Sorption Characteristics of Chromium and Its Phytotoxic Effect with or without City Compost on Maize and Spinach in a Vertisol of Central India

Abstract

Phytotoxicity, due to chromium [Cr (VI)] additions from low to very high levels in a swell–shrink clayey soil (Haplustert), in maize and spinach was studied in a pot culture experiment. Six levels of Cr (VI) (0, 5, 10, 25, 50, and 75 mg kg^?1 soil) for maize and five levels for spinach (0, 2, 5, 10, and 25 mg kg^?1 soil) were applied singly and in combination with two doses (0 and 20 t ha^?1) of city compost. At levels of more than 75 mg Cr (VI) kg^?1 soil for maize there was virtually no growth after germination, whereas 25 mg Cr (VI) kg^?1 soil hindered the germination of spinach crop. Initial symptoms of Cr (VI) toxicity appeared as severe wilting of the tops of treated plants. Maize plants suffering from severe Cr (VI) toxicity had smaller roots and narrow brownish red leaves covered with small necrotic spots. In spinach, severe chlorosis was observed in leaves. Higher levels of Cr (VI) inhibited the growth and dry‐matter yield of the crops. However, application of city compost alleviated the toxic effect of Cr (VI). The concentration of Cr (VI) in plant parts increased when Cr (VI) was applied singly but decreased considerably when used in combination with city compost. There was evidence of an antagonistic effect of Cr (VI) on other heavy‐metal (Mn, Cu, Zn, and Fe) concentrations in plant tops. Thus, when Cr (VI) concentration increases, the concentration of other beneficial metals decreases. Chromium (VI) concentration in maize roots ranged from traces (control) to 30 mg kg^?1and were directly related to soil Cr (VI) concentration. At 25 mg Cr (VI) kg^?1 soil, yield of maize was reduced to 41% of control plants, whereas in spinach, 10 mg Cr (VI) kg^?1 soil caused a 33% yield reduction. Experimental results revealed that the maize top (cereal) is less effective in accumulating Cr (VI) than spinach (leafy vegetables). Laboratory studies were also conducted to know Cr (VI) sorption capacity of a swell–shrink clayey soil with and without city compost, and it was found that Cr (VI) sorption reaction was endothermic and spontaneous in nature.     

Effects of phosphogypsum or calcium sulfate on aluminon reactive aluminum in solutions at varying pH

Abstract

Growing evidence of positive crop responses to gypsum or phosphogypsum (PG) application in acid soils strongly support the use of these amendments as an ameliorant of subsoil acidity. Although gypsum improves Ca availability in subsoils, its role in alleviation of Al toxicity needs careful attention. In the current study, either PG, CaSO₄.2H₂O or CaCl₂.2H₂O was added (to supply 12 mM Ca) to solutions containing 40 μM Al at pH 4.1 + 0.1. Solution pH was gradually raised to 4.5, 4.8 and then to 5.3 at various time intervals during 25 d aging of the solutions at 25 + 1^OC.

Concentration of Al measured by aluminon method without preacidification and preheating, referred to as “reactive Al”; in this paper, was 16 μM in 2 g L^‐1PG solution without added Al. This accounted 38% of total soluble Al in PG solution. Addition of 2 g L^‐1PG to solution containing 40 μM Al, resulted in only 42% of total Al in solution present in forms reactive with aluminon. According to MINTEQ speciation model, Al in solution was present as an entirely complexed form with F^‐. An increase in solution pH up to 5.3 had no effect on measured concentration of reactive Al or predicted distribution of Al species.

Addition of CaSO₄.2H₂O to 40 μMAl solutions had no effect on the concentration of reactive Al within pH 4.1 ‐4.8, however, up to 62% of total Al was in a form complexed with SO₄ ^2‐, as predicted by MINTEQ model. The concentration of reactive Al decreased by 60% at pH 5.3. Addition of CaCl₂.2H₂O also had no effect on the concentration of reactive Al within pH 4.1 ‐ 4.8. Nearly 73 ‐ 94% of total Al was present in Al³⁺form. An increase in pH to 5.3, decreased the concentration of reactive Al by 27%. The results suggest that ion‐pairing of Al with F^‐would appear to be a possible mechanism for alleviation of Al toxicity by PG at pH range 4.1 ‐ 5.3. With regard to CaSO₄.2H₂O, at pH 4.1 ‐ 4.8 ion‐pairing with SO.₄ ^2‐appears to be possible mechanism for the alleviation of Al toxicity. In addition, at pH 5.3 a considerable decrease in reactive Al was evident which would further alleviate Al toxicity.     

Metal interactions in bush bean plants grown in a glasshouse in amended serpentine soils from California

Abstract

Bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) were grown with amendments in a glasshouse in two different serpentine soils from California. These serpentine soils are not high in Ni and Cr as in other areas of the world and the purpose of the study was to define the reasons for low plant yields in these two soils. The two soils behaved very differently. One seemed to have simple P deficiency and a mild imbalance of Ca‐Mg. The other soil appeared to have a severe Ca deficiency, the correction of which tended to increase Mg uptake also, but with improved yields. Present also seemed to be Zn, Cu, Al, Ni toxicities even though the levels of each were not high by leaf analysis tests. Stepwise regression for plants from one of the soils indicated that Cu concentration in leaves accounted for 60% of the yield variation (negative correlation), that Ca accounted for 9% more of it, and that P accounted for 13% more for a total of 82%. In the presence of low levels of Ca, some, at least, of the trace metals were toxic and Cu was one.     

Differences in shoot growth and zinc concentration of 164 bread wheat genotypes in a zinc‐deficient calcareous soil

Abstract

A greenhouse experiment was carried out to study severity of the zinc (Zn) deficiency symptoms on leaves, shoot dry weight and shoot content and concentration of Zn in 164 winter type bread wheat genotypes (Triticunt aestivum L.) grown in a Zn‐deficient calcareous soil with (+Zn=10 mg Zn kg^?1 soil) and without (‐Zn) Zn supply for 45 days. Tolerance of the genotypes to Zn deficiency was ranked based on the relative shoot growth (Zn efficiency ratio), calculated as the ratio of the shoot dry weight produced under Zn deficiency to that produced under adequate Zn supply. There was a substantial difference in genotypic tolerance to Zn deficiency. Among the 164 genotypes, 108 genotypes had severe visible symptoms of Zn deficiency (whitish‐brown necrotic patches) on leaves, while in 25 genotypes Zn deficiency symptoms were slight or absent, and the remaining genotypes (e.g., 31 genotypes) showed mild deficiency symptoms. Generally, the genotypes with higher tolerance to Zn deficiency originated from Balkan countries and Turkey, while genotypes originating from the breeding programs in the Great Plains of the United States were mostly sensitive to Zn deficiency. Among the 164 wheat genotypes, Zn efficiency ratio varied from 0.33 to 0.77. The differences in tolerance to Zn deficiency were totally independent of shoot Zn concentrations, but showed a close relationship to the total amount (content) of Zn per shoot. The absolute shoot growth of the genotypes under Zn deficiency corresponded very well with the differences in tolerance to Zn deficiency. Under adequate Zn supply, the 10 most Zn‐ inefficient genotypes and the 10 most Zn‐efficient genotypes were very similar in their shoot dry weight. However, under Zn deficiency, shoot dry weight of the Zn‐efficient genotypes was, on average, 1.6‐fold higher compared to the Zn‐inefficient genotypes. The results of this study show large, exploitable genotypic variation for tolerance to Zn deficiency in bread wheat. Based on this data, total amount of Zn per shoot, absolute shoot growth under Zn deficiency, and relative shoot growth can be used as reliable plant parameters for assessing genotypic variation in tolerance to Zn deficiency in bread wheat.     

Root cation exchange capacity of cotton cultivars in relation to aluminum toxicity

Root cation exchange capacity (CEC) was analyzed for four cotton cultivars (Pima S‐5, Stoneville 825, Deltapine 41 and Auburn 56) within tvo species (Gossypium barbadense and G. hirsutum) grown in control (O Al) and Al (1.5 mg/l) solution. Pima S‐5, a G. barbadense variety, had significantly (P < 0.10) lower root CEC than G. hirsutum cultivars in control (O Al) solution. Root CEC of Stoneville 825 was numerically but not significantly lower than Auburn 56 and Deltapine Al in control solution. Root CEC was significantly reduced in all cultivars when grown in Al solution. Compared to controls, Pima S‐5 and Stoneville 825 had either numerically or significantly less reduction in root CEC than Auburn 56 or Deltapine 41 in Al solution. Aluminum content of roots after CEC analysis was numerically greater in the former cultivars than the latter.

The lower root CEC of Pima S‐5 and Stoneville 825 in non‐toxic conditions could provide an initially greater Al tolerance when roots grow into marginally Al toxic soil. Under sustained, Al toxic conditions, root CEC becomes altered and is more of an indirect indicator of root growth as affected by as yet undetermined Al tolerance mechanism(s).

The steady‐state technique to determine root CEC virtually eliminated the inherent problems of CO. effects on pH and titrating to an end point in a specific period of time in a dynamic system.     

Hydrochars derived from sewage sludge: effects of pre-treatment with water on char properties,phytotoxicity and chemical structure

Large amounts of labile compounds are adsorbed to the surface of chars produced by hydrothermal carbonization (HTC). The aim of this study was to characterize the core and adsorbed fractions of hydrochars and to gain knowledge about the possibility to remove phytotoxic compounds by washings with water. Chars were produced by HTC of sewage sludge at different temperatures (180 – 200 °C) and over different periods of time (4 – 8 h). For comparison one pyrolysis char produced by thermocatalytic low temperature conversion (LTC) at 400 °C for 1 h was included in the study. The chars and their feedstocks were treated varying the duration (1 x 15, 1 × 30 and 1 × 60 min) and number (2 x 60 and 3 × 60 min) of washings. Physicochemical properties, including the molecular structure of the test materials, and their effects on germination and plant growth were analysed. Element concentrations and phytotoxic effects were reduced and the number of washings had a stronger effect than their length of time. Intensive washings with water reduced the hydrochars’ portion of biodegradable compounds significantly. However, also plant available nutrients were lost by washing with water, decreasing the value of hydrochars as a soil amendment.     

烟田残留除草剂药害治理研究进展

烟草是一类对除草剂较为敏感的叶类经济作物,随着除草剂的广泛应用,烟田除草剂残留问题日益严重,导致烟草植株矮化、发育迟缓、生长畸形和老叶黄化等药害症状发生,严重影响烟草质量和产量。综述了烟田土壤影响除草剂降解的环境因素、常见残留除草剂诱发的典型药害症状和烟田除草剂残留药害治理的研究进展。重点分析了烟草除草剂残留药害修复的常用传统方法(土壤翻耕、合理混配施药、灌水-排水法、酸碱中和法、喷药补救法、动物修复法)、除草剂安全剂、植物生长调节剂、抗性基因培育以及微生物降解菌的开发利用等多种方法,旨在深入研究烟田除草剂残留药害的解决方法同时为今后烟田除草剂残留药害治理创新发展提供参考。     

发酵床养猪垫料的养分转化与植物毒性研究

发酵床养殖技术也被称为原位堆肥技术,是一种值得推荐的控制畜场粪便排放与污染的生态养殖模式。本研究检测了发酵床的水分、温度和pH值变化以及在连续饲养两批猪后垫料中碳、氮和磷的组成与含量变化情况及其对植物毒性的强弱。结果表明,发酵床使用期间水分为58%-61%,垫料内部温度维持在40-55℃;在连续饲养两批猪后,垫料的pH值升高至8.16,氮、磷含量显著提高,铵态氮、亚硝态氮和硝态氮浓度显著升高,C/N比由养猪前的84∶1下降至31∶1,N/P比由2.8∶1下降至1.26∶1;垫料中的总铜浓度由7mg·kg^-1升高至89mg·kg^-1。以白菜种子作发芽试验考察废弃垫料的植物毒性,其相对发芽率为86.67%,相对根长为132.95%,发芽指数（Germination Index,GI）为115.23%,说明饲养了两批肥猪的发酵床垫料无植物毒性作用,对根的生长有促进作用,可作为有机肥还田。     

Iodine biofortification in tomato

Iodine is an essential element in the human diet, and iodine deficiency is a significant health problem. No attempts to increase iodine content in plant‐derived food (biofortification) have so far been particularly effective. We studied iodine uptake in tomato (Solanum lycopersicum L.) to evaluate whether it is possible to increase the iodine concentration in its fruits. Iodine translocation and storage inside tomato tissues were studied using radioactive iodine. Potassium iodide was also supplied at different concentrations to tomato plants to evaluate the resulting iodide concentration both in the vegetative tissues and the fruits. The results indicate that iodine was taken up better when supplied to the roots using hydroponically grown plants. However, a considerable amount of iodine was also stored after leaf treatment, suggesting that iodine transport through phloem also occurred. We found that tomato plants can tolerate high levels of iodine, stored both in the vegetative tissues and fruits at concentrations that are more than sufficient for the human diet. We conclude that tomato is an excellent crop for iodine‐biofortification programs.     

Biocontrol potential of Alternaria sp. PMK2, against a devastating weed: Parthenium hysterophorus L

Parthenium hysterophorus (Asteraceae) is known as one of the most aggressive invasive weeds, causing severe economic, environmental, human and animal health problems in India and around the world. During a series of extensive surveys for natural enemies of P. hysterophorus, a leaf spot pathogen was isolated from the affected parts of the parthenium following the standard isolation techniques using potato dextrose agar (PDA) and parthenium dextrose agar (PeDA) media. Koch's postulates were performed and found satisfactory for the isolate and proved to be pathogenic to this weed. On the basis of cultural, morphological and molecular characteristics, the pathogen was identified as Alternaria sp. PMK2. The growth of the pathogen was studied on eight selected media and it exhibited varying degrees of growth on different media. Phytotoxicity of fungal cultural filtrates was also confirmed on parthenium leaves in laboratory conditions. Due to the virulent nature of the isolated pathogen, it may be selected for further studies to develop mycoherbicide for control of this devastating weed.