Towards soil management with Zn and Mn: estimates of fertilisation efficacy of Citrus trees

Nutrient management recommendations for fruit crops lack the understanding of the efficiency of soil fertilisation with manganese (Mn) and zinc (Zn), which could substitute, in part, the traditional foliar applications. Fruit yield of trees in response to Zn and Mn supply via soil may be limited either by sorption reactions with soil colloids or low solubility of fertilisers. We investigated the effects of fertiliser sources and rates of Mn and Zn applied to soils with different sorption capacities on nutrient uptake, biochemical responses and biomass of Citrus. Two experiments were carried out with 2‐year‐old sweet orange trees that received applications of Mn or Zn. The first experiment evaluated the application of Mn fertilisers (MnCO₃ and MnSO₄) at three levels of the nutrient (0, 0.7 and 3.5 g plant^?1 of Mn) in two types of soil (18.1% and 64.4% of clay, referred to as sandy loam and clay soils, respectively). The second experiment, likewise, evaluated Zn fertilisers (ZnO and ZnSO₄) and nutrient levels (0, 1.0 and 5.0 g plant^?1 of Zn). Application of Mn and Zn increased nutrient availability in the soils as well as leaf nutrient concentrations in the trees. The lowest rates, 0.7 g plant^?1 of Mn and 1.0 g plant^?1 of Zn, both as sulphate, were sufficient to supply these micronutrients to sufficient levels in leaves, flowers and fruits. Metal toxicity to plants occurred with higher doses of both nutrients and to a large extent in the sandy soil. In this case, protein bands lower than 25 kDa were observed as well a decrease on leaf chlorophyll content. In the clay soil, despite increased micronutrient concentrations in the plant, responses were less pronounced because of higher adsorption of metals in the soil. Superoxide dismutase (SOD, EC 1.15.1.1) isoenzyme activity was determined by non‐denaturing polyacrylamide gel electrophoresis (PAGE). The Cu/Zn‐SOD isoenzymes increased with increased Zn rates, but in contrast, when Mn was applied at the highest rate, the activity of Cu/Zn‐SODs decreased. The SOD activity pattern observed indicated increased production of superoxide and consequently an oxidative stress condition at the highest rates of Zn and Mn applied. The results demonstrated that the soil application of Mn and Zn can supply nutrient demands of orange trees, however the low solubility of fertilisers and the high sorption capacity of soils limit fertilisation efficiency. On the contrary, application of sulphate source in sandy soils may cause excess uptake of Mn and Zn and oxidative stress, which impairs the photosynthetic apparatus and consequently tree growth.     

Manganese application alleviates the water deficit-induced decline of N2 fixation

Water deficit is a very serious constraint on N₂ fixation rates and grain yield of soybean (Glycine max Merr.). Ureides are transported from the nodules and they accumulate in the leaves during soil drying. This accumulation appears responsible for a feedback mechanism on nitrogen fixation, and it is hypothesized to result from a decreased ureide degradation in the leaf. One enzyme involved in the ureide degradation, allantoate amidohydrolase, is manganese (Mn) dependent. As Mn deficiency can occur in soils where soybean is grown, this deficiency may aggravate soybean sensitivity to water deficit. In situ ureide breakdown was measured by incubating soybean leaves in a 5 mol m ^{? 3} allantoic acid solution for 9 h before sampling leaf discs in which remnant ureide was measured over time. In situ ureide breakdown was dramatically decreased in leaves from plants grown without Mn. At the plant level, allantoic acid application in the nutrient solution of hydroponically grown soybean resulted in a higher accumulation of ureide in leaves and lower acetylene reduction activity (ARA) by plants grown with 0 mol m ^{? 3} Mn than those grown with 6·6 mol m ^{? 3} Mn. Those plants grown with 6·6 mol m ^{? 3} Mn in comparison with those grown with 52·8 mol m ^{? 3} Mn had, in turn, higher accumulated ureide and lower ARA. To determine if Mn level also influenced N₂ fixation sensitivity to water deficit, a dry‐down experiment was carried out by slowly dehydrating plants that were grown in soil under four different Mn nutritions. Plants receiving no Mn had the lowest leaf Mn concentration, 11·9 mg kg ^{? 1}, and had N₂ fixation more sensitive to water deficit than plants treated with Mn in which leaf Mn concentration was in the range of 21–33 mg kg ^{? 1}. The highest Mn treatments increased leaf Mn concentration to 37·5 mg kg ^{? 1} and above but did not delay the decline of ARA with soil drying, although these plants showed a significant increase in ARA under well‐watered conditions.     

Effects of phosphorus and iron fertilizers on the growth of two soybean varieties at two soil temperatures

The influence of FeEDDHA (0, 0.2 and 2 μg Fe g⁻¹ soil) and NaH₂PO₄·H₂O (0 and 120 μg Pg⁻¹ soil) on the growth of two Fe-ineffective soybean (Glycine max L. Merr.) varieties (anoka and T203) on a calcareous soil at two soil temperatures (16 and 24°C) was compared under greenhouse conditions. The two soybean varieties differed in the following respects: (a) T203 accumulated smaller concentrations of Fe in washed tops than Anoka under comparable conditions; (b) T203 was more susceptible to Fe deficiency and its accentuation by high levels of fertilizer P than Anoka; (c) T203 accumulated lower quantities of Mn in tops than Anoka under comparable conditions; (d) T203, but not Anoka, developed Mn deficiency symptoms when treated with P and 2 μg Fe g⁻¹ at 16°C. Fe deficiency was more severe in both varieties at the higher soil temperature due apparently to: (a) greater plant concentration of P in tops at 24°C; and/or (b) an increased rate of plant growth and greater dilution of Fe in young tissue at 24°C. Foliar P concentration was increased much more than foliar Fe concentration by an increase in soil temperature. Severely Fe deficient T203 plants grown without FeEDDHA at 24°C accumulated less foliar Mn than their FeEDDHA counterparts. Comparisons of Fe effectiveness of various soybean cultivars based on relative responses to FeEDDHA can be influenced by differential effects on Mn nutrition.     

Plant regeneration from shoot apical meristems of Melia azedarach L. (Meliaceae)

A protocol was developed for plant regeneration of Melia azedarach L. by in vitro culture of apical meristem (0.5 mm in length). The influence of six clones was investigated. The culture procedure comprised two sequential steps: 1) Induction of shoots by in vitro culture of axillary buds from adult trees (10–15 years old) by culture on Murashige and Skoog (1962) medium (MS) supplemented with 0.5 mg·dm⁻³ BAP (6-benzylaminopurine), 0.1 mg·dm⁻³ IBA (indolebutyric acid), and 0.1 mg·dm⁻³ GA₃ (gibberellic acid). The Multiplication of the regenerated shoots was achieved in MS + 0.5 mg·dm⁻³ BAP + 0.1 mg·dm⁻³ GA₃. 2) In vitro culture of the apical meristems from the regenerated shoots in MS medium (0.7 %) supplemented with various combinations of BAP and IBA. Maximum shoot proliferation was obtained on MS medium supplemented with 0.5 mg·dm⁻³ BAP and 0.1 mg·dm⁻³ IBA. Regenerated shoots were rooted on MS + 3.5 mg·dm⁻³ IBA (4 days) followed by subculture on MS lacking growth regulators (30 days). Complete plants were transferred to soil.     

Development and evaluation of Trichoderma asperellum preparation for control of sheath blight of rice (Oryza sativa L.)

Sheath blight, which is caused by Rhizoctonia solani, is a disease that majorly impacts rice production. A biocontrol agent used for control rice sheath blight must be sprayed on the stem at specific times during rice growth, a process that is labour-intensive and renders the antagonist vulnerable to environmental factors. In this study, Trichoderma asperellum T12 was used to produce preparation by solid-state fermentation using a surface-response method. Rice hull was selected as a carrier based on its ability to sustain the T12 floating in the water and protect T12 from ultraviolet irradiation. The production of a T12-based preparation required 32% wheat bran, 7% inoculum, 2.3 g kg^?1 (NH₄)₂SO₄ and 65% water content, with fermentation at 27.5°C for 30 days and agitation every six days. The preparation demonstrated 90% biocontrol efficacy and significantly (P > 0.05) increased the seed-set rate and 1000-grain weight as compared with the pathogen treatment. The population of Trichoderma on the surface of rice leaf sheath in the treatment applied with T12 preparation increased from 232 cfu (colony forming units) g^?1 fw (fresh weight) to 436 cfu g^?1 fw during rice growth stage, which was significantly (P > 0.05) higher than pathogen treatment. The population of R. solani on the leaf sheath increased from 41 cfu g^?1 fw to 271 cfu g^?1 fw in the pathogen treatment, while remained stable (P > 0.05) at level of 10–23 cfu g^?1 fw in T12 preparation applied treatment. Biocontrol of sheath blight by the addition of the preparation to the soil is effective and decreases the costs of agro-industrial waste disposal.     

Endophytic fungus Piriformospora indica induced systemic resistance against rice sheath blight via affecting hydrogen peroxide and antioxidants

In this study, the effect of endophytic fungus Piriformospora indica on Rhizoctonia solani AG1-IA, causal agent of sheath blight disease, was investigated. In addition, plant defence responses activated in P. indica-inoculated rice plants were analysed. Two-week-old seedlings were inoculated by dipping their roots in P. indica chlamydospore suspension and transferred to pots containing sterilized soil. After two weeks, the seedlings pre-inoculated with P. indica were inoculated with R. solani. Statistical analysis of biological indicators showed that application of P. indica increased both fresh and dry weight of rice shoots and roots, compared to those of uninoculated healthy controls and the samples only inoculated with R. solani. Accumulation of hydrogen peroxide (H₂O₂) and activity of antioxidants such as superoxide dismutase (SOD) and guaiacol peroxidase (GPX) in plants inoculated with P. indica, R. solani, and P. indica-R. solani were investigated. The obtained results revealed that P. indica not only increased the plant biomass, but also delayed the infection process of R. solani and decreased sheath blight severity. Decreased severity of the disease was associated with decreased levels of H₂O₂ and increased SOD activity. Considering the necessity of reducing fungicide application, using P. indica in seedling bed before transplantation to the field could be a novel and effective method to increase rice production and decrease sheath blight progress.     

Baseline sensitivity and efficacy of thifluzamide in Rhizoctonia solani

Thifluzamide is a SDHI (succinate dehydrogenase inhibitor) fungicide, which interferes with succinate ubiquinone reductase in the mitochondrial electron transport chain of fungi. Presently, jinggangmycin is the major fungicide extensively used for the control of rice sheath blight caused by Rhizoctonia solani and resistance to jinggangmycin was first reported to occur in China. A total of 128 isolates of R. solani from Anhui Province of China were characterised for the baseline sensitivity to thifluzamide. The isolates were very sensitive to thifluzamide and the baseline sensitivity curve was unimodal with an average EC₅₀ value of 0.058 ± 0.012 µg mL^?1. However, EC₅₀ values of boscalid (another SDHI fungicide) for inhibition of mycelial growth of 22 arbitrarily selected R. solani isolates ranged from 1.89 to 2.68 µg mL^?1. Thifluzamide applied at 110 µg mL^?1 exhibited excellent protective and curative activity against rice sheath blight and provided 81.1–91.0% protective or curative control efficacy. In field trials in 2010 and 2011, control efficacies of thifluzamide at 82 g.a.i ha^?1 15 and 30 days after second application were 84.2% and 86.7%, respectively, suggesting excellent activity against sheath blight. There was a statistically significant difference in the efficacy between thifluzamide and boscalid or jinggangmycin. These results suggested that thifluzamide should be a good alternative fungicide to jinggangmycin for the control of rice sheath blight.     

Arbuscular Mycorrhizal Fungi Enhance Zinc and Nickel Uptake from Contaminated Soil by Soybean and Lentil

Generally, soils in Pakistan are deficient in P and N. Due to intensive cropping and irrigation, Pakistani soils have also become deficient in micronutrients such as Zn, Fe, Cu, and Mn. Arbuscular mycorrhizal fungi, which form symbiotic associations with roots of most land plants, are known to enhance uptake of P and trace elements such as Cu, Ni, Pb, and Zn. The present study was conducted to investigate the role of arbuscular mycorrhizae (AM) in uptake of nickel (Ni) and zinc (Zn) by crops viz. soybean (Glycine max (L.) Merrill) and lentil (Lens culinaris Medic). Zn and Ni were applied as ZnSO₄ 7H₂O and NiCl₂ respectively, in four concentrations (0.0, 1.0, 3.0, and 5.0 g kg^-1 soil). AM inoculum consisted of sand containing sporocarps, spores, and AMF infected root pieces from a pot culture of Glomus mosseae. Control plants received pot culture filtrate containing soil microflora minus AM fungal propagules. A significant difference (p < 0.05) was observed in the dry weights of roots and shoots of the mycorrhizal (M) and nonmycorrhizal (NM) cereal plants. The sievate-amended treatments did not stimulate plant growth to the same extent as the AM fungal amended treatments. Trace metals inhibited the extent of mycorrhizal colonization of the cereal roots. The concentrations of the trace metals in the plant tissues of 12-week old cereal plants were found significantly (p < 0.05) higher in M than NM plants. These results indicate that mycorrhize can be used as effective tools to supply sufficient Zn in generally Zn-deficient Pakistani soils and to ameliorate the toxicity of trace metals in polluted soils. The contents of Ni in mycorrhizal soybean plant tissues were higher than those in the mycorrhizal lentil plant tissues. The implications of these results in mycorrhizo remediation of agricultural soils are discussed.     

m-Hydroxyphenylacetic and m-Methoxyphenylacetic Acids of Rhizoctonia solani: Their Effect on Specific Root-Nodule Activity and Histopathology in Soybean

m-Methoxyphenylacetic acid (m-OMePAA), a derivative of m-hydroxyphenylacetic acid (m-OHPAA), having the same chemical composition as that phytotoxic compound produced in culture by Rhizoctonia solani, a fungal pathogen of soybean, reduced growth and symbiotic N₂-fixation activity of ‘Tracy’ soybeans in soil: perlite at 1.5 × 10^-4 M, the lowest concentration used. At twice this concentration m-OMePAA was strongly teratogenic and caused root hypertrophy and root fasciation. At 1.2 × 10^-3 M, m-OMePAA nearly suppressed seed germination. m-OMePAA at the minimum concentration used and equivalent concentrations of the culture filtrate fraction (m-OHPAA and m-OMePAA) caused cytopathological and histopathological disturbances in the nodule central tissue, extrusion of the nucleoli, and abnormal nuclci. The data indicate that these phytotoxic compounds of R. solani are involved in nodule impairment and reduced N₂-fixation in soybean.     

Growth,net photosynthesis and leaf nutrient status of <Emphasis Type="Italic">Fagus crenata</Emphasis> seedlings grown in brown forest soil acidified with H<Subscript>2</Subscript>SO<Subscript>4</Subscript> or HNO<Subscript>3</Subscript> solution

To obtain basic information for evaluating critical loads of acid deposition for protecting Japanese beech forests, growth, net photosynthesis and leaf nutrient status of Fagus crenata seedlings grown for two growing seasons in brown forest soil acidified with H₂SO₄ or HNO₃ solution were investigated. The whole-plant dry mass of the seedlings grown in the soil acidified by the addition of H₂SO₄ or HNO₃ solution was significantly less than that of the seedlings grown in the control soil not supplemented with H⁺ as H₂SO₄ or HNO₃ solution. However, the degrees of reduction in the whole-plant dry mass and net photosynthetic rate of the seedlings grown in the soil acidified by the addition of H⁺ as H₂SO₄ solution at 100 mg l^–1 on the basis of air-dried soil volume (S-100 treatment) were greater than those of the seedlings grown in the soil acidified by the addition of H⁺ as HNO₃ solution at 100 mg l^–1 (N-100 treatment). The concentrations of Al and Mn in the leaves of the seedlings grown in the S-100 treatment were significantly higher than those in the N-100 treatment. A positive correlation was obtained between the molar ratio of (Ca+Mg+K)/(Al+Mn) in the soil solution and the relative whole-plant dry mass of the seedlings grown in the acidified soils to that of the seedlings grown in the control soil. Based on the results, we concluded that the negative effects of soil acidification due to sulfate deposition are greater than those of soil acidification due to nitrate deposition on growth, net photosynthesis and leaf nutrient status of F. crenata, and that the molar ratio of (Ca+Mg+K)/(Al+Mn) in soil solution is a suitable soil parameter for evaluating critical loads of acid deposition in efforts to protect F. crenata forests in Japan.     

Growth and Protein Content in Colletotrichum circinans, Fusarium solani and Rhizoctonia solani in Liquid Culture

The phytopathogenic fungi Colletotrichum circinans, Fusarium solani, and Rhizoctonia solani were incubated in aerated (0, 0.5, 1 dm³ min^–1) potato dextrose broth (PDB) or Czapek-Dox broth (CDB), under 0-, 12- or 24-h photoperiods. Greater dry mass was produced in PDB. Higher air flows improved dry mass of F. solani and R. solani. The 24-h photoperiod improved F. solani dry mass. Except for F. solani, which was not affected, incubation in PDB increased protein content. The no air treatment increased protein content in F. solani, 0.5 dm³ min^–1 produced the highest protein content in R. solani, but air flow-rate did not affect C. circinans. Incubation in the dark produced the lowest protein content in C. circinans, the highest under the 24-h photoperiod for R. solani, and photoperiod did not affect protein content in F. solani. Protein content in R. solani, incubated in CDB, was lowest at the 0 dm³ min^–1 air flow at all photoperiods. Molecular masses of most proteins were under 30 kDa, and numbers of bands in SDS-PAGE gels varied with air flow. In CDB, especially under 12- or 24-h photoperiods, proteins in F. solani were between 1.6 and 310 kDa. For R. solani in PDB, at 0.5 dm³ min^–1 air flow and 12-h light, proteins were between 6 and 81 kDa.     

Cadmium — citric acid — xylem cell wall interactions in tomato plants

Abstract. Mutual interactions between cadmium ions, citric acid and xylem cell walls were examined. Cadmium and citric acid were measured as ¹¹⁵Cd and [1,5-¹⁴C] citric acid, respectively. Xylem cell walls were obtained by bacterial degradation of tomato stem sections (Lycopersicon esculentum Mill, cv. Tiny Tim), and applied as ion-exchange columns. The xylem column material carried 2·4 dm³ H₂O kg^?1 dry weight, and was temporarily capable of buffering perfusates at pH 5·7. Sorbed cadmium and citric acid were determined from H₂O and HCl rinses after perfusion periods. In all experiments, total cadmium and/or citric acid recoveries were better than 98%, indicating both the effectiveness of the rinses applied and the possibility of full regeneration of the xylem column. The results indicate that the presence of 2·45 mol m^?3 citric acid causes an approximately 50% reduction of adsorbed cadmium levels, irrespective of the applied total cadmium concentrations (0·04–0·4 mol m^?3 Cd(NO₃)₂.4H₂O). This reduction is probably related to a corresponding reduction to approximately 2% of the control applied free Cd²⁺ concentration, the latter also independent of the total cadmium concentrations. Furthermore, without inducing positively charged citrate complexes in the applied solution, the presence of cadmium resulted in increased levels of citric acid absorbed in the xylem column. The Donnan Free Space accumulation of citric acid in the presence of Cd(NO₃)₂.4H₂O, observed in the experiments described, could be expressed by its distribution coefficient, as approximately 15 times the control accumulation. These data indicate that the xylem column may operate as a ligand exchanger, suggesting the importance of metal ions for the longitudinal and lateral movement of organic complexing compounds in the xylem.     

Interaction between zinc nutritional status of cereals and Rhizoctonia root rot severity

An inverse correlation between plant Zn concentration and the severity of Rhizoctonia root rot, described in an earlier paper, was examined in two experiments in a growth chamber. In the first experiment, wheat (Triticum aestivum cv Songlen) was planted in a Zn deficient soil with and without added Zn, and combined factorially with different inoculum densities of Rhizoctonia solani anastomosis group 8. When Zn was added, the percentage of seminal roots infected with R. solani was significantly lower compared to the treatments without added Zn, showing that low Zn potentiated the disease. A subsequent factorial experiment of four inoculum densities and six Zn levels, (0, 0.01, 0.04, 0.1, 0.4 and 6.0 mg Zn kg^–1 soil) was conducted to investigate the Zn effect in more detail. Disease severity was markedly decreased by the higher Zn applications; the disease score dropped sharply between treatments of Zn_0.04 and Zn_0.1, a difference which was reflected in the plant yield response to Zn. For both experiments the Zn concentrations in shoots were significantly different only among Zn treatments, not among the inoculum treatments. This indicated that inoculum density or disease severity did not reduce Zn concentration in the plant. Thus, disease did not exaggerate Zn deficiency, but rather, Zn sufficiency suppressed disease severity. A potentiating link between Zn nutrition and disease severity is thereby established, although this type of experiment did not indicate the mechanism of the Zn effect.     

The effects of traits of Bacillus megaterium onseed and root colonization and their correlation withthe suppression of Rhizoctonia root rot of soybean

Bacillus megaterium strainB153-2-2 is a potential bacterial biocontrol agentagainst Rhizoctonia solani isolate 2B12(ISG-2B). To study the role of antagonism (Ant),chemotaxis (Che), motility (Mot), and sporulation(Spo) of the biocontrol agent during seed and rootcolonization and the correlation between rootcolonization and the suppression of soybean (Glycine max) root rot caused by R. solani,strain B153-2-2(Che⁺Mot⁺Ant⁺⁺Spo⁺⁺) and the sevenderived mutants with altered antagonism, chemotaxis,motility, and/or sporulation were used. The bacterialcells were introduced into soil separately either asa soybean seed coating or soil application. Two soilmixtures defined as coarse and fine soil were used. The bacterial cell chemotactic response to soybeanroot and seed exudates and antagonism to R.solani were significantly (p = 0.05) correlatedwith root and seed colonization in some but not alltreatments. The sporulation-defective mutants had lowcell populations immediately after application and,therefore, reduced root colonization. The differencesin root colonization diminished among the mutants andstrain B153-2-2 when R. solani was present inthe soil or, as seedlings grew older. Soybean seedlingroots grown in coarse soil had significantly greatercolonization by B153-2-2 or its mutants and a lowerdisease index than that in fine soil. There was asignificant positive correlation (r ² = 0.78)between root colonization by strain B153-2-2 or itsmutants and suppression of Rhizoctonia root rot.     

贵州牛角塘铅锌矿区优势植物的重金属富集特征

为筛选适合贵州喀斯特地区重金属污染土壤修复治理以及矿区生态复垦的植物材料,该研究在贵州牛角塘铅锌矿区采集30种优势植物及其根系土壤,测定其地上部、地下部和根系土壤的Cd、Cu、Ni、Pb、Zn含量,计算植物对重金属的富集和转运系数,并通过聚类分析综合评估植物的应用潜力.结果表明:(1)千里光、鬼针草地上部Cd含量高达4...     

Statistical optimization of medium components for avilamycin production by <Emphasis Type="Italic">Streptomyces viridochromogenes</Emphasis> Tü57-1 using response surface methodology

A fermentation medium for avilamycin production by Streptomyces viridochromogenes Tü57-1 has been optimized. Important components and their concentrations were investigated using fractional factorial design and Box–Behnken Design. The results showed that soybean flour, soluble starch, MgSO₄·7H₂O and CaCl₂·2H₂O are important for avilamycin production. A polynomial model related to medium components and avilamycin yield had been established. A high coefficient of determination (R ² = 0.92) was obtained that indicated good agreement between the experimental and predicted values of avilamycin yield. Student’s T-test of each coefficient showed that all the linear and quadratic terms had significant effect (P > |T| < 0.05) on avilamycin yield. The significance of tested components was related to MgSO₄·7H₂O (0.37 g/L), CaCl₂·2H₂O (0.39 g/L), soybean flour (21.97 g/L) and soluble starch (37.22 g/L). The yield of avilamycin reached 88.33 ± 0.94 mg/L (p < 0.05) that was 2.8-fold the initial yield.     

The effect of lead on photosynthesis and respiration in detached leaves and in mesophyll protoplasts of Pisum sativum

Photosynthesis and transpiration rate of detached leaves of pea (Pisum sativum L. cv. Iłowiecki) exposed to solution of Pb(NO₃)₂ at 1 or 5 mmol·dm⁻³ concentrations were inhibited. The higher concentration of this toxicant decreased photosynthesis and transpiration rates 2 and 3 times respectively, and increased respiration by about 20 %, as measured after 24 hours of treatment. Similarly to Pb(NO₃)₂, glyceraldehyde solution, an inhibitor of phosphoribulokinase, at 50 mmol·dm⁻³ concentration decreased the rates of photosynthesis and transpiration during introduction into pea leaves. The rate of dark respiration, however, remained unchanged during 2 hours of experiment. The potential photochemical efficiency of PS II (Fv/Fm) and the activity of Rubisco (EC 4.1.1.39) at 5 mmol·dm⁻³ of Pb(NO₃)₂ were lowered by 10 % and 20 % respectively, after 24 hours. Neither changes in the activity of PEPC (EC 4.1.1.31) or protein and pigment contents were noted in Pb-treated leaves. The photosynthetic activity of protoplasts isolated from leaves treated for 24 or 48 hours with Pb(NO₃)₂ at 5 mmol·dm⁻³ concentration was decreased 10 % or 25 %, whereas, the rate of dark respiration was stimulated by about 40 % and 75 %, respectively. The content of abscisic acid, a hormone responsible for stomatal closure, in detached pea leaves treated for 24 h with 5 mmol·dm⁻³ of Pb(NO₃)₂ solution was increased by about 3 times; a longer (48h) treatment led to further increase (by about 7 times) in the amount of this hormone. The results of our experiments provide evidences that CO₂ fixation in detached pea leaves, at least up to 24 hours of Pb(NO₃)₂ treatment, was restricted mainly by stomatal closure.     

Comparison ofRhizoctonia solani isolates from web blight and basal canker of cowpea and from soil

Summary Isolates ofRhizoctonia solani from web blight and stem basal canker of cowpea and those obtained from soil had similar linear growth rates on potato dextrose agar (PDA) at various temperatures but differed in other features. The web blight isolates differed from the basal canker and the soil isolates in cultural appearance on PDA and on potato marmite agar (PMA). The web blight isolates readily formed discrete sclerotia on PDA, PMA and soil but the other isolates did not. In greenhouse tests, the former were generally the most virulent in inciting foliage and stem basal necrosis and damping-off of seven crop species. Of the plants tested, the legumes were the most susceptible toR. solani.     

Availability of iron,manganese, zinc and phosphorus in submerged sodic soil as affected by amendments during the growth period of rice crop

Summary Effect of amendments, gypsum (12.5 tonnes/ha), farmyard manure (30 tonnes/ha), rice husk (30 tonnes/ha) and also no amendment (control) on the availability of native Fe, Mn and P and applied Zn in a highly sodic soil during the growth period of rice crop under submerged conditions was studied in a field experiment. Soil samples were collected at 0, 30, 60 and 90 days of crop growth. Results showed that extractable Fe (1N NH₄OAC pH 3) and Mn (1N NH₄OAC pH 7) increased with submergence upto 60 days of crop growth but thereafter remained either constant or declined slightly. Application of farmyard manure and rice husk resulted in marked improvement of these elements over gypsum and control. Increases in extractable Mn (water soluble plus exchangeable) as a result of submergence and crop growth under different amendments were accompanied by corresponding decreases in easily reducible Mn content of the soil. Application of 40 kg zinc sulphate per hectare to rice crop could substantially raise the available Zn status (DTPA extractable) of the soil in gypsum and farmyard manure treated plots while the increase was only marginal in rice husk and control plots indicating greater fixation of applied Zn. Available P (0.5M NaHCO₃ pH 8.5) behaved quite differently and decreased in the following order with crop growth: gypsum>rice husk>farmyard manure>control.     

Synthesis,characterization and antitumor activity of some metal complexes of 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones

Complexes of Mn(II), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with 3- and 5-substituted salicylaldehyde o-hydroxybenzoylhydrazones (XSBH, X = H, 3-NO₂, 3-CH₃O, 5-Cl, 5-Br, 5-CH₃ or 5-NO₂) have been prepared and characterized by elemental analysis, conductance measurements, magnetic susceptibilities (from room temperature down to liquid nitrogen temperature) and spectral studies. These studies indicate the following structures: monomeric, high-spin, distorted octahedral for Mn(XSBH)₂; monomeric, high-spin, five-coordinate for Fe(XSBH)SO₄·H₂O; dimeric, high-spin phenoxide bridged, five-coordinate for Fe(XSBH)Cl; dimeric, high-spin five-coordinate for Co(XSBH)Cl·2H₂O; dimeric low-spin, five-coordinate for Ni(XSBH)Cl·2H₂O; dimeric, four-coordinate for Zn(XSBH); and a square-planar structure for M(XSBH)Cl·H₂O (M = Cu(II) or Pt(II).Intermolecular antiferromagnetic exchange interactions are present in Fe(III) complexes, where the exchange parameter (J) is ca. −8.0 cm⁻¹ for these complexes. The Fe(III) complexes exhibit asymmetric quadrupole split doublets in their ⁵⁷Fe Mössbauer spectra. The asymmetry is found to be temperature dependent with relatively symmetrical doublets seen at low temperature. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and indicate a d_x²−y² ground state in square-planar stereo-chemistry. All these metal complexes have been screened for their antitumor activity against the P 388 lymphocytic leukaemia test system in mice and enhanced antitumor activity relative to the free ligand was found but no significant activity at the dosages used.