.05–5.0 mg L^?1) and two levels of Cd (1.0 and 10.0 mg L^?1) were used in this experiment. Lanthanum did not improve plant growth in this experiment. Addition of La (≥ 1.0 mg L^?1) or Cd (≥ 10 mg L^?1) to the solution inhibited root elongation. Lanthanum treatments reduced accumulations of iron (Fe), manganese (Mn), and zinc (Zn) in roots, and Mn in shoots. Lanthanum at ≥ 1.0 mg L^?1 limited the Cd translocation from roots to shoots and thus decreased the accumulation of Cd in shoots. Cadmium had no influence on La accumulations in roots, but inhibited the accumulation of La in shoots. The study results suggest that applications of rare earth elements in vegetables would be potentially risky to human health.     

Arsenic and Cadmium Phytoextraction Potential of Crambe Compared with Indian Mustard

ABSTRACT

The ability to tolerate and accumulate arsenic (As) and cadmium (Cd) was compared between Brassica juncea (Indian mustard) and Crambe abyssinica (Hochst.) (Crambe or Abyssinian mustard). Plants were grown hydroponically and treated with 70 μM sodium arsenate or 50 μ M cadmium chloride for two weeks. When nutrients were omitted during the As treatment, leaves of C. abyssinica accumulated an average of 140 mg As kg^?1, compared with 34 mg kg^?1 for B. juncea. When quarter-strength Hoagland's nutrient solution was provided during As treatment, leaves of C. abyssinica accumulated an average of 270 mg As kg^?1, compared with 13 mg kg^?1 for B. juncea. Cadmium accumulation on a dry-weight basis was approximately two times greater in shoots of B. juncea. Shoot biomass production in the presence or absence of metals was greatest for C. abyssinica. Because of its larger biomass and more efficient accumulation of As, C. abyssinica should be considered for use in phytoremediation research.     

Kinetics of Zinc Uptake and Anatomy of Roots and Leaves of Coffee Trees as Affected by Zinc Nutrition

Abstract

The influence of silicon (Si) (2.5 mM), sodium chloride (NaCl) (100 mM), and Si (2.5 mM) + NaCl (97.5 mM) supply on chlorophyll content, chlorophyll fluorescence, the concentration of malondialdehyde (MDA), H₂O₂ level, and activities of superoxide dismutase (SOD; E.C.1.15.1.1.), ascorbate peroxidase (APx; E.C.1.11.1.11.), catalase (CAT; E.C.1.11.1.6.), guaiacol peroxidase (G-POD; E.C.1.11.1.7.) enzymes, and protein content were studied in tomato (Lycopersicon esculentum Mill c.v.) leaves over 10-day and 27-day periods. The results indicated that silicon partially offset the negative impacts of NaCl stress with increased the tolerance of tomato plants to NaCl salinity by raising SOD and CAT activities, chlorophyll content, and photochemical efficiency of PSII. Salt stress decreased SOD and CAT activities and soluble protein content in the leaves. However, addition of silicon to the nutrient solution enhanced SOD and CAT activities and protein content in tomato leaves under salt stress. In contrast, salt stress slightly promoted APx activity and considerably increased H₂O₂ level and MDA concentration and Si addition slightly decreased APx activity and significantly reduced H₂O₂ level and MDA concentration in the leaves of salt-treated plants. G-POD activity was slightly decreased by addition of salt and Si. Enhanced activities of SOD and CAT by Si addition may protect the plant tissues from oxidative damage induced by salt, thus mitigating salt toxicity and improving the growth of tomato plants. These results confirm that the scavenging system forms the primary defense line in protecting oxidative damage under stress in crop plants.     

蚯蚓对印度芥菜修复Zn、Pb污染土壤的影响

以褐土为供试土壤,分别加入不同浓度梯度Zn2+(0,100,200,400 mg kg^-1)或Pb2+(0,200,400,800 mg kg^-1)模拟土壤污染,设置添加蚯蚓与不添加蚯蚓处理,通过盆栽实验,研究蚯蚓对印度芥菜生长量和重金属吸收量的影响,旨在探讨蚯蚓在植物-土壤系统中影响重金属迁移转化的作用机理,为蚯蚓在植物修复技术的实践与完善提供理论参考。结果表明:(1)在Zn、Pb污染土壤中,蚯蚓生长率分别降低3%～24%、6%～29%;(2)蚯蚓活动可以降低土壤的pH,显著增加土壤中Zn的有效态含量;(3)蚯蚓活动显著增加了印度芥菜地上部生物量(22.6%～88.6%鲜重,31.3%～122%干重)和印度芥菜地上部Zn的浓度及Zn和Pb的吸收量。印度芥菜地上部重金属浓度和吸收量与土壤中DTPA提取态含量呈极显著正相关(P <0.01),与土壤pH呈负相关。(4)蚯蚓对重金属的活化和对植物生长的促进是解决植物修复瓶颈问题的有效手段。     

锌对不同基因型玉米幼苗光合特性及锌积累的影响

为探究不同基因型玉米幼苗对锌敏感性差异,以玉米杂交品种天农九(TN9)和信玉9(XY9)为材料,研究不同Zn浓度(0.00、0.01、0.1、1.0、10.0、100μmol·L-1)对叶片光合色素含量、光合作用参数及叶绿素荧光特性的影响。结果表明,玉米最适生长锌浓度为0.1~1μmol·L-1,低锌(0~0.01μmol·L-1)和高锌(10~100μmol·L-1)条件均对不同基因型玉米幼苗的生长产生抑制作用,其中XY9在低锌及高锌胁迫下光合参数及光合色素含量降幅显著,从而导致其植株长势和干物质积累等对锌浓度的动态响应更为强烈,而TN9则对低锌及高锌环境具有较强的适应性。同时,随着锌处理浓度的不断升高,玉米植株中锌含量和积累量均逐渐升高,锌利用率则逐渐降低,其中XY9植株锌积累量低于TN9,而锌利用率则高于TN9;相比于不敏感型品种(TN9),敏感型品种(XY9)对锌的吸收、积累和利用受锌浓度变化的影响更为明显。本研究为植物锌高效利用研究提供理论基础。     

Effects of Nitrogen and Sulfur on Total Phenolics and Antioxidant Activity in Two Genotypes of Leaf Mustard

Leaf mustard (Brassica juncea Coss) is widely used for both fresh and processed markets in southern China. It contains high nutritional and medicinal compounds, which are important for maintaining optimum health. The objective of this study was to determine the influence of nitrogen (N) and sulfur (S) nutrition on total phenolics and antioxidant activity in two genotypes of leaf mustard (cvs. ‘Xuelihong’ and ‘Zhujie’). Plants were greenhouse-grown using nutrient solutions with two levels of nitrogen (10 and 25 mM) and three levels of sulfur (0.5, 1, and 2 mM). Total phenolic concentrations were considerably decreased by increasing nitrogen supply, whereas increased by increasing sulfur supply. Total phenolic concentrations in cv ‘Zhujie’ was higher than in cv ‘Xuelihong’. Three assays including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, β -carotene bleaching (BCB), and ferric reducing antioxidant power (FRAP) were used to evaluate antioxidant activity. Increasing nitrogen supply reduced DPPH radical scavenging activity and FRAP value, but increased antioxidant activity using BCB assay. Increasing sulfur supply increased antioxidant activity with all three tests. The effects of genotype on DPPH radical scavenging activity and FRAP value were not significant, however, antioxidant activity using BCB assay was significantly higher in cv ‘Zhujie’ than in cv ‘Xuelihong’. A significantly positive correlation was found between DPPH radical scavenging activity and total phenolic concentrations in two genotypes, FRAP value and total phenolic concentrations in cv ‘Xuelihong’.     

Alleviation of Multinutrient Deficiency for Productivity Enhancement of Rain-Fed Soybean and Finger Millet in the Semi-arid Region of India

Soil nutrient contents were determined in 802 surface soil samples (0–15 cm deep) collected from farmers' fields that support extensive cultivation of soybean (Glycine max L.) and finger millet (Eleusine coracana G.), spread across three districts, in the semi-arid regions of Karnataka, India. Following soil analysis, on-farm crop trials were conducted during 2005–2007 to study the crop response to the soil application of nitrogen (N), phosphorus (P), sulfur (S), boron (B), and zinc (Zn) fertilizers. Analyses of soil samples revealed that 4–83% fields were deficient in N, 34–65% in P, 83–93% in extractable S, 53–96% in B, and 34–88% of farmers' fields were deficient in Zn. On-farm trials conducted during the three rainy seasons (2005, 2006, and 2007) significantly (P ≤ 0.05) enhanced crop productivity indices such as yields of grain, stover, and total biomass in soybean and finger millet crops. Integrated management of deficient nutrients in finger millet and soybean crops significantly enhanced the grain and straw uptake of N, P, K, S, and Zn.     

Zinc Deficiency in Selected Cultivars of Wheat and Barley as Tested in Solution Culture

Abstract

The relative zinc (Zn) efficiencies of 33 wheat and 3 barley cultivars were determined by growing them in chelate‐buffered culture solutions. Zn efficiency, determined by growth in a Zn‐deficient solution relative to that in a medium containing an adequate concentration of Zn, was found to vary between 10% and 63% among the cultivars tested. Out of the 36 cultivars tested, 12 proved to be Zn efficient, 10 were Zn inefficient, and the remaining 14 varieties were classed as intermediate. The most Zn‐efficient cultivars included Bakhtawar, Gatcher S61, Wilgoyne, and Madrigal, and the most Zn inefficient included Durati, Songlen, Excalibur, and Chakwal‐86. Zn‐efficient cultivars accumulated greater amounts of Zn in their shoots than inefficient cultivars, but the correlation between shoot Zn and shoot dry matter production was poor. All the cultivars accumulated higher concentrations of iron (Fe), copper (Cu), manganese (Mn), and phosphorus (P) at deficient levels of Zn, compared with adequate Zn concentrations. The Zn‐inefficient cultivars accumulated higher concentrations of these other elements compared to efficient cultivars.     

2种优势植物对不同粒径炼锌废渣团聚体养分及重金属赋存形态分布的影响

为评价土法炼锌废渣堆场上自然着生的优势植物对废渣团聚体中重金属的控制效应及生态修复效果,以废渣堆场上已自然定居且生长茂盛的本土植物土荆芥(Chenopodium ambrosioides L.)和大叶醉鱼草(Buddleja davidii Franch.)为研究对象,以未经修复的空白废渣为对照,分析这2种优势植物对根际、非根际废渣内不同粒径团聚体中主要养分(氮、磷、有机质)和主要重金属(Cu、Pb、Zn、Cd)赋存形态及含量分布的影响。结果表明:土法炼锌废渣堆场上自然着生的2种优势植物对根际与非根际不同粒径炼锌废渣的主要养分含量具有显著影响,且不同种类植物参与对根际与非根际废渣中有机质的贡献明显不同。养分在粒径<1 mm的团聚体废渣中分布含量较高,除大叶醉鱼草非根际废渣中的总氮含量低于对照废渣外,植物影响下的各粒径团聚体中的养分含量总体高于对照废渣。优势植物生长明显影响炼锌废渣中Cu、Pb、Zn、Cd等主要重金属在不同粒径废渣中的含量分布及赋存特征,Cu和Cd主要分布在粒径<0.25,0.25~0.5,0.5~1 mm团聚体中,Zn主要分布在粒径<0.25,2~5 mm团聚体中,Pb则在0.25~5 mm的4种不同粒径团聚体中含量分别达最高;且其降低了各粒径废渣团聚体中Cu、Pb含量,对粒径>5 mm团聚体中的Cd含量有一定的提高作用,其中,2种优势植物影响下的粒径<5 mm团聚体中的酸可溶解态Cu、Pb、Zn的比例明显降低,而残渣态Zn和酸可溶解态Cd的比例有所提升。主成分分析结果表明,2种优势植物对根际和非根际粒径<5 mm团聚体中的养分、Zn全量及酸可溶解态Cd含量贡献率高,但对粒径>5 mm团聚体中的养分影响不大。综上,自然定居且繁茂生长的土荆芥和大叶醉鱼草可显著改善铅锌冶炼废渣中的养分状况,同时可有效减小废渣中重金属Cu、Pb、Zn对环境生态的潜在风险,开展铅锌冶炼废渣堆场水土保持及生态修复相关工作时可优选这2种植物作为先锋植物。     

Effects of Green Manures and Zinc Fertilizer Sources on DTPA-Extractable Zinc in Soil and Zinc Content in Basmati Rice Plants at Different Growth Stages

Rice is very sensitive to low zinc(Zn) supply in submerged paddy soils and Zn deficiency is one of the major limiting factors in determining rice production in India. A field experiment was conducted during the summer-rainy seasons of 2009 and 2010 at the research farm of the Indian Agricultural Research Institute, New Delhi, to determine the effects of summer green manure crops and Zn fertilizers on diethylenetriaminepentaacetic acid(DTPA)-extractable(available) Zn concentration in soil and total Zn content in Basmati rice cultivar Pusa Basmati 1 at periodic intervals. Summer green manure crops included Sesbania aculeata(Dhaincha),Crotalaria juncea(Sunhemp), and Vigna unguiculata(Cowpea) and the Zn fertilizers used were ethylenediaminetetraacetic acid(EDTA)-chelated Zn, ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnO, and ZnSO_4·7H_2O + ZnO. Beneficial effects of summer green manure crops and Zn fertilizers on DTPA-extractable Zn concentration in soil and total Zn content in dry matter of Basmati rice at periodic intervals were observed, with significant increases in all the determined parameters, in comparison with those in the control(no Zn application or summer fallow). The rate of increase varied among summer green manure crops and Zn fertilizers during both years. Among the summer green manures, incorporation of S. aculeata led to a significant increase in mean Zn content in Basmati rice grain and straw when compared with C. juncea, V. unguiculata, and summer fallow treatments. Among the Zn fertilizers, significant increases in Zn content in Basmati rice dry matter and DTPA-extractable Zn concentration in soil during various growth stages of the plant were recorded with EDTA-chelated Zn application, followed by the application of ZnSO_4·7H_2O, ZnSO_4·H_2O, ZnSO_4·7H_2O + ZnO, ZnO,and no Zn. The highest mean Zn content in Basmati rice grain and straw was recorded with EDTA-chelated Zn application in 2009 and 2010, respectively. The application of ZnSO_4·7H_2O was the second best treatment after EDTA-chelated Zn; however, it was statistically inferior to EDTA-chelated Zn. The lowest values were recorded with the control(no Zn application) during both years of study. The amount of Zn concentration in soil was found to be significantly positively correlated with the Zn content in Basmati rice dry matter during both years. Significantly higher levels of residual fertility in soil after the harvest of Basmati rice were observed with application of EDTA-chelated Zn and incorporation of S. aculeata when compared with those of other Zn sources and summer green manures.     

胶质芽孢杆菌对印度芥菜富集土壤Cd的效果

通过灭菌土培试验研究分别接种0,12.5,25,37.5,50,62.5ml/盆活菌浓度为1×109 cfu/ml的胶质芽孢杆菌,对印度芥菜修复Cd污染土壤的作用效果。结果表明,接入胶质芽孢杆菌菌液25ml/盆时,植物地上、地下部分对Cd的提取量分别为其他接种量的1.10～1.48倍,1.32～1.77倍。以不种印度芥菜作为对照,种印度芥菜处理的土壤Cd随着时间的变化去除效果有所不同,接菌后14d左右土壤Cd含量最低,收获时土壤Cd去除率可达到20%,显著提高其植物修复效果。同时,不同浓度的胶质芽孢杆菌均可以促进富集植物的生长,印度芥菜地上、地下部分生物量分别提高3%～16%,4%～61%。综上,胶质芽孢杆菌不但可以提高污染土壤中Cd的生物有效性,而且可明显促进超富集植物生长。     

华北冬绿肥作物二月兰的营养特征研究

二月兰可作为冬季绿肥作物引入华北地区农田种植,与春玉米等作物形成良好的粮肥复种体系,在华北地区有着广阔前景.本试验调查分析了二月兰从返青到成熟的养分含量及累积状况,结果表明,二月兰植株体的养分含量较高,盛花期其干物质氮、磷、钾含量分别为2.99％、0.42％和2.99％,且产量较高.二月兰对氮、钾的累积量大,对磷的累积量较小.盛花期二月兰的养分已累计完成了总量的86.3％～94.0％,是进行翻压的最适宜时期.二月兰的养分累积过程符合Logistic方程y=k/(1 +ae-bx),氮、磷、钾最大累积速率出现的先后顺序为磷最早、氮次之、钾最晚.     

Effects of Iron and Zinc Fertilizers on the Accumulation of Fe And Zn Ions in Potato Tubers

The aim of this study was the evaluation of the methods to increase the yield of potato and the accumulation of iron (Fe) and zinc (Zn) in response to iron and zinc fertilizers. In these studies, ‘Marfona’ potato (Solanum tuberosum) cultivar was used in a statistical factorial design experiment with three factors: methods of fertilizer application (2 levels of spray and one level by irrigation), kind of fertilizers (iron and zinc) and levels of fertilizer, (0, 1, 2, and 3 mg L^?1). Results showed that iron and zinc fertilizers increased the tubers weight and the tubers number weight^?1 ratio (P < 0.01). Also, results showed that the effects of Fe and Zn fertilizers application in irrigation water was more significant (P < 0.01) than by spray application. In addition, application of Fe and Zn fertilizers resulted in higher concentrations of these ions in the harvested tubers improving their nutritional values.     

Zinc accumulation in lettuce cultivars grown with organic or chemical based nutritional regimes

This study determined the potential to increase Zn density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management. Organic fertilizer and Hoagland and Arnon no.1 solution factored with three zinc (Zn) levels provided as zinc sulfate (ZnSO₄) were the fertilizer regimes in a greenhouse experiment. Modern cultivars had a 32% higher fresh head weight than heritage cultivars, but each accumulated the same Zn concentration (65 mg kg^?1 dry wt). Butterhead phenotypes had a 38% lower yield than loose-leaf and had the highest Zn concentration (78 mg kg^?1 dry wt) followed by romaine (66 mg kg^?1 dry wt) and loose-leaf (53 mg kg^?1 dry wt). Concentration of Zn did not differ between fertility regimes, being about 66 mg kg^?1 dry wt with each regime. Differences in Zn concentrations were significant among individual cultivars with ranges from 42 mg g^?1 dry wt to 91 mg kg^?1 dry wt. ‘Tom Thumb’, ‘Adriana’, ‘Claremont’, and ‘Focea’ were the top in cultivar ranking, with mean Zn concentration of 63 mg kg^?1 dry wt. The results signify that selection of cultivars may be utilized to increase Zn accumulation in lettuce but that nutritional regimes had little effect on accumulation.     

Effects of Iron Deficiency on Thylakoid Membrane Structure and Composition in the Alga Dunaliella salina

Abstract

The unicellular green alga Dunaliella was previously proposed as a model photosynthetic organism for adaptation to iron deficiency. The purpose of this study was to find out how iron limitation affects the structure and composition of the photosynthetic system of Dunaliella salina. Iron deprivation did not retard proliferation of D. salina cells, but was associated with a decrease in cell volume and chlorophyll content, and with a four‐fold reduction in iron content and a two‐fold increase in Cu content. Electron microscopic analysis revealed shrinkage of the chloroplast and decrease in stacked thylakoid membranes. Measurements of chlorophyll fluorescence induction in the presence of DCMU and of 77 K chlorophyll fluorescence emission spectra indicated gross changes in the photosynthetic efficiency of reaction centers and in the organization of their associated light harvesting antenna. Differential analysis of protein composition led to the identification of a major thylakoid membrane protein (Tidi), that was specifically induced under iron deprivation. Partial sequencing suggests that Tidi is a novel type of a chlorophyll a/b binding protein. These results clearly show that iron limitation is associated with extensive reorganization of the photosynthetic system in Dunaliella.     

镉胁迫下磷供应对芥菜生长和镉吸收的影响

采用土培和水培试验,研究了镉胁迫下磷供应对芥菜生长和镉吸收的影响。土培试验表明:施磷可以提高镉胁迫下小叶芥菜和雪里蕻种子的发芽率,提高小叶芥菜的生物量,而对雪里蕻生物量影响不大;施磷可以减少土壤中有效态镉含量,明显降低植株体内镉含量;植株体内的全磷含量随外加磷浓度的提高而显著增加。水培结果表明:镉胁迫下,磷供应对雪里蕻植株生物量影响不大;随着磷供应水平的增加,植株体内的全磷含量明显增加,但植株地上部镉、锌、钙、镁、锰等元素的含量明显降低。