Showing papers on "Phytotoxicity published in 2009"

Cadmium-induced stress on the seed germination and seedling growth of Brassica napus L., and its alleviation through exogenous plant growth regulators.

Abstract: Because of its prolific growth, oilseed rape (Brassica napus L.) can be grown advantageously for phytoremediation of the lands contaminated by industrial wastes. Therefore, toxic effect of cadmium on the germination of oilseed rape, the capability of plants for cadmium phytoextraction, and the effect of exogenous application of plant growth regulators to mitigate phytotoxicity of cadmium were investigated. For the lab study of seedlings at early stage, seeds were grown on filter papers soaked in different solutions of Cd2+ (0, 10, 50, 100, 200 and 400 μM). In greenhouse study, seedlings were grown in soil for 8 weeks, transferred to hydroponic pots for another 6 weeks growth, and then treated with plant growth regulators and cadmium. Four plant growth regulators viz. jasmonic acid (12.5 μM), abscisic acid (10 μM), gibberellin (50 μM) and salicylic acid (50 μM); and three levels of Cd2+ (0, 50 and 100 μM) were applied. Data indicated that lower concentration of Cd2+ (10 μM) promoted the root growth, whereas the severe stresses (200 or 400 μM) had negative effect on the establishment of germinating seedlings. Plants treated with any of the tested plant growth regulators alleviated cadmium toxicity symptoms, which were reflected by more fresh weight, less malondialdehyde concentration in leaves and lower antioxidant enzyme activities. The application of abscisic acid to the plants cultivated in the medium containing 100 μM Cd2+ resulted in significantly lower plant internal cadmium accumulation.

Essential oil of Artemisia scoparia inhibits plant growth by generating reactive oxygen species and causing oxidative damage.

Abstract: We investigated the chemical composition and phytotoxicity of the essential oil extracted from leaves of Artemisia scoparia Waldst. et Kit. (red stem wormwood, Asteraceae). GC/GC-MS analyses revealed 33 chemical constituents representing 99.83% of the oil. The oil, in general, was rich in monoterpenes that constitute 71.6%, with beta-myrcene (29.27%) as the major constituent followed by (+)-limonene (13.3%), (Z)-beta-ocimene (13.37%), and gamma-terpinene (9.51%). The oil and beta-myrcene were evaluated in a dose-response bioassay under laboratory conditions for phytotoxicity against three weeds-Avena fatua, Cyperus rotundus, and Phalaris minor. A significant reduction in germination, seedling growth, and dry matter accumulation was observed in the test weeds. At the lowest treatment of 0.07 mg/ml Artemisia oil, germination was reduced by 39%, 19%, and 10.6% in C. rotundus, P. minor, and A. fatua, respectively. However, the inhibitory effect of beta-myrcene was less. In general, a dose-dependent effect was observed and the growth declined with increasing concentration. Among the three weeds, the inhibitory effect was greatest on C. rotundus, so it was selected for further studies. We explored the explanation for observed growth inhibition in terms of reactive oxygen species (ROS: lipid peroxidation, membrane integrity, and amounts of conjugated dienes and hydrogen peroxide)-induced oxidative stress. Exposure of C. rotundus to Artemisia oil or beta-myrcene enhanced solute leakage, indicating membrane disintegration. There were increased levels of malondialdehyde and hydrogen peroxide, indicating lipid peroxidation and induction of oxidative stress. We conclude that Artemisia oil inhibits plant root growth through generation of ROS-induced oxidative damage.

Seasonal and annual variations of metal uptake, bioaccumulation, and toxicity in Trifolium repens and Lolium perenne growing in a heavy metal-contaminated field

Abstract: The reclamation of nonferrous metal-polluted soil by phytoremediation requires an overall and permanent plant cover. To select the most suitable plant species, it is necessary to study metal effects on plants over the time, thereby checking that metals remain stored in root systems and not transferred to aerial parts. In this purpose, the seasonal and annual variations of metal bioaccumulation, transfer, and phytotoxicity in Trifolium repens and Lolium perenne grown in a Cd-, Pb-, and Zn-contaminated soil were also studied. The experimental site was located near a closed smelter. In spring 2004, two areas were sown with T. repens and L. perenne, respectively. Thereafter, the samplings of plant roots and shoots and surrounding soils were realized in autumn 2004 and spring and autumn 2005. The soil agronomic characteristics, the Cd, Pb, and Zn concentrations in the surrounded soils and plant organs, as well as the oxidative alterations (superoxide dismutase [SOD], malondialdehyde [MDA], and 8-hydroxy-2′-deoxyguanosine [8-OHdG]) in plant organs were carried out. Whatever the sampling period, metal concentrations in soils and plants were higher than background values. Contrary to the soils, the fluctuations of metal concentrations were observed in plant organs over the time. Bioaccumulation and transfer factors confirmed that metals were preferentially accumulated in the roots as follows: Cd>Zn>Pb, and their transfer to shoots was limited. Foliar metal deposition was also observed. The results showed that there were seasonal and annual variations of metal accumulation in the two studied plant species. These variations differed according to the organs and followed nearly the same pattern for the two species. Oxidative alterations were observed in plant organs with regard to SOD antioxidant activities, MDA, and 8-OHdG concentrations. These alterations vary according to the temporal variations of metal concentrations. Metal concentrations in surrounded soils and plant organs showed the effective contamination by industrial dust emissions. Metals absorbed by plants were mainly stored in the roots. With regard to this storage, the plants seemed to limit the metal transfer to their aerial parts over the time, thereby indicating their availability for metal phytostabilization. Aerial deposition was another source of plant exposure to nonferrous metals. Despite the occurrence of metal-induced oxidative alterations in plant organs, both plant species seemed to tolerate a high metal concentration in soils. Taken together, these results indicated that T. repens and L. perenne were able to form a plant cover on highly Cd-, Pb-, and Zn-polluted soils, to limit the metal transfer to their aerial parts and were relatively metal-tolerant. All these characteristics made them suitable for phytostabilization on metal-contaminated soils. These findings also highlighted the necessity to take into account seasonal and annual variations for a future phytomanagement. In this work, the behavior of plant species grown in metal-polluted soil has been studied during 2 years. Obviously, this time is too short to ensure that metals remain accumulated in the root system and few are transferred in aerial parts over the time. It is why regular monitoring should be achieved during more than a decade after the settlement of the plant cover. This work will be completed by the study of the T. repens and L. perenne effects on mobility of metals in order to evaluate the quantities of pollutants which could be absorbed by the biota and transferred to groundwater. Bioaccessibility tests could be also realized on polluted soils in order to evaluate the phytostabilization impacts on the exposition risks for humans.

Photosynthesis and growth responses of pea Pisum sativum L. under heavy metals stress.

Abstract: The present work aimed to study the physiological e ects of cadmium (Cd) and copper (Cu) in pea (Pisum sativum). Pea plants were exposed to increasing doses of cadmium chloride (CdCl2) and copper chloride (CuCl2) for 20 d. The examined parameters, namely root and shoot lengths, the concentration of photosynthetic pigments and the rate of photosynthesis were a ected by the treatments especially with high metals concentrations. The analysis of heavy metals accumulation shows that leaves significantly accumulate cadmium for all the tested concentrations. However, copper was significantly accumulated only with the highest tested dose. This may explain the higher inhibitory e ects of cadmium on photosynthesis and growth in pea plants. These results are valuable for understanding the biological consequences of heavy metals contamination particularly in soils devoted to organic agriculture.

Chromium (VI) induced phytotoxicity and oxidative stress in pea (Pisum sativum L.): biochemical changes and translocation of essential nutrients.

Abstract: Due to widespread industrial use, chromium (Cr) is considered a hazardous environmental pollutant. It is known to inhibit plant growth and development. The present study provides the evidence of the phytotoxicity of this metal on the pea (Pisum sativum L. cv Azad) plants. The plants of pea (Pisum sativum L.) were grown in refined sand under different concentrations i.e. 0.05, 0.1, 0.2, 0.3 and 0.4 mM of Cr (VI) in order to study the effect on growth and yield, photosynthetic pigments, relative water content, non-reducing sugar and protein with activity of certain enzymes like catalase, peroxidase, starch phosphorylase and ribonuclease. The analysis of the results showed that photosynthetic pigments (68.68%), relative water contents (62.77%), non-reducing sugar (66.66%) and protein (81.57%) were decrease along with reduction in plant height (52.69%) and leaf area (50.81%) of the pea plants. However, in response to various concentration of Cr exposed plants showed significant induction of reducing and total sugars with enzymes like catalase, starch phosphorylase and ribonuclease. The translocation of Cr in various part of pea plant have been found in order of root> stem> leaves>seeds which ranged between 34.8 to 217.3 mg g(-1) d.wt. (dry weight) in roots, 6.5 to 173.13 mg g(-1) d.wt. in shoot, 4.2 to 74.43 mg g(-1) d.wt. in leaves and 0.94 to 8.64 mg g(-1) d.wt. in seeds, that is also reflected by the transfer factor of Cr from refined sand to tested species.

Phytotoxicity of fluoride in the germination of paddy (Oryza sativa) and its effect on the physiology and biochemistry of germinated seedlings.

Abstract: This study reports the influence of 0, 10, 20, and 30 mg/L sodium fluoride (NaF) on paddy (rice, Oryza sativa) seeds and seedlings. After 15 days of treatment with 0 and 10 mg NaF/L, 100% germination occurred, but at 20 and 30 mg NaF/L, germination was reduced to 96 and 92%, respectively. Physiological parameters, viz., root length, shoot length, and dry weight decreased monotonically with increasing NaF concentration. At 30 mg NaF/L the average root length, shoot length, and dry weight were reduced to 50%, 27%, and 29%, respectively. The chlorophyll content of the leaves also decreased monotonically, but the reducing sugar and ascorbic acid content initially decreased and then increased with increasing concentration of NaF. Uptake of fluoride in the whole plant body increased with increasing levels of NaF; at 10 mg NaF/L the accumulation was less than 75 mg/kg dry mass, but at 20 mg/L NaF it increased to ca. 2000 mg/kg and double this level at 30 mg/L NaF.

Response of potted grapevines to increasing soil copper concentration.

Abstract: Background and Aims: Copper accumulation in soil may promote phytotoxicity in grapevines. Nutritional implications of potted vines to increasing concentrations of copper (Cu) in either clay loam soil or clay loam soil mixed with 85% sand were tested on Vitis vinifera (L.) cv Sangiovese and crop toxicity threshold and symptoms determined. Methods and Results: Soils were mixed at planting with Cu at the rates (mg Cu/kg) of 0 (control, native soil Cu only), 50, 100, 200, 400, 600, 800 and 1000, and non-bearing vines were grown in these for two seasons. Reduction of root growth was observed after addition of ?400 mg Cu/kg to both soils; reduction of shoot growth, leaf number and chlorosis of leaf edges were detected only in sand-enriched soil. Root Cu concentration increased in response to soil Cu addition. Unlike that of leaf Cu and N, the amount of P and Fe (in both soils) and Mg and Ca (in sand-enriched soil only) were reduced by soil Cu. Conclusion: Vines grown in sand-enriched soil tolerated lower concentrations of Cu than in clay loam soil, probably because of the lower nutritional status and the higher root Cu concentration. Significance of the Study: Results provide information on the concentration of soil Cu that grapevine can tolerate and on the nutrients involved in the response to toxic levels of soil Cu in clay loam and sandy clay loam soils.

Lavender as a source of novel plant compounds for the development of a natural herbicide.

Abstract: In a previous study, lavender (Lavandula spp.) was found to be highly phytotoxic towards annual ryegrass (Lolium rigidum, ARG), a major weed of winter wheat crops in Australia. This research aimed to further explore this relationship and determine the chemical(s) responsible for the observed effect. In bioassay, it was determined that the stem and leaf extract of L. x intermedia cv. Grosso ranked highest and had the potential to reduce significantly the root growth of several plant species. An extract concentration of 10% almost completely inhibited ARG root growth. When the extract was tested for stability, there was no loss in phytotoxicity after the 256 day trial. Via bioassay-guided fractionation and chromatographic techniques, it was determined that the sub-fraction consisting of coumarin and 7-methoxycoumarin was most phytotoxic towards ARG. Chemoassays of 18 structural analogues of coumarin showed that coumarin itself was the most phytotoxic and largely responsible for the observed phytotoxicity of the extract. Soil trials were conducted using pure coumarin and the lavender extract, and in both instances, shoot length and weight were significantly reduced by post-emergence application at all concentrations evaluated.

Response of wheat to foliar and soil application of urea at different growth stages.

Abstract: A field experiment was conducted to evaluate the effect of foliar application of urea applied in different concentrations and at different stages on yield and yield components of wheat (Triticum aestivum L) cv. “Kiran-95” under agro-climatic condition of Sindh. The experiment was laid out according to randomized complete block design having two factors with four repeats. Six concentrations of urea i.e., 0, 2, 4, 6, 8 and 10% as foliar application along with 60 and 120 kg N ha -1 were applied as soil application. The results revealed that foliar application of urea significantly increased plant height, spike length, number of grains spike -1 , hundred grain weight, biological yield, grain yield and N uptake by the crop. The foliar spray of 4% urea solution was found to be most effective for enhancing the quantitative and qualitative traits when sprayed at tillering, stem elongation and boot stage. The grain yield was increased by 32% when 4% urea solution was applied as foliar spray. Further increase in the concentrations of urea spray was not found to be useful and economical as it declined the grain yield by 25% or even more probably due to its toxicity.

Development of a laboratory bioassay and effect of soil properties on sulfentrazone phytotoxicity in soil.

Abstract: Sulfentrazone is a phenyl triazolinone herbicide used for control of certain broadleaf and grass weed species. Sulfentrazone persists in soil and has residual activity beyond the season of application. A laboratory bioassay was developed for the detection of sulfentrazone in soil using root and shoot response of several crops. Shoot length inhibition of sugar beet was found to be the most sensitive and reproducible parameter for measurement of soil-incorporated sulfentrazone. The sugar beet bioassay was then used to examine the effect of soil properties on sulfentrazone phytotoxicity using 10 different Canadian prairie soils. Concentrations corresponding to 50% inhibition (I50 values) were obtained from the dose–response curves constructed for the soils. Sulfentrazone phytotoxicity was strongly correlated to the percentage organic carbon (P = 0.01) and also to percentage clay content (P = 0.05), whereas correlation with soil pH was nonsignificant (P = 0.21). Because sulfentrazone phytotoxic...