Showing papers on "Phytotoxicity published in 2006"
TL;DR: The data revealed that the plants exposed to NiCl2 in soil bioaugmented with strain SJ-101 have accumulated 0.147% Ni vis-à-vis 0.094% accumulation in dry biomass of the plants grown in uninoculated soil, suggesting the strain could be exploited for bacteria-assisted phytoaccumulation of this toxic heavy metal from contaminated sites.
486 citations
TL;DR: The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m3 ha−1 OMW, however, after 42 days' incubation, a complete recovery of the soil Germination capability and a residual phyttoxicity of about 30% were observed.
Abstract: Olive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g −1 soil of OMW (corresponding to a field rate of 0, 40 and 80 m 3 ha −1 , respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, β-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m 3 ha −1 OMW. After 42 days' incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m 3 ha −1 OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms.
207 citations
TL;DR: An unexpectedly widespread occurrence of phytotoxicity with clear dynamic patterns during the decomposition processes of plant materials is demonstrated and the ecological consequences of this might have been underestimated.
Abstract: Summary
• Allelopathic effects of plant litter have been extensively studied, but less attention has been given to the dynamics of phytotoxicity during the decomposition processes.
• Decomposition experiments were carried out on above- and below-ground plant materials of 25 species of different functional groups (nitrogen fixer, forbs, woody and grasses–sedges) in aerobic and anaerobic conditions. The phytotoxicity of aqueous extracts of decomposing material was assessed by bioassay in 30 d of laboratory and 90 d of litterbag decomposition experiments.
• Phytotoxicity was widespread with c. 90% of the tested species showing significant phytotoxic releases. Phytotoxicity largely varied between different plant functional groups (nitrogen fixer > forbs = woody >> grasses–sedges) and was higher for leaf compared with root materials. In all species tested during decomposition, phytotoxicity rapidly decreased in aerobic conditions but sharply increased and became stable in anaerobic conditions.
• The results demonstrate an unexpectedly widespread occurrence of phytotoxicity with clear dynamic patterns during the decomposition processes of plant materials. The ecological consequences of this might have been underestimated.
193 citations
TL;DR: The results suggested that Cu toxicity to the plant was at least partly due to an influence on N metabolism, and interactive effects between Cu exposure and N level on plant biomass, root/shoot ratio, and chlorophyll and nitrate content in leaves were suggested.
150 citations
TL;DR: The sludge extracts had significant adverse effect on the germination index (GI) of barley and cress, a fact which indicates that some characteristics affected root growth.
147 citations
TL;DR: Growth of aphid populations on plants treated with a MJ–BTH mixture was reduced almost as much as with treatments of MJ alone, suggesting that antagonism between JA‐dependant and SA‐dependent plant signaling pathways is only mild with regard to induced defenses against aphids.
Abstract: Recent advances in the understanding of plant signaling pathways have opened the way for using elicitor-induced plant resistance as a tactic for protecting plants against arthropod pests. Four common elicitors of induced responses in tomato, Lycopersicon esculentum Mill. (Solanaceae), were evaluated with regard to phytotoxicity, induction of plant defensive proteins, and effects on population growth and fecundity of a common pest, the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae). Ethephon and methyl jasmonate (MJ) treatments caused varying degrees of phytotoxicity. Ethephon caused pronounced changes in plant growth form and severe, dose-dependent negative impacts on plant growth and flowering. Effects with MJ were milder, but still caused temporary inhibition of development, leading to smaller plants and delayed flowering. The commercial elicitors benzothiadiazole (BTH) and harpin did not cause detectable phytotoxicity. The highest doses of ethephon and MJ significantly increased leaf peroxidase (POD) levels but only MJ treatments significantly increased polyphenol oxidase (PPO) levels. BTH and harpin had no detectable effects on POD and PPO. Populations of green peach aphids grew significantly more slowly on plants treated with BTH or MJ than on control plants or plants treated with harpin or ethephon. Slowed aphid population growth on BTH-treated plants was due to significant reductions in aphid fecundity, although this was independent of changes in time to onset of reproduction or time to death. Aphid fecundity was also reduced on MJ-treated plants relative to controls, but this difference was not statistically significant, suggesting that other mechanisms are involved in slowing aphid population growth on MJ-treated plants. Growth of aphid populations on plants treated with a MJ-BTH mixture was reduced almost as much as with treatments of MJ alone, suggesting that antagonism between JA-dependant and SA-dependent plant signaling pathways is only mild with regard to induced defenses against aphids.
135 citations
TL;DR: In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings as mentioned in this paper, and this treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to −1 dry weight.
131 citations
TL;DR: The original, untreated OME was stronglyphytotoxic to lettuce seeds even after several dilutions with water; however, phytotoxicity decreased considerably following treatment with lime and cationic poly-electrolytes; this was attributed to the removal of phenols and other phytOToxic species from the liquid phase.
125 citations
TL;DR: The maturing process of cattle manure composting was characterized by elemental composition analysis, solid-state 13 C NMR spectra, respiratory quinone profiles, and a germination index using Brassica campestris L. as mentioned in this paper.
100 citations
TL;DR: Oil from senescent and juvenile leaves being rich in citronellal could be used as commercial source of citroneLLal whereas that from adult leaves for weed management programmes as it was the most phytotoxic.
Abstract: A total of 23 volatile constituents was identified and characterized by GC and GC-MS in the volatile essential oil extracted from intact (juvenile and adult) and fallen (senescent and leaf litter) leaves of lemon-scented eucalyptus (Eucalyptus citriodora Hook.). The leaves differed in their pigment, water and protein content, and C/N ratio. The oils were, in general, monoterpenoid in nature with 18 monoterpenes and 5 sesquiterpenes. However, a great variability in the amount of essential oils and their individual constituents was observed in different leaf tissues. The amount was maximum in the senescent leaves collected from the floor of the tree closely followed by that from juvenile leaves. In all, 19 constituents were identified in oil from juvenile and senescent leaves compared to 23 in adult leaves and 20 in leaf litter, respectively. Citronellal, a characteristic monoterpene of the oil reported hitherto was found to be more (77-78%) in the juvenile and senescent leaves compared to 48 and 54%, respectively, in the adult leaves and leaf litter. In the adult leaves, however, the content of citronellol--another important monoterpene-- was very high (21.9%) compared to other leaf types (7.8-12.2%). Essential oil and its two major monoterpenes viz. citronellal and citronellol were tested for their phytotoxicity against two weeds (Amaranthus viridis and Echinochloa crus-galli) and two crops (Triticum aestivum and Oryza sativa) under laboratory conditions. A difference in the phytotoxicity, measured in terms of seedling length and dry weight, of oil from different leaves and major monoterpenes was observed. Oil from adult leaves was found to be most phytotoxic although it occurs in smaller amount (on unit weight basis). The different toxicity of different oil types was due to the relative amount of individual monoterpenes present in the oil, their solubility and interactive action. The study concludes that oil from senescent and juvenile leaves being rich in citronellal could be used as commercial source of citronellal whereas that from adult leaves for weed management programmes as it was the most phytotoxic.
96 citations
TL;DR: The results of this study newly demonstrate significant toxicity of NPAHs to plants and demonstrate suitability of multiple biomarker assessment to characterize mechanisms of oxidative stress and to serve as an early warning of phytotoxicity in vivo.
Abstract: N-heterocyclic derivatives of polycyclic aromatic hydrocarbons (NPAHs) are widespread concomitantly with their parent analogues and have been detected in air, water, sediments, and soil. Although they were shown to be highly toxic to some organisms, our understanding of their occurrence, environmental fate, biological metabolism, and effects is limited. This study evaluated toxic effects of three homocyclic aromatic hydrocarbons (PAHs-phenanthrene, anthracene, fluorene) and their seven N-heterocyclic derivates on higher terrestrial plants Sinapis alba, Triticum aestivum, and Phaseolus vulgaris. Germinability, morphological endpoints, parameters of detoxification, and antioxidant components of plant metabolism as well as lipid peroxidation were studied in acute phytotoxicity tests. Phytotoxicity of NPAHs was generally more pronounced than the effects of parent PAHs, and it significantly differed with respect to the structure of individual NPAHs. Sinapis alba and T. aestivum were more sensitive plant species than P. vulgaris. Chemicals with the strongest inhibition effect on germination and growth of plants were phenanthridine, acridine, benzo[h]quinoline, and 1,10- and 1,7-phenanthroline. All tested chemicals significantly induced activities of detoxification and antioxidant enzymes (glutathione reductase, glutathione peroxidase, and glutathione-S-transferase) at nanomolar to low micromolar concentrations. Levels of reduced glutathione were induced by all tested chemicals except 1,10- and 4,7-phenanthroline. Furthermore, fluorene, carbazole, acridine, phenanthrene, phenanthridine, benzo[h]quinoline, and 1,7-phenanthroline significantly increased lipid peroxidation. The results of our study newly demonstrate significant toxicity of NPAHs to plants and demonstrate suitability of multiple biomarker assessment to characterize mechanisms of oxidative stress and to serve as an early warning of phytotoxicity in vivo.
TL;DR: The results show beneficial effects using treated olive mill wastewater, and the treated plants showed an improvement in seed biomass, spike number, plant growth, and a similar or even better dry productivity than plants irrigated with water.
Abstract: The effects of untreated and treated olive mill wastewater on seed germination, plant growth and soil fertility were studied. Tomato (Lycopersicon esculentum), chickpea (Cicer arietinum), bean (Viciafaba), wheat (Triticum durum) and barley (Hordeum vulgare) were tested for the germination index and growth in soil irrigated by olive mill wastewater. Lepidium sativum was used as the standard species for the germination index and phytotoxicity evaluation. We measured soil properties, crop growth, herbage biomass, leaf elongation and productivity. The results show beneficial effects using treated olive mill wastewater. The treated plants showed an improvement in seed biomass, spike number, plant growth, and a similar or even better dry productivity than plants irrigated with water, e.g. Hordeum vulgare 102%, Triticum durum 105%, Cicer arietinum 101% and Viciafaba 102%. An increase in the germination index from 100% to 115% was observed. Soil organic matter, respiration and enzymatic activities were also enhanced by treated olive mill wastewater ferti-irrigation. However, even diluted 10 times, untreated olive mill wastewater inhibited the species germination, e.g. 1.2% for Hordeum vulgare and 40% for Cicer arietinum and Viciafaba, and plant growth (16-42.5%). Leaf necrosis and low productivity were observed in crops ferti-irrigated by untreated olive mill wastewater.
TL;DR: Arsenate phytotoxicity decreased significantly after aging for three months, although the extent of aging differed among soils, indicating that arsenate adsorption was a key factor controlling its bioavailability.
Abstract: Bioavailability of As varies among soils, and this needs to be taken into account during environmental risk assessment. Using a standardized barley root elongation assay, we investigated the phytotoxicity of arsenate added to 16 European soils that varied widely in their physicochemical properties. The effective concentrations of As causing 10% (EC10) and 50% (EC50) inhibition were estimated based on the concentrations of total added As or As extracted with 0.05 M (NH4)2SO4 or 0.05 M NH4H2PO4. In addition, four soils were used to evaluate changes in arsenate phytotoxicity over a three-month period. The EC10s and EC50s of added As varied from 4.2 to 206.7 mg/kg and from 26.6 to 458.2 mg/kg, respectively. Multiple-regression analysis showed that the variability in the EC10 and EC50 was largely (>89%) explained by the contents of amorphous Mn oxide and clay and, to a lesser extent, Fe oxide, indicating that arsenate adsorption was a key factor controlling its bioavailability. Neither (NH4)2SO4 nor NH4H2PO4 extraction could explain arsenate phytotoxicity independently of soil properties. Furthermore, arsenate phytotoxicity decreased significantly after aging for three months, although the extent of aging differed among soils. This aging effect should be taken into account during the risk assessment.
TL;DR: The first report of potential allelopathic activity of steroids on weeds based on their phytotoxicity is reported, and eight compounds were isolated for the first time in Oryza sativa.
TL;DR: It is concluded that the initial biochemical reaction to salinity at protein level in wheat is an unspecific response and not a specific adaptation toSalinity.
Abstract: Salinity has a two-phase effect on plant growth, an osmotic effect due to salts in the outside solution and ion toxicity in a second phase due to salt build-up in transpiring leaves. To elucidate salt-resistance mechanisms in the first phase of salt stress, we studied the biochemical reaction of salt-resistant and salt-sensitive wheat (Triticum aestivum L.) genotypes at protein level after 10 d exposure to 125 mM-NaCl salinity (first phase of salt stress) and the variation of salt resistance among the genotypes after 30 d exposure to 125 mM-NaCl salinity (second phase of salt stress) in solution culture experiments in a growth chamber. The three genotypes differed significantly in absolute and relative shoot and root dry weights after 30 d exposure to NaCI salinity. SARC-1 produced the maximum and 7-Cerros the minimum shoot dry weights under salinity relative to control. A highly significant negative correlation (r2 = -0.99) was observed between salt resistance (% shoot dry weight under salinity relative to control) and shoot Na + concentration of the wheat genotypes studied. However, the salt-resistant and salt-sensitive genotypes showed a similar biochemical reaction at the level of proteins after 10 d exposure to 125 mM NaCI. In both genotypes, the expression of more than 50% proteins was changed, but the difference between the genotypes in various categories of protein change (up-regulated, down-regulated, disappeared, and new-appeared) was only 1 %-8%. It is concluded that the initial biochemical reaction to salinity at protein level in wheat is an unspecific response and not a specific adaptation to salinity.
TL;DR: The most active compounds were the synthetic benzoxaz inone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazIn-3-one, with highly significant inhibition on the development of both weeds.
Abstract: Avena fatua L. (wild oat) and Lolium rigidum Gaud. (rigid ryegrass) are highly problematic weeds affecting a wide variety of cereal crops worldwide. The fact that both of these weeds have developed resistance to several herbicide groups made them optimal candidates as target organisms for ongoing research about the potential application of allelochemicals and analogue compounds as natural herbicide models. Benzoxazinones, a family of natural allelochemicals present in corn, wheat, and rye, including 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one, together with some degradation products, found in crop soils as well as in other systems, and some synthetic analogues of them were tested on wild oat and rigid ryegrass seeds; the results were statistically treated, and some structure-activity relationships, useful in further development of natural herbicide models, were elucidated. The most active compounds were the synthetic benzoxazinone 2-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one and the degradation product 2-aminophenoxazin-3-one, with highly significant inhibition on the development of both weeds. The ecological role of these compounds is discussed by considering both degradability and phytotoxicity. The bioactivity of aminophenoxazines has been correlated by their aqueous solubility-lipophilicity predicted by means of computational methods.
TL;DR: In the present study, the critical concentration of La for rice relative to environmental safety was suggested to be 42.03 mg kg(-1) in red soil and 83.33 mg kg−1 in paddy soil.
TL;DR: The study demonstrated that the Phytotoxkit microbiotest was effective in identifying toxic samples, however, sediment organic matter content and grain‐size distribution had a significant impact on both sediment contamination and higher plantresponses to contaminated samples.
Abstract: The main objective of the research was to evaluate the suitability of the Phytotoxkit microbiotest as a tool for hazard assessment of sediments. The concentrations of oil derivatives, polycyclic aromatic hydrocarbons (PAHs), and heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were determined in sediment samples collected from the urban canal in Opole (Poland), in order to obtain a general insight of the level of sediment contamination. Phytotoxicity of sediments was estimated on the basis of seed germination and root elongation measurements, combined into an overall germination index (Gl). The results revealed spatial and vertical differentiation in sediment contamination. A good correlation was obtained between organic matter content and the concentrations of particular sediment pollutants. Values of correlation coefficients at P < 0.05 ranged from 0.3246 for oil derivatives to 0.8929 for PAHs. Phytotoxicity tests, carried out on the monocotyl Sorghum saccharatum and the dicotyls Sinapis alba and Lepidium sativum, showed different responses of the three plant species to sediment samples ranging from growth inhibition to growth stimulation. The Gl values revealed the following increasing order of plant sensitivity to contaminated sediments: L. sativum < S. alba < S. saccharatum. The study demonstrated that the Phytotoxkit microbiotest was effective in identifying toxic samples. However, sediment organic matter content and grain-size distribution had a significant impact on both sediment contamination and higher plant responses to contaminated samples. The implication of these findings are discussed.
TL;DR: Results show that phenol removal by the laccase activity of white-rot fungi can be important in the elimination of phytotoxic substances present in olive-mill dry residues.
Metz1
TL;DR: For cadmium-soil contamination, the determination of quantitative sensitivity relationships (QSR) between classical and antioxidative enzyme biomarkers showed that the most sensitive plant species have, generally, the lowest QSR values.
TL;DR: In this paper, the authors examined a possible involvement of boron (B) in the detoxification of aluminum by stimulating glutathione (GSH) metabolism, a mechanism essential for the resistance of plants under stress conditions.
Abstract: Ionic stress caused by high aluminum (Al) concentrations is one of the most widespread phytotoxicity problems globally in agricultural regions, greatly limiting crop yield in affected areas. The objective of this work was to examine a possible involvement of boron (B) in the detoxification of Al by stimulating glutathione (GSH) metabolism, a mechanism essential for the resistance of plants under stress conditions. Our results clearly demonstrate that increased application of B in the presence of high Al concentrations in the growth medium stimulates GSH biosynthesis, suggesting it could be an effective strategy to combat stress associated with the formation of active-oxygen species (AOS). In the specific case of Al toxicity, B reduces phytotoxicity by stimulating leaf biosynthesis of GSH and an increase in its concentration in the roots. Therefore, in this work, we also identify GSH metabolism as one of the key processes in Al detoxification. Finally, our results imply that greater B application leads to a greater resistance to Al toxicity, a fact that might be significant for higher productivity of agricultural plants grown in acid soils.
TL;DR: Weathering and aging of energetic materials in soil significantly decreased theoxicity of TNT, TNB or 2,6-DNT to Japanese millet or ryegrass based on seedling emergence, but significantly increased the toxicity of all four EMs to all three plant species based on shoot growth.
TL;DR: In ongoing research about the structure-activity relationships of benzoxazinones and the structural requirements for their phytotoxicity enhancement and after characterization of the optimal structural features, a new generation of chemicals with enhanced lipophilicity was developed.
Abstract: Benzoxazinones are plant allelochemicals well-known for their phytotoxic activity and for taking part in the defense strategies of Gramineae, Ranunculaceae, and Scrophulariceae plants. These properties, in addition to the recently optimized methodologies for their large-scale isolation and synthesis, have made some derivatives of natural products, 2,4-dihydroxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIBOA) and its 7-methoxy analogue (DIMBOA), successful templates in the search for natural herbicide models. These new chemicals should be part of integrated methodologies for weed control. In ongoing research about the structure-activity relationships of benzoxazinones and the structural requirements for their phytotoxicity enhancement and after characterization of the optimal structural features, a new generation of chemicals with enhanced lipophilicity was developed. They were tested on selected standard target species and weeds in the search for the optimal aqueous solubility-lipophilicity rate for phytotoxicity. This physical parameter is known to be crucial in modern drug and agrochemical design strategies. The new compounds obtained in this way had interesting phytotoxicity profiles, empowering the phytotoxic effect of the starting benzoxazinone template in some cases. Quantitative structure-activity relationships were obtained by bioactivity-molecular parameters correlations. Because optimal lipophilicity values for phytotoxicity vary with the tested plant, these new derivatives constitute a more selective way to take advantage of benzoxazinone phytotoxic capabilities.
TL;DR: In this paper, the mechanism by which calcium alleviates manganese (Mn) phytotoxicity in barley plants was clarified by growing barley plants under the following conditions: (1) a nutrient solution alone (control), (2) nutrient solution + 25 μM Mn (mn-toxic), and (3) a 25 μ M Mn + 20 mM Ca (Ca-alleviated).
Abstract: In order to clarify the mechanism by which calcium (Ca) alleviates manganese (Mn) phytotoxicity, barley plants were grown under the following conditions: (1) nutrient solution alone (control), (2) nutrient solution + 25 μM Mn (Mn-toxic), and (3) nutrient solution + 25 μ M Mn + 20 mM Ca (Ca-alleviated). Feeding experiments using 54Mn and 59Fe (iron) with 2.0 or 20 mM Ca to the plant roots were also conducted. The absorption and translocation of 54Mn in the control plants were lowered by the high-Ca (20 mM) feeding condition. The translocation of 54Mn to shoots of Mn-toxic or Ca-alleviated plants was also lowered by the high-Ca feeding condition, but 54Mn absorption by roots of the plants was unaffected. The absorption and translocation of 59Fe in the plants was unaffected by the high-Ca feeding condition. Calcium alleviation of Mn phytotoxicity in barley may be induced mainly by the inhibition of Mn translocation to shoots.
TL;DR: Results suggest that imazamox sprayed at normal field application rates can pose slight risks of carry-over of residues, which may damage very sensitive species (sugar beet, oilseed rape and spinach) in sandy soils.
Abstract: Summary Greenhouse bioassays were carried out from 1999 to 2002 on several types of soils of central Italy to assess the carry-over risk of imazamox residues to non-target crops No observable effect levels (NOELs) were determined on quartz sand; sugar beet showed the highest sensitivity to imazamox (NOEL 04–08 ng ai mL )1 of substrate), followed by spinach, oilseed rape, fennel, cauliflower and lettuce (NOELs from 1 to 5 ng ai mL )1 of substrate) Wheat, sunflower, grain sorghum and maize were not very sensitive to this herbicide Imazamox availability was greatest on sandy soils and decreased in soils with high clay or organic carbon content, where herbicide efficiency was less than 50%, with respect to non-sorptive media The decline of herbicide efficiency was quick in sandy soils, where herbicide efficiency dropped to 50% in less than 3 days In clay-loam or organic soils, 50% relative efficiency was reached in 15–33 days Such results suggest that imazamox sprayed at normal field application rates can pose slight risks of carry-over of residues, which may damage very sensitive species (sugar beet, oilseed rape and spinach) in sandy soils In these cases, safe recropping intervals of 1–3 months are required, so current label guidelines for imazamox are adequate to protect rotational vegetable crops in central Italy
TL;DR: In this paper, the effect of soil amended with sugarcane straw leachate and its constituents on root elongation of weed and crop plants was investigated through assays in both autoclaved soil and sand.
Abstract: The present study investigates the effect of soil amended with sugarcane straw leachate and its constituents on root elongation of weed and crop plants. The influence of soil biotic and abiotic factors on plant growth were also evaluated through assays in both autoclaved soil and sand. In unsterile soil, straw leachates stimulated root growth of some test plants at 6 g dry straw ls−1 and inhibited root elongation at higher concentrations. A bioassay guided process of the bioactive leachate constituents led to the isolation of vanillic, syringic and ferulic acids. These compounds were also assayed on the test plants in the three mentioned substrates. In unsterile soil, phenolics stimulated the growth of some species at 19 mg l−1. Higher phenolics concentrations were inhibitory. The concentration needed to inhibit 25% root elongation (EC25) was calculated from the dose–response curves. The concentration of phenolics in the leachate (64 g dry straw l−1) was estimated to be 187 mg l−1 (ferulic acid), 131 mg l−1 (vanillic acid) and 20 mg l−1 (Syringic acid). In general, these concentrations were below the EC25 values determined in unsterile soil indicating that these compounds cannot completely explain the strong inhibitory activity of sugarcane straw leachates. The role of soil factors on phytotoxicity of sugarcane straw leachate and its identified growth regulators is also discussed.
TL;DR: Results indicate that the Al-induced secretion of organic acids from Atlas66 roots has a positive correlation with Al tolerance, and comprehensive treatment of Al3+ and H+ indicates that wheat is adversely influenced by excess Al3+, rather than low pH.
Abstract: Phytotoxicity of aluminum (Al) has become a serious problem in inhibiting plant growth on acid soils. Under Al stress, the changes of rhizosphere pH, root elongation, absorption of Al by wheat roots, organic acids exuded from roots, and some main factors related to Al-tolerant mechanisms have been studied using hydroponics, fluorescence spectrophotometry, and high performance liquid chromatography (HPLC). Two wheat cultivars, Brevor and Atlas66, differing in Al tolerance are chosen in the study. Accordingly, the rhizosphere pH has a positive effect on Al tolerance. Atlas66 (Al-tolerant) has higher capability to maintain high rhizosphere pH than Brevor (Al-sensitive) does. High pH can reduce Al3+ activity and toxicity, and increase the efficiency of exuding organic acids from the roots. More inhibition of root elongation has been found in Brevor because of the exposure of roots to Al3+ solution at low pH. Brevor accumulate more Al in roots than Atlas66 even at higher pH. Al-induced exudation of malic and c...
TL;DR: In this article, surface waters were analysed with a PAM fluorometry-based bioassay that employs the photosynthetic efficiency (photosystem II quantum yield) of laboratory cultured microalgae, as an endpoint measure of phytotoxicity.
TL;DR: In this paper, a study was conducted to find out the phytotoxic effect of invasive weed Ageratum conyzoides on chickpea (Cicer arietinum).
01 Jan 2006
TL;DR: A study was conducted to find out the phytotoxic effect of invasive weed Ageratum conyzoides on chickpea (Cicer arietinum), and weed residues amended in the soil significantly reduced the chickPEa growth.
Abstract: A study was conducted to find out the phytotoxic effect of invasive weed Ageratum conyzoides on chickpea (Cicer arietinum). Weedresidues amended in the soil significantly reduced the chickpea growth. Root length, plant height and biomass of chickpea were lower in thesoilsamendedwithbelow-orabove-groundweedresidues.Inaddition,comparedtocontrol,thenodulation(nodulenumber,theirweightandleghemoglobin content) of chickpea was also reduced in the amended soils. The observed reduction in chickpea growth and nodulation wasattributed to the presence of phytotoxic phenolics in the residues.# 2005 Elsevier B.V. All rights reserved. Keywords: Residues; Phytotoxicity; Plant growth; Root nodules; Leghemoglobin content; Phenolics 1. IntroductionAgeratum conyzoides L. (Billy goat weed; familyAsteraceae), a native of tropical America has now spreadtovarioustropicalandsubtropicalpartsoftheworldincludingIndia. It is an aromatic, annual weed of cultivated fields, butalso invades other ecosystems such as pastures, grasslands,wastelandsandevenforestareas.Intheagriculturalfields,itisvery troublesome, interferes with the growth and establish-ment of crops and reduces their yield (Bansal, 1988). Thesuccessful invasion of A. conyzoides is attributed to its widerange of environmental adaptability, higher reproductivepotentialandallelopathy.Asregardsitsallelopathicpotential,preliminary reports indicate that aqueous leaf, root andrhizospheresoilextractsinhibitthegrowthofotherplants(Jhaand Dhakal, 1990; Singh et al., 2003). Even, essential oilsextracted from the weed are inhibitory and suppress plantgrowth (Kong et al., 1999). In northwestern India, A.conyzoides is very common in thewheat and chickpea fieldsduringthewinterseasonandadverselyaffectsthecropgrowth(Bansal,1988).StudieshavedemonstratedthatA.conyzoidesaffects wheat growth by releasing water-soluble allelochem-icals into the immediate soil medium (Singh et al., 2003).However,nostudyhasbeendonetodetermineitsphytotoxiceffectonthegrowthofchickpea,whichisgenerallygrowninthe infested fields after manual removal of the weed. It ishypothesized that left over weed residues gradually mix intothe soil upon ploughing and/or decomposition, releasephytotoxicprinciplesandinterferewiththechickpeagrowth.To explore this, a study was therefore planned to assess theimpactofA.conyzoidesresiduesonthegrowthandnodulationof chickpea.2. Material and methodsResidues of A. conyzoides were collected from the weedinfested fields and brought to the laboratory. These wereshade dried, separated into above- and below-groundportions, powdered and filled into polyethylene bags.To study the phytotoxic impact of weed residues, soil was