Zinc toxicity‐induced variation of mineral element composition in hydroponically grown bush bean plants

Bush bean plants (Phaseolus vulgaris L. cv Contender) were grown for twenty days in nutrient solution (pH=5), containing 0.13, 0.3, 0.5 or 0.75 mg 1^‐1 Zn as ZnSO₄‐7H₂O. The plant yield decreased linearly with the increase of the Zn concentration supplied. The phytotoxic threshold content (for 10% growth reduction) was about 486, 242, 95 and 134^‐ μg Zn g^‐1 for roots, steins, mature primary and trifoliate leaves, and developing leaves, respectively. High inverse correlation coefficients with the Zh concentration supplied were found for the Mn content of all organs, for the P content of roots, and for the Cu and Ca contents of developing leaves. Significant positive relations were found for the Fe, Zn and Cu contents in roots and for the Zn con‐ tents in stems and fully expanded leaves. The ratios of the mineral contents between organs suggest inhibition of uptake of Mn and P, and inhibition of translocation of Fe, Cu and Ca. The relation between dry weight decrease and Zn‐induced nutrient content disorders were discussed.     

Responses of cucumber grown in recirculating nutrient solution to gradual Mn and Zn accumulation in the root zone owing to excessive supply via the irrigation water

A standard and a high manganese (Mn) level (10 and 160 μM) were combined with a standard and a high zinc (Zn) level (4 and 64 μM) in the nutrient solution supplied to cucumber in closed‐cycle hydroponic units to compensate for nutrient uptake. The concentrations of all nutrients except Mn and Zn were identical in all treatments. The objectives of the experiment were to establish critical Zn and Mn levels in both nutrient solutions and leaves of cucumber grown hydroponically, to assess the impact of gradual Zn and/or Mn accumulation in the external solution on nutrient uptake and gas exchange, and to find whether Mn and Zn have additive effects when the levels of both ions are excessively high in the root zone. The first symptoms of Mn and Zn toxicity appeared when the concentrations of Mn and Zn in the leaves of cucumber reached 900 and 450 mg kg^–1 in the dry weight, respectively. Excessively high Mn or/and Zn concentrations in the leaves reduced the fruit biomass production due to decreases in the number of fruits per plant, as well as the net assimilation rate, stomatal conductance, and transpiration rate, but increased the intercellular CO₂ levels. Initially, the Mn or Zn concentrations in the recirculating nutrient solution increased rapidly but gradually stabilized to maximal levels, while the corresponding concentrations in the leaves constantly increased until the end of the experiment. The uptake of Mg, Ca, Fe, and Cu was negatively affected, while that of K and P remained unaffected by the external Mn and Zn levels. The combination of high Mn and Zn seems to have no additive effects on the parameters investigated.     

铝和镉胁迫对两个大麦品种矿质营养和根系分泌物的影响

A hydroponic experiment was carried out to study the effect of aluminum （Al） and cadmium （Cd） on Al and mineral nutrient contents in plants and Al-induced organic acid exudation in two barley varieties with different Al tolerance. Al- sensitive cv. Shang 70-119 had significantly higher Al content and accumulation in plants than Al-tolerant cv. Gebeina, especially in roots, when subjected to low pH （4.0） and Al treatments （100 μmol L^-1 Al and 100 μmol L^-1 Al ＋1.0 μmol L^-1 Cd）. Cd addition increased Al content in plants exposed to Al stress. Both low pH and Al treatments caused marked reduction in Ca and Mg contents in all plant parts, P and K contents in the shoots and leaves, Fe, Zn and Mo contents in the leaves, Zn and B contents in the shoots, and Mn contents both in the roots and leaves. Moreover, changes in nutrient concentrations were greater in the plants exposed to both Al and Cd than in those exposed only to Al treatment. A dramatic enhancement of malate, citrate, and succinate was found in the plants exposed to 100 μmol L^-1 Al relative to the control, and the Al-tolerant cultivar had a considerable higher exudation of these organic acids than the Al-sensitive one, indicating that Al-induced enhancement of these organic acids is very likely to be associated with Al tolerance.     

Comparison of MnSO4 and MnEDTA for soybeans grown on two soils in the greenhouse

Abstract

A greenhouse experiment was conducted to compare MnSO₄ and MnEDTA as Mn sources. Four soil‐applied rates of each source were applied to two Coastal Plain soils, a Leefield s (pH 6.3) and an Alapaha is (pH 7.0). Plants were grown for 40 days and dry tissue weights were recorded along with leaf contents of Mn, Zn, Fe and Cu. The same ions were extracted from the soil with DTPA. The chelate source caused no differences in either extractable soil Mn or plant Mn between soils or among rates even when added at its highest rate of 2 μgMn/g. The sulfate source increased extractable soil Mn and plant Mn over the various rates but more so for the Alapaha soil than for the Leefield. Plant weights were not different between sources except on the averages for the Leefield soil. However, for the Leefield soil and the sulfate source, plant weights were lower for the check than for intermediate Mn rates due to Mn deficiency and lower for the high Ma rate (50 μg/g) presumably due to toxicity. A correlation coefficient of 0.866** was obtained for soil‐extracted Mn versus plant Mn concentration indicating that the DTPA was a good extractant for these two soils. High correlations between plant and soil Mn versus plant and soil Zn, Fe, and Cu for the chelate source showed that the MnEDTA affected metal ion availabilities other than just Mn. It was concluded that the MnSO₄ was the better source at the rates used and that for these soils the best rate was S μgMn/g applied to the soil.     

Effects of soil water content on growth,tillering, and manganese uptake of lowland rice grown in the water‐saving ground‐cover rice‐production system (GCRPS)

A 2‐year field experiment and a pot experiment were carried out to compare Mn uptake, tillering, and plant growth of lowland rice grown under different soil water conditions in the ground‐cover rice‐production system (GCRPS) in Beijing, North China. The field experiment was conducted in 2001 and 2002, including two treatments: lowland‐rice variety (Oryza sativa L. spp. japonica) grown under thin (14 μm) plastic‐film soil cover (GCRPS_plastic) at 80%–90% water‐holding capacity (WHC) and traditional lowland rice (paddy control) grown with 3 cm standing‐water table. The pot experiment was conducted in a greenhouse with four treatments: (1) traditional lowland rice: paddy control; (2) GCRPS, water‐saturated soil: GCRPS_saturated; (3) GCRPS at 90% water‐holding capacity (WHC): GCRPS_90%WHC; and (4) GCRPS at 70% WHC: GCRPS_70%WHC. Results of the field experiment showed that dry‐matter production, number of tillers, as well as N and Mn concentrations in rice shoots of GCRPS were significantly lower than in paddy control, while there was no significant difference in shoot Fe, Cu, Zn, and P concentration and nematode populations. In the pot experiment, shoot Mn concentration significantly decreased with decreasing soil water content, while soil redox potential increased. Shoot–dry matter production and tiller number of GCRPS_saturated were significantly higher than in other treatments. Significant correlations were observed between the shoot Mn concentration and tiller number at maximum tillering stage in the field and pot experiment, respectively. We therefore conclude that the limitation of Mn acquisition might contribute to the growth and yield reduction of lowland rice grown in GCRPS. The experiment provides evidence that GCRPS_plastic combined with nearly water‐saturated soil conditions helps saving water and achieving optimum crop development without visual or latent Mn deficiency as observed under more aerobic conditions.     

Effects of Nickel on Growth and Composition of Metal Micronutrients in Barley Plants Grown in Nutrient Solution

Abstract

A hydroponic experiment was conducted in a phytotron at pH 5.5 to study the effects of nickel (Ni) on the growth and composition of metal micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), of barley (Hordeum vulgare L. cv. Minorimugi). Four Ni treatments were conducted (0, 1.0, 10, and 100 μM) for 14 d. Plants grown in 100 μM Ni showed typical visual symptoms of Ni toxicity such as chlorosis, necrosis of leaves, and browning of the root system, while other plants were free from any symptoms. Dry weights were the highest in plants grown in 1.0 μM Ni, with a corresponding increase in the chlorophyll index of the plants, suggesting that 1.0～10 μM Ni needs to be added to the nutrient solution for optimum growth of barley plants. The increase of Ni in the nutrient solutions increased the concentrations of Cu and Fe in roots, while a decrease was observed in shoots. The concentrations of Mn and Zn in shoots and roots of plants decreased with increasing Ni supply in the nutrient solution. Shoot concentrations of Cu, Fe, Mn, and Zn in plants grown at 100 μ M Ni were below the critical levels for deficiency. Plants grown at 1.0 μ M Ni accumulated higher amounts of Cu, Fe, Mn and Zn, indicating that nutrient accumulation in plants was more influenced by dry weights than by nutrient concentrations. The translocation of Cu and Fe from roots to shoots was repressed, while that of Mn and Zn was not repressed with increasing Ni concentration in the nutrient solution.     

Effects of lime,phosphorus, manganese,copper, and zinc on plant mineral composition,yield of itarley,and level of extractable nutrients for an acid Swedish mineral soil

Abstract

A pot experiment was performed during the 1992 growing season on an acid, sandy topsoil taken from a Swedish liming experiment. A central composite experimental design was used in order to study the effects of supply of phosphorus (P) and micronutrients at different liming levels on yield of barley (Hordeum vulgare L. c.v. Golf), mineral content in plant, straw, and grain, and level of soil extractable nutrients. The results showed no increase of yield due to liming despite the fact that lime increased the yield significantly in the field experiment. The soil appeared initially to have a good balance between the nutrients included in the experimental design with the exception of P. An excessive supply of manganese (Mn) decreased the yield. The contents of calcium (Ca) and aluminum (Al) in the plant were hardly affected by the treatments, while the contents of P, Mn, copper (Cu), and zinc (Zn) more than doubled compared to no supply. The contents of P, Cu, and Zn were mainly influenced by the supply of the actual element, while the content of Mn was more closely related to the supply of lime. Soil pH(H₂0) and CaCl₂‐extractable P, Mn, Cu, and Zn were highly related to the supplies of lime, P, Mn, Cu and Zn, respectively. Only a few interactions were observed.     

The effect of paclobutrazol on mineral nutrition of apple seedlings 1

Greenhouse grown ‘Golden Delicious’ apple seedlings were treated with soil drenches of paclobutrazol (PP333) at rates equivalent to 0.1, 0.2, 0.4, 0.8, and 1.6 kg of active ingredient (a.i.) ha.^‐1 Eleven weeks after treatment initiation, seedlings were harvested, divided into leaves, stems, and roots, weighed and analyzed for the content of macro‐and microelements. Shoot growth rate, leaf area, and total dry weight showed a decreasing trend with increasing rates of PP333. In contrast, specific leaf weight increased in response to growth regulator treatments. The total amount of N, Zn, and Cu absorbed by seedlings was not affected and that of K, Ca, Mg, and Mn was decreased by PP333 treatments. Concentration of Ca and Mn in leaves, N in roots, and N, Ca, Mg, Mn, Zn, and Cu in stems increased in response to PP333 treatments. The magnitude of these increases were dependent on the rate of growth regulator applied. Potassium was the only element which declined in concentration in leaves and stems; this was true, however, only at the two highest rates of PP333 (0.8 and 1.6 kg ha^‐1) Root K concentration was not affected by PP333 treatments.     

外源NO对铜胁迫下番茄光合、生物发光特性及矿质元素吸收的影响

采用营养液培养,研究了外源一氧化氮（NO）供体硝普钠(Sodium nitroprusside, SNP)对50 μmol/L铜（Cu）胁迫下番茄叶片叶绿素含量、光合特性、生物发光强度和矿质营养元素的影响。结果表明,在Cu胁迫下,外施100 μmol/L SNP显著提高番茄叶片叶绿素a、叶绿素b、叶绿素a+b含量、叶绿素a/b比值、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和叶片中Cu、Ca、Fe、Zn、Mn以及根系中Cu、K、Fe、Zn的含量; 显著降低叶片超微弱发光强度、荧光强度、磷光强度、胞间CO2浓度(Ci)和根系中Ca的含量。然而,SNP对Cu胁迫下的缓解效应可被NO的清除剂血红蛋白所抑制。在Cu处理液中加入100 μmol/L NO-x（NO的分解产物）或100 μmol/L亚铁氰化钠（SNP的相似物或分解产物）,与Cu胁迫处理差异不显著。表明外源NO可以通过改善Cu胁迫下番茄叶片光合特性,降低超微弱发光、荧光、磷光强度,维持矿质营养元素平衡,缓解Cu胁迫对番茄的抑制作用。     

铁和不同形态氮素对玉米植株吸收矿质元素及其在体内分布的影响 Ⅱ.对铁、锰、铜、锌等营养元素的影响

用营养液培养方法研究了铁和两种形态氮素对玉米植株吸收铁、锰、铜、锌等微量元素及其在体内分布的影响。结果表明:与硝态氮(NO₃^--N)相比,铵态氮(NH₄⁺-N)显著提高了玉米对铁的吸收,降低了对锰、铜及锌的吸收。供铁也明显提高了植株地上部铁的吸收总量,降低了锰及锌的吸收量,尤其是在供应No₃^--N时这种作用更为明显。在缺铁条件下,NH₄⁺-N处理的玉米新叶中铁的含量明显高于NO₃^--N处理;而新叶、老叶、茎中锰、锌、铜含量以及根中锰、锌含量都明显低于NO₃^--N处理。但使用NH₄⁺-N时,根中铜的含量较高。在供铁条件下,NH₄⁺-N处理的玉米植株四个不同器官中锰和锌的含量显著低于NO₃^--N处理的植株,而铜的含量正好相反。在缺铁条件下,玉米新叶中活性锰、活性锌的含量显著高于供铁处理;与NO₃^--N相比,NH₄⁺-N的供应也显著降低了玉米新叶中活性锰以及活性锌的含量。     

曼地亚红豆杉(Taxus media cv“Hicksii”)栽培基质中适宜的锰、锌、铜浓度及采收时期研究

【目的】紫杉醇具有独特的抗癌机理和广谱强效的抗癌活性,被认证为目前最有效的天然抗癌药物之一。曼地亚红豆杉作为提取紫杉醇重要地天然源料,而备受重视。本试验旨在分析锰(Mn)、锌(Zn)和铜(Cu)三种微量元素对两种树龄曼地亚红豆杉植株生长及紫杉醇含量的影响,为曼地亚红豆杉药用原料林定向培育及通过合理施用微肥确定适宜采收期提供科学借鉴。【方法】以3年和5年生曼地亚红豆杉"Hicksii"幼苗为材料,采用砂基培养方式,使用高效液相色谱检测了施用不同浓度锰(0、4.50、9.00、13.50和18.00μmol/L)、锌(0、0.15、0.30、0.45和0.60μmol/L)和铜(0、0.40、0.80、1.20和1.60μmol/L)对3年和5年生曼地亚红豆杉"Hicksii"树苗生长及紫杉醇含量的影响。【结果】1)3种微量元素对两种不同年龄树苗的生长和枝叶紫杉醇含量影响显著。最适宜3年和5年生树苗生长(株高、地径、新梢长度)和生物量(枝叶与根系鲜/干重)积累的Mn浓度为9.00μmol/L,Zn浓度为0.40μmol/L;3年生树苗的最适宜Cu浓度为0.30μmol/L,5年生为0.15μmol/L。3年生树苗的Mn浓度为9.00μmol/L,5年生树苗为4.50μmol/L以及两种树龄树苗的Zn浓度为0.40μmol/L和Cu浓度为0.30μmol/L时,微量元素有利于两种不同年龄树苗枝叶的紫杉醇积累。高于该适宜浓度则抑制树苗枝叶的紫杉醇积累,且浓度越高抑制作用越强。2)3种微量元素处理下,5年生树苗紫杉醇含量显著高于3年生树苗,对两种树苗紫杉醇含量影响效果顺序为MnZnCu。3)在生长期3~10月,不同浓度Mn、Zn、Cu处理下的两种树苗均表现出相同规律:3~6月树苗紫杉醇积累量逐渐降低,6月降到最低,7月开始逐渐升高,9~10月含量趋于稳定。【结论】施用微量元素Mn 9.00μmol/L、Zn 0.40μmol/L和Cu 0.15~0.30μmol/L,5年龄"Hicksii"树苗,在9~10月份进行采收是紫杉醇含量高的关键点。     

Effects of zinc fungicides and different zinc fertilizer application methods on soluble and total zinc in potato plant shoots

Abstract

The experiment was carried out to evaluate the effects of fungicides [with or without zinc (Zn)] and different Zn fertilizer application methods (no fertilizer; soil application; shoot application; soil plus shoot application) on the soluble and total Zn in the dry matter of potato shoots. Zinc fertilizer was applied to the shoots at 20 and 45 days after plant emergence (DAE), immediately before plant sampling. At 25 DAE, Zn fungicide increased soluble and total Zn in the fourth leaf. The same occurred, at 45 DAE, with the Zn fertilizer applied to the shoots. It were not observed significant increases on both soluble and total Zn contents in the fourth leaf of plants that received soil Zn fertilization. Even in the leaves with 262 mg Zn kg^‐1, there was no phytotoxicity symptoms. The total Zn concentration at 20 DAE was the best index correlated to potato tuber yield reaching 50.9 mg Zn kg^‐1 in the fourth leaf of plants at the highest marketable tuber yield treatment. Plant nutrient element contents [phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), and manganese (Mn)] were not affected by the treatments.     

Effects of excess manganese on mineral uptake in mycorrhizal sorghum

Associations between vesicular‐arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non‐mycorrhizal (‐VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143–2 (UT1 43) and Gl. etunicatum UT316A‐2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 μM of added Mn (as manganese chloride) above the basal solution (18 μM). Shoot and root dry matter followed the sequence of UT316 > UT143 > ‐VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than ‐VAM plants, although ‐VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.     

Varied rates of mycorrhizal inoculum on growth and nutrient acquisition by barley grown with drought stress

Effectiveness of arbuscular mycorrhizal fungi (AMF) is crucial for maximum plant growth and acquisition of mineral nutrients under drought. The objective of this research was to determine effects of varied rates of AMF inoculum on plant growth and acquisition of phosphorus (P), zinc (Zn), copper (Cu), and manganese (Mn) by barley (Hordeum vulgare L. cv. SLB‐6) grown with and without drought stress (WS and nonWS). Plants inoculated with four inoculum rates [control (M₀), 120 (M₁), 240 (M₂), and360 (M₃) spores per 100 g dry soil] of Glomus mosseae were grown in a low P silty clay (Typic Xerochrept) soil (pH=8.0) mix in a greenhouse for 45 days. Root AMF colonization increased as inoculum rate increased in plants grown with WS and nonWS. Leaf area and shoot and root dry matter (DM) increased as inoculum rate increased up to M₂ regardless of soil moisture. Shoot concentrations of P, Cu, and Mn were generally higher for mycorrhizal (AMF) than for nonmycorrhizal (nonAMF) plants grown with both WS and nonWS. Shoot contents of P, Zn, Cu, and Mn were higher for AMF than for nonAMF plants grown with nonWS, and shoot contents of P were higher for AMF than for nonAMF plants with WS. For plants grown with WS and nonWS, contents of P, Zn, Cu, and Mn were generally higher for plants inoculated with M₂ compared to other rates of inoculum. The results of this study indicated that plant responses to root colonization with AMF were dependent on AMF rate and soil moisture. Based on enhancements in plant DM and mineral acquisition traits, M₂ inoculum was the most effective rate of inoculation for this AMF isolate.     

Deficiency of manganese is alleviated more by low zinc than low copper in wheat

Abstract

Wheat (Triticum aestivum L.) var. Sonalika was grown in purified sand in complete nutrient solution (normal), deficient manganese (Mn) (0.0055 mg L^‐1), deficient copper (Cu) (0.0065 mg L^‐1), deficient zinc (Zn) (0.0065 mg L^‐1), deficient ?n/deficient Cu, deficient ?n/deficient Zn, deficient Cu/deficient Zn, and deficient ?n/deficient Cu/deficient Zn treatments. The deficiency of Mn decreased the biomass, concentration of Mn, chlorophyll, sugars, Hill reaction activity, acid phosphatase activity, and increased that of peroxidase and polyphenol oxidase. The magnitude of Mn deficiency effects was mitigated to variable extent when Mn was deficient along with deficient Cu and/or deficient Zn. The effects of either Cu or Zn deficiency viz., intensification of foliar symptoms, decrease in biomass, leaf Cu/Zn, seed yield and starch content were increased further in combined deficiency of Cu and Zn. The stimulation in acid phosphatase and decrease in the activity of polyphenol oxidase and carbonic anhydrase in Cu or Zn deficient leaves were further aggravated when both Cu and Zn were deficient together. All these changes reveal a synergism between Cu and Zn in wheat.     

Phytosiderophore release from manganese‐induced iron deficiency in barley

An experiment was conducted in the phytotron with barley (Hordeum vulgare L. cv. Minorimugi) grown in nutrient solution to compare iron (Fe) deficiency caused by the lack of Fe with manganese (Mn)‐induced Fe deficiency. Dark brown spots on older leaves and stems, and interveinal chlorosis on younger leaves were common symptoms of plants grown in either Mn‐toxic or Fe‐deficient treatments. Dry matter yield was affected similarly by Fe deficiency and Mn toxicity. The Mn toxicity significantly decreased the translocation of Fe from roots to shoots, caused root browning, and inhibited Fe absorption. The rate of Fe translocated from roots to shoots in the 25.0 μM Mn (toxic) treatment was similar to the Fe‐deficient treatment. Manganese toxicity, based on the release of phytosiderophore (PS) from roots, decreased from 25.0>250>2.50 uM Mn. The highest release of PS from roots occurred 7 and 14 days after transplanting (DAT) to Mn‐toxic and Fe‐deficient treatments, respectively; but was always higher in the Fe‐deficient treatment than the Mn‐toxic treatments. The release of PS from roots decreased gradually with plant age and with severity of the Mn toxicity symptoms. The PS content in roots followed the PS release pattern.     

Some interactions of cadmium with other elements in plants

Abstract

Cadmium in solution culture at 10^‐4 M decreased Mn concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) at both low and high concentrations of Mn (noncompetitive inhibition). When Mn was decreased, the concentrations of Fe and several other ions were simultaneously increased, particularly in leaves and roots. Toxicity due to the 10^‐6 M Cd and the 10^‐4 M Mn was additive in the experiment. When barley (Hordeum vulgare L. Atlas57)was grown in amended soil, 15μg Fe as DTPA (diethylene triamine pentaacetic acid) per g soil resulted in increased uptake of Cd and in somewhat greater yield depression for soil pH of 3.9, 6. 0, and 7.6. Acidification of soil without DTPA also increased Cd uptake to high levels with associated yield decrease. The Cd decreased the uptake of Mn and Cu most when CaCO₃ had also been added to the soil. When salts were added to soil with Cd before bush beans were grown, KCl (200 μg K/g soil), and equivalent KH₂PO₄ increased Cd concentrations of leaves while CaSO₄ and KCl did so for roots. In bush beans with different levels of Cd and Zn, there were no yield interactions, but some interactions of Cd on Zn concentrations in leaves, stems, and roots at the high Zn level.     

Tolerance of rice plants to trace metals

Abstract

The tolerance of rice (Oryza sativa L. C.V. Earlirose) to various trace metal excesses was tested to determine if high levels of the trace metals found in some field‐grown plants were at toxicity levels. In one experiment, levels of 2200 μg Zn/g dry weight, 44 μg Cu/g dry weight, 4400 μg Mn/g dry weight, and 32 μg Pb/g dry weight in shoots of young plants had no adverse effects on vegetative yields. A level of 3160μgZn/ g dry weight decreased yields about 40% (P = . 05). In another test 51 μg Cu/g dry weight or 94 μg Pb/g dry weight did not decrease vegetative yields. Boron supplied at 10^‐3 MH₃BO₃ not only caused no toxicity but resulted in only 144 μg B/g dry weight in shoots. Root levels of Zn were about equal to those in shoots; Mn levels were lower in roots than in shoots (1/4 to 1/10); B levels were generally low in both shoots and roots with roots 1/10 that of shoots; Cu levels were higher in roots than in shoots. Rice was tolerant of a high level of Cr. The tolerance of rice to high levels of some trace metals in these experiments may be related to high P levels in plants.     

IS CHLOROPHYLL FLUORESCENCE TECHNIQUE A USEFUL TOOL TO ASSESS MANGANESE DEFICIENCY AND TOXICITY STRESS IN OLIVE PLANTS?

A 130-day hydroponic experiment was carried out in a glasshouse to examine whether manganese (Mn) concentration in the nutrient solution affects the nutritional status of olive plants and to find out whether the chlorophyll fluorescence technique is suitable to assess Mn toxicity and/or deficiency stress in olive plants prior to the appearance of these two nutritional disorders. For this purpose, chlorophyll fluorescence parameters (F_v/F_m and F_v/F₀ ratios) were recorded every 40 days in the leaves of ‘Kothreiki’ and ‘FS-17’ olive cultivars, which were irrigated with Hoagland's nutrient solutions containing various Mn concentrations. In parallel the elongation of the main shoot of all experimental plants, as well as the concentrations of Mn, iron (Fe), zinc (Zn), boron (B), phosphorus (P), calcium (Ca), magnesium (Mg), and potassium (K) in their leaves were recorded. The following Mn treatments were applied: 0 μM Mn (to induce Mn deficiency), 40 μM Mn (to promote normal growth), and 640 μM Mn (to induce Mn toxicity). Our results indicated that not only the rate of shoot elongation but also the fluctuation with time of the leaf concentrations of all determined mineral elements (except for Mn) was not significantly affected by the Mn concentration in the nutrient solution, irrespectively of the cultivar. This was not observed with regard to the time variation of the F_v/F_m and F_v/F₀ ratios, where the values of these parameters were significantly reduced in the 640 μM Mn treatment at the 80th and 130th day of the experiment in both olive cultivars, compared to the relevant previous ones (those of the days 0 and 40th), something which did not happen in the other two Mn treatments (0 and 40 μM). However, in none of the two cultivars tested and in any of the three Mn treatments (0, 40 and 640μM) the F_v/F_m and F_v/F₀ ratios did not drop below the critical values of 0.8 and 4, respectively, even at the end of the experiment, where high Mn concentrations were found in the leaves of both cultivars treated with 640 μM Mn (616 μg g^?1 d.w. in ‘FS-17’ and 734 μg g^?1 d.w. in ‘Kothreiki’). Symptoms of Mn toxicity (curling and brown speckles) were observed in the top leaves of both cultivars, after the 90th day of the experiment. At the same time, the final leaf Mn concentrations (those of the 130th day of the experiment) in plants grown under 0 μM Mn were 23 μg g^?1 d.w. in ‘FS-17’ and 20 μg g^?1 d.w. in ‘Kothreiki’, i.e., a little above of the deficiency range (<20 μg g^?1 d.w.). At the 130th day, Mn concentration in nutrient solution, as well as Mn concentration in the leaves of both olive cultivars was negatively correlated with the leaf concentration of Fe and the values of the F_v/F_m and F_v/F₀ ratios, and positively with the concentrations of Zn and P in the leaves. Finally, the periodical measurement of the F_v/F_m and F_v/F₀ ratios was proved to be a non-reliable means to predict the appearance of the visible symptoms of Mn toxicity in olive leaves (although their values declined significantly at the 80th and 130th day of the experiment in both olive cultivars).     

Effects of excess aluminum on mineral uptake in mycorrhizal sorghum

Soil acidity is often associated with toxic aluminum (Al), and mineral uptake usually decreases in plants grown with excess Al. This study was conducted to evaluate the effects of Al (0, 35, 70, and 105 μM) on Al, phsophorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn,) and copper (Cu) uptake in shoots and roots of sorghum [Sorghum bicolor (L.) Moench, cv. SC283] colonized with the vesicular‐arbuscular mycorrhizal (VAM) fungi isolates Glomus intraradices UT143–2 (UT143) and Glomus etunicatum UT316A‐2 (UT316) and grown in sand (pH 4.8). Mycorrhizal (+VAM) plants had higher shoot and root dry matter (DM) than nonmycorrhizal (‐VAM) plants. The VAM treatment had significant effects on shoot concentrations of P, K, Ca, Fe, Mn, and Zn; shoot contents of P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu; root concentrations of P, S, K, Ca, Mn, Zn, and Cu; and root contents of Al, P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu. The VAM effects on nutrient concentrations and contents and DM generally followed the sequence of UT316 > UT143 > ‐VAM. The VAM isolate UT143 particularly enhanced Zn uptake, and both VAM isolates enhanced uptake of P and Cu in shoots and roots, and various other nutrients in shoots or roots.