Comparative assessment of two biodegradable chelants, S,S-ethylenediamine disuccinic acid and nitrilotriacetic acid, in facilitating Cd remediation by lesser swine cress (Coronopus didymus, Brassicaceae).

Chemically assisted phytoremediation is suggested as an effective approach to amplify the metal-remediating potential of hyperaccumulators. The current study assessed the efficiency of two biodegradable chelants (S,S-ethylenediamine disuccinic acid, EDDS; nitrilotriacetic acid, NTA) in enhancing the remediation of Cd by Coronopus didymus (Brassicaceae). C. didymus growing in Cd-contaminated soil (35-175 mg kg-1 soil) showed increased growth and biomass due to the hormesis effect, and chelant supplementation further increased growth, biomass, and Cd accumulation. A significant interaction with chelants and different Cd concentrations was observed, except for Cd content in roots and Cd content in leaves, which exhibited a non-significant interaction with chelant addition. The effect of the NTA amendment on the root dry biomass and shoot dry biomass was more pronounced than EDDS at all the Cd treatments. Upon addition of EDDS and NTA, bio-concentration factor values were enhanced by ~184-205 and ~ 199-208, respectively. The tolerance index of root and shoot increased over the control upon the addition of chelants, with NTA being better than EDDS. With chelant supplementation, bio-accumulation coefficient values were in the order Cd35 + NTA (~163%) > Cd105 + NTA (~137%) > Cd35 + EDDS (~89%) > Cd175 + NTA (~85%) > Cd105 + EDDS (~62%) > Cd175 + EDDS (~40%). The translocation factor correlated positively (r ≥ 0.8) with tolerance index and Cd accumulation in different plant parts. The study demonstrated that chelant supplementation enhanced Cd-remediation efficiency in C. didymus as depicted by improved plant growth and metal accumulation, and NTA was more effective than EDDS in reclaiming Cd.

Enhanced plasticity and reproductive fitness of floral and seed traits facilitate non-native species spread in mountain ecosystems.

Floral and seed traits, their relationships, and responses to abiotic constraints are considered the key determinants of the invasion success of non-native plant species. However, studies evaluating the pattern of floral and seed traits of non-native species in mountain ecosystems are lacking. In this study, we determined (a) whether the floral and seed traits of native and non-native species show similarity or dissimilarity across elevations in mountains, and (b) whether the non-native species follow different allometric patterns compared with native species. Functional variations between native and non-native species were assessed through floral and seed traits: flower count, flower display area, flower mass, specific flower area, seed count, and seed mass across an elevational gradient. Permanent plots (20 × 20 m) were laid at each 100 m elevation rise from 2000 to 4000 m a.s.l. for sampling of herbaceous plant species. The mean values of floral and seed traits such as flower display area, specific flower area, and seed count were significantly higher for non-native species compared to native species. A significant difference in trait values (flower display area, flower mass, seed count, and seed mass) between non-native species and native species was observed along the elevational gradient, except for flower count and specific flower area. The bivariate relationship revealed non-native species to exhibit a stronger relationship between flower display area ∼ flower mass, and flower display area ∼ seed mass traits than the native species. Non-native species showed enhanced reproductive ability under varying environmental conditions along an elevational gradient in mountain ecosystems. Greater flower display area and seed mass at lower elevations and a stronger overall trait-trait relationship among non-native species implied resource investment in pollinator visualization, flower mass, and seed quality over seed quantity. The study concludes that enhanced plasticity and reproductive fitness of floral and seed traits would consequently aid non-native species to adapt, become invasive, and displace native species in mountain ecosystems if the climatic barriers acting on non-native species are reduced with climate change.

Comparison of synthetic and organic biodegradable chelants in augmenting cadmium phytoextraction in Solanum nigrum.

This study focused to enhance the cadmium (Cd) phytoextraction efficiency in Solanum nigrum by applying four biodegradable chelants (10 mM)-ethylene glycol tetraacetic acid (EGTA), ethylenediamine disuccinate (EDDS), nitrilotriacetic acid (NTA), and citric acid (CA), when grown in Cd-spiked soil (12 and 48 mg kg-1). Plant height, dry biomass, photosynthetic traits, and metal accumulation varied significantly with Cd and chelant treatments. Cadmium-toxicity resulted in reduction of plant growth and photosynthetic physiology, whereas chelant supplementation alleviated the toxic effect of Cd and increased its accumulation. Tolerance index value increased with addition of chelants in the order: EGTA (1.57-1.63) >EDDS (1.39-1.58) >NTA (1.14-1.50) >CA (1-1.22) compared with Cd (0.46-1.08). Transfer coefficient of root increased with supplementation of EGTA (3.40-3.85), EDDS (3.10-3.40), NTA (2.60-2.90), and CA (1.85-2.29), over Cd-alone (1.61-1.63). Similarly, translocation factor was also increased upon addition of EGTA (0.52-0.73), EDDS (0.35-0.81), NTA (0.38-0.75), and CA (0.53-0.54), compared with Cd-alone (0.36-0.59). Maximum Cd removal (67.67% at Cd12 and 36.05% at Cd48) was observed with supplementation of EGTA. The study concludes that the supplementation of EGTA and EDDS with S. nigrum can be employed as an efficient and environmentally safe technique for reclamation of Cd-contaminated soils.

Apart from the selection of a good hyperaccumulator, the choice of chelant (biodegradable/non-biodegradable) is an important aspect for the successful phytoextraction of metals from contaminated soil. We reported for the first time the potential of ethylene glycol tetraacetic acid (EGTA; a biodegradable chelant) in enhancing Cd phytoextraction by Solanum nigrum. Comparative appraisal of metal extraction efficiency of biodegradable chelants at low (12 mg kg⁻¹) and high (48 mg kg⁻¹) Cd dose depicted that EGTA performed better than EDDS, NTA, and CA (other biodegradable chelants). EGTA supplementation did not induce toxicity in plants; rather it improved metal accumulation, morphology, and photosynthetic physiology.

Projected Impacts of Climate Change on the Range Expansion of the Invasive Straggler Daisy (Calyptocarpus vialis) in the Northwestern Indian Himalayan Region.

Human-induced climate change modifies plant species distribution, reorganizing ecologically suitable habitats for invasive species. In this study, we identified the environmental factors that are important for the spread of Calyptocarpus vialis, an emerging invasive weed in the northwestern Indian Himalayan Region (IHR), along with possible habitats of the weed under current climatic scenarios and potential range expansion under several representative concentration pathways (RCPs) using MaxEnt niche modeling. The prediction had a high AUC (area under the curve) value of 0.894 ± 0.010 and a remarkable correlation between the test and expected omission rates. BIO15 (precipitation seasonality; 38.8%) and BIO1 (annual mean temperature; 35.7%) had the greatest impact on the probable distribution of C. vialis, followed by elevation (11.7%) and landcover (6.3%). The findings show that, unlike the current situation, "high" and "very high" suitability areas would rise while less-suited habitats would disappear. All RCPs (2.6, 4.5, 6.0, and 8.5) indicate the expansion of C. vialis in "high" suitability areas, but RCP 4.5 predicts contraction, and RCPs 2.6, 6.0, and 8.5 predict expansion in "very high" probability areas. The current distribution of C. vialis is 21.59% of the total area of the state, with "medium" to "high" invasion suitability, but under the RCP 8.5 scenario, it might grow by 10% by 2070. The study also reveals that C. vialis may expand its niche at both lower and higher elevations. This study clarifies how bioclimatic and topographic factors affect the dispersion of invasive species in the biodiverse IHR. Policymakers and land-use managers can utilize the data to monitor C. vialis hotspots and develop scientifically sound management methods.

Biodegradable chelant-metal complexes enhance cadmium phytoextraction efficiency of Solanum americanum.

Toxic contaminants (metals and metal-containing compounds) are accumulating in the environment at an astonishing rate and jeopardize human health. Remarkable industrial revolution and the spectacular economic growth are the prime causes for the release of such toxic contaminants in the environment. Cadmium (Cd) is ranked the 7th most toxic compound by the Agency for Toxic Substances and Disease Registry (USA), owing to its high carcinogenicity and non-biodegradability even at miniscule concentration. The present study assessed the efficiency of four biodegradable chelants [nitrilotriacetic acid (NTA), ethylenediamine disuccinate (EDDS), ethylene glycol tetraacetic acid (EGTA), and citric acid (CA)] and their dose (5 mM and 10 mM) in enhancing metal accumulation in Solanum americanum Mill. (grown under 24 mg Cd kg-1 soil) through morpho-physiological and metal extraction parameters. Significant variations were observed for most of the studied parameters in response to chelants and their doses. However, ratio of root and shoot length, and plant height stress tolerance index differed non-significantly. The potential of chelants to enhance Cd removal efficiency was in the order - EGTA (7.44%) > EDDS (6.05%) > NTA (4.12%) > CA (2.75%). EGTA and EDDS exhibited dose-dependent behavior for Cd extraction with 10 mM dose being more efficient than 5 mM dose. Structural equation model (SEM) depicted strong positive interaction of metal extraction parameters with chelants (Z-value = 11.61, p = 0.001). This study provides insights into the importance of selecting appropriate dose of biodegradable chelants for Cd extraction, as high chelant concentration might also result in phytotoxicity. In the future, phytoextraction potential of these chelants needs to be examined through field studies under natural environmental conditions.

Bridging the gap: linking morpho-functional traits' plasticity with hyperaccumulation.

Plant species exhibiting heavy metal tolerance are instrumental in phytoremediation of metalliferous sites. Most of the time, variations in plant functional traits (PFTs) are overlooked while identifying hyperaccumulators. However, investigating morphological, physiological, and phenological variations can contribute to our knowledge about stress tolerance, and aid in identifying potential hyperaccumulators. In the present study, we investigated variation in morpho-functional traits in Solanum nigrum, a known hyperaccumulator, under lead (Pb) stress. Twenty-one PFTs including 9 above-ground (leaf count, leaf area, specific leaf area, leaf dry matter content, leaf thickness, leaf dry mass, shoot length, stem dry mass, stem diameter), 3 below-ground (root length, root dry mass, and root diameter), 4 reproductive (flower bud count, fruit count, flower count, and fruit dry mass), and 5 photosynthetic traits (total chlorophyll, total carotenoid, chlorophyll a, chlorophyll b, and photosynthetic efficiency) under varying Pb concentrations (500-2000 mg kg-1) were assessed. Pillai's trace test (MANOVA) depicted significant variations in above-ground, below-ground, and photosynthetic traits, whereas reproductive traits did not vary significantly with progressive metal concentration. However, most of the studied traits except flower count, fruit dry mass, and chlorophyll b varied significantly under Pb stress. The study depicts that enhanced PFT's plasticity enables S. nigrum to grow in Pb-contaminated soil effectively without impacting plant fitness. Plasticity of morpho-functional traits, therefore, establishes itself as a resourceful approach in successful identification of phytoremediation capacity of a plant.

Patterns of plant communities along vertical gradient in Dhauladhar Mountains in Lesser Himalayas in North-Western India.

Mountains are definitely the most rugged, yet frail resources and biodiversity-rich regions of the world. Environmental variables directly affect species composition, growth patterns, and the ecosystem resulting in a drastic change in the vegetation composition along ascending elevations. The present study investigated vegetation composition, nestedness, and turnover in plant communities along a vertical gradient (2000 to 4000 m) in Dhauladhar Mountains, Lesser Himalayas, India. We determined how α-diversity pattern and nestedness-related processes or turnover (ß-diversity) causes dissimilarity in plant communities' composition along the vertical gradient. Overall, 21 permanent plots (20 × 20 m2) at every 100 m interval from 2000 to 4000 m were established. A sampling of shrubs and herbaceous species was done by marking sub-plots of 5 × 5 m2 and 1 × 1 m2, respectively, within permanent plots. We observed an inverted hump-shaped pattern for evenness index (E), a unimodal hump-shaped pattern for Shannon index (H'), Margalef's richness index, and ß-Whittaker (ßw) diversity, and mild-hump-shaped pattern for Simpson index (λ) across the elevational gradient. Turnover (ßsim) and the nestedness-resultant component of ß-diversity (ßsne) significantly differed across the elevational gradient. The observed ß-diversity patterns revealed that the species replacement rate was less in the mid-altitude communities as compared to lower and higher altitude communities. It was largely attributed to the ecotonic nature of mid-altitudes, which benefited mid-elevational communities rather than low or high altitude communities. Besides lower altitudes, the increased human interference has led to disturbance and subsequent homogenization of flora across the mid-altitudes. With respect to this, the present study signifies the need for preserving the mid-altitudinal communities, without undermining the importance of conserving the low and high altitude communities.

Physio-biochemical and morphological characters of halophyte legume shrub, Acacia ampliceps seedlings in response to salt stress under greenhouse.

Acacia ampliceps (salt wattle), a leguminous shrub, has been introduced in salt-affected areas in the northeast of Thailand for the remediation of saline soils. However, the defense mechanisms underlying salt tolerance A. ampliceps are unknown. We investigated various physio-biochemical and morphological attributes of A. ampliceps in response to varying levels of salt treatment (200-600 mM NaCl). Seedlings of A. ampliceps (25 ± 2 cm in plant height) raised from seeds were treated with 200 mM (mild stress), 400 and 600 mM (extreme stress) of salt treatment (NaCl) under greenhouse conditions. Na(+) and Ca(2+) contents in the leaf tissues increased significantly under salt treatment, whereas K(+) content declined in salt-stressed plants. Free proline and soluble sugar contents in plants grown under extreme salt stress (600 mM NaCl) for 9 days significantly increased by 28.7 (53.33 µmol g(-1) FW) and 3.2 (42.11 mg g(-1) DW) folds, respectively over the control, thereby playing a major role as osmotic adjustment. Na(+) enrichment in the phyllode tissues of salt-stressed seedlings positively related to total chlorophyll (TC) degradation (R (2) = 0.72). Photosynthetic pigments and chlorophyll fluorescence in salt-stressed plants increased under mild salt stress (200 mM NaCl). However, these declined under high levels of salinity (400-600 mM NaCl), consequently resulting in a reduced net photosynthetic rate (R (2) = 0.81) and plant dry weight (R (2) = 0.91). The study concludes that A. ampliceps has an osmotic adjustment and Na(+) compartmentation as effective salt defense mechanisms, and thus it could be an excellent species to grow in salt-affected soils.

Too much is bad--an appraisal of phytotoxicity of elevated plant-beneficial heavy metal ions.

Heavy metal ions such as cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) are considered essential/beneficial for optimal plant growth, development, and productivity. However, these ions readily impact functions of many enzymes and proteins, halt metabolism, and exhibit phytotoxicity at supra-optimum supply. Nevertheless, the concentrations of these heavy metal ions are increasing in agricultural soils worldwide via both natural and anthropogenic sources that need immediate attention. Considering recent breakthroughs on Co, Cu, Fe, Mn, Mo, Ni, and Zn in soil-plant system, the present paper: (a) overviews the status in soils and their uptake, transport, and significance in plants; (b) critically discusses their elevated level-mediated toxicity to both plant growth/development and cell/genome; (c) briefly cross talks on the significance of potential interactions between previous plant-beneficial heavy metal ions in plants; and (d) highlights so far unexplored aspects in the current context.

Characterization and antioxidant activity of essential oils from fresh and decaying leaves of Eucalyptus tereticornis.

The composition of essential oils hydrodistilled from fresh and decaying leaves of Eucalyptus tereticornis was analyzed by means of gas chromatography and mass spectrometry, and a total of 68 constituents were identified. The essential oils were assayed for antioxidant activity in terms of scavenging of 2,2-diphenyl-1-picrylhydrazil (DPPH) and hydroxyl (OH(*)) radical, and superoxide anion (O2(-*)).The major constituents of the fresh leaf oil were alpha-pinene (28.53%) and 1,8-cineole (19.48%), whereas in the decaying leaf oil, beta-citronellal (14.15%), (-)-isopulegol (13.35%), and (+)-beta-citronellol (10.73%) were the major components. Both essential oils exhibited a strong radical scavenging activity against DPPH radical with IC50 values of 110 and 139.8 microg/mL for fresh and decaying leaf oil, respectively (IC50 of BHT = 164.2 microg/mL). Further, the essential oils (at 400 microg/mL) also exhibited OH(*) (56-62%) and O2(-*) (65-69%) scavenging activity parallel to the commercial antioxidant BHT/ascorbic acid. However, unlike the essential oils, the major monoterpene constituents exhibited significantly less scavenging activity (<35% DPPH or OH(*); at 400 microg/mL). The study concluded that fresh and decaying leaves of E. tereticornis are a source of monoterpenoid rich oil exhibiting antioxidant activity.

Nitric oxide alleviates arsenic toxicity by reducing oxidative damage in the roots of Oryza sativa (rice).

Nitric oxide (NO) is a bioactive gaseous, multifunctional molecule playing a central role and mediating a variety of physiological processes and responses to biotic and abiotic stresses including heavy metals. The present study investigated whether NO applied exogenously as sodium nitroprusside (SNP) has any protective role against arsenic (As) toxicity in Oryza sativa (rice). Treatment with 50 microM SNP (a NO donor) significantly ameliorated the As-induced (25 or 50 microM) decrease in root and coleoptile length of rice. Further, As-induced oxidative stress measured in terms of malondialdehyde (MDA), superoxide ion (O(2)(-)), root oxidizability and H2O2 content was lesser upon supplementation of NO. It indicated a reactive oxygen species (ROS) scavenging activity of NO. NO addition reversed (only partially) the As-induced increase in activities of antioxidant enzymes - superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase. The study concludes that exogenous NO provides resistance to rice against As-toxicity and has an ameliorating effect against As-induced stress.

Effect of 2-benzoxazolinone (BOA) on seedling growth and associated biochemical changes in mung bean (Phaseolus aureus).

BOA (2-benzoxazolinone) is a potent phytotoxin present in several graminaceous crops such as rye, maize and wheat. Due to its wide range of phytotoxicity, it is considered as a potential pesticide. A study was conducted to explore the impact of BOA on the radicle and plumule elongation of mung bean (Phaseolus aureus) and associated changes in the macromolecular content - proteins and carbohydrates - and activities of enzymes like amylases, proteases, polyphenol oxidases and peroxidases. BOA significantly reduced the radicle and plumule length of P. aureus, and the contents of proteins and carbohydrates in both root and leaf tissue. On the other hand, activities of hydrolytic enzymes - proteases, amylases, polyphenol oxidases and peroxidases - increased substantially in both root and leaf tissue of P. aureus upon BOA exposure. This indicated that BOA treatment induced stress in P. aureus and enhanced enzyme activities to counter the induced stress and continue the growth. In other words, BOA-induced stress altered the plant biochemical status and related enzyme activities resulting in increased metabolism that serves to provide protection against cellular injury. Such studies providing information about the biomolecular content and enzymatic activities in response to natural products serve as clues for furtherance of knowledge about the modes of action of natural compounds of commercial interest.

alpha-Pinene inhibits growth and induces oxidative stress in roots.

BACKGROUND AND AIMS: Determining the mode of action of allelochemicals is one of the challenging aspects in allelopathic studies. Recently, allelochemicals have been proposed to cause oxidative stress in target tissue and induce an antioxidant mechanism. alpha-Pinene, one of the common monoterpenoids emitted from several aromatic plants including forest trees, is known for its growth-inhibitory activity. However, its mechanism of action remains unexplored. The aim of the present study was to determine the inhibitory effect of alpha-pinene on root growth and generation of reactive oxygen species, as indicators of oxidative stress and changes in activities of antioxidant enzymes. METHODS: Effects of alpha-pinene on early root growth were studied in five test species, Cassia occidentalis, Amaranthus viridis, Triticum aestivum, Pisum sativum and Cicer arietinum. Electrolyte leakage, lipid peroxidation, hydrogen peroxide generation, proline accumulation, and activities of the enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT) and glutathione reductase (GR) were studied in roots of C. occidentalis. KEY RESULTS: alpha-Pinene inhibited the radicle growth of all the test species. Exposure of C. occidentalis roots to alpha-pinene enhanced solute leakage, and increased levels of malondialdehyde, proline and hydrogen peroxide, indicating lipid peroxidation and induction of oxidative stress. Activities of the antioxidant enzymes SOD, CAT, GPX, APX and GR were significantly elevated, thereby indicating the enhanced generation of reactive oxygen species (ROS) upon alpha-pinene exposure. Increased levels of scavenging enzymes indicates their induction as a secondary defence mechanism in response to alpha-pinene. CONCLUSIONS: It is concluded that alpha-pinene inhibits early root growth and causes oxidative damage in root tissue through enhanced generation of ROS, as indicated by increased lipid peroxidation, disruption of membrane integrity and elevated antioxidant enzyme levels.

Chemical composition and phytotoxicity of volatile essential oil from intact and fallen leaves of Eucalyptus citriodora.

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.

Effect of parthenin--a sesquiterpene lactone from Parthenium hysterophorus--on early growth and physiology of Ageratum conyzoides.

A study was undertaken to assess the effect of parthenin--a sesquiterpene lactone from Parthenium hysterophorus--on the germination, growth, and some associated physiological changes in Ageratum conyzoides. The study reveals that germination and growth of A. conyzoides was severely reduced by parthenin in the concentration range of 50, 100, and 200 microM, while at 400 microM a complete inhibition of germination was observed. The radicle length of A. conyzoides was reduced more than the plumule length. Further, the content of the photosynthetic pigment chlorophyll was appreciably reduced in the leaves of test plants spray treated with parthenin at 200 microM concentration. However, this inhibitory effect declined with the passage of time and at 10 days after treatment only a 25% reduction in chlorophyll content was observed compared to 76% on the first day after spray. Likewise, the cellular respiration measured through 2,3,5-triphenyl tetrazolium chloride was found to be less in the treated leaves, and the inhibitory response also declined with time. The content of proteins and carbohydrates decreased with the passage of time after parthenin treatment. The specific activities of the enzymes protease and alpha- and beta-amylase were also adversely affected in the parthenin treated leaves. In the case of protease. the activity decreased with passage of time while those of the amylases increased. Thus, we conclude that parthenin affects the germination and growth of A. conyzoides by altering the contents of some macromolecules and the specific activities of some enzymes. Such observations may be helpful in further exploring parthenin's mode of action.