Comparative analysis of soil quality and enzymatic activities under different tillage based nutrient management practices in soybean-wheat cropping sequence in Vertisols.

In the modern era, intensive agricultural practices such as agrochemicals are applied in excessive amounts to enhance agricultural production. However, imbalanced adoption of these chemicals has arisen in the dwindling of agriculture factor productivity and soil quality. To maintain soil fertility and production, these chemical fertilizers must be supplemented with organic inputs. Keeping this in the backdrop, a research trail was established during 2018-19 and 2019-20 years at Research Farm of Agriculture University, Kota, India. The treatment setup was comprised of 5 treatment modules viz., conservation tillage + organic management (CAOM), conservation tillage + chemical management (CACM), conventional tillage + chemical management (CTCM), conventional tillage + organic management (CTOM) and the package of practices (PoPs) with four replications. Results indicated that the highest organic carbon (0.68%), bacterial (29.11 × 107 cfu g-1), fungal (4.77 × 104 cfu g-1), actinomycetes populations (5.67 × 104 cfu g-1), acid phosphatase (44.1 µg g-1 h-1), urease (45.3 µg g-1 h-1) and dehydrogenase (23.3 µg triphenylformazan [TPF] g-1 h-1) activity in soil were found in the treatment of conservation organic system during both the years of study at each soil depth. In contrast to other parameters, the highest system productivity was observed with conservation chemical crop management approaches, with a soybean equivalent yield of 4615 kg ha-1 in a soybean-wheat system of production. Furthermore, the soil quality index (SQI) significantly varied from the lowest score (0.30) at 45-60 cm layer of soil in the package of practices to the highest score (0.92) at 0-15 cm layer of soil with regards to the conservation organic which shows, 206.67 percent enhancement through the soil profile of various crop management practices. The SQI variation from 0-15 to 45-60 cm soil depth was 130.0, 81.08, 60.0, 175.0 and 83.33 percent, respectively, for CAOM, CACM, CTCM, CTOM and PoPs. Amongst, different systems, the highest mean performance was noticed under the conservation organic systems for physical and biological properties. Hence, in line with the salient outcome, we may propose that the conservation chemical system needs to be followed to improve crop productivity, whereas, conservation organic seems a good option for soil health with long-term viability.

Diagnostic Dilemma of Central Nervous System Tuberculosis with Neurocysticercosis and Neurosarcoidosis: A Case Report.

Multiple ring-enhancing lesions are commonly encountered abnormalities in neuroimaging. There are many differentials for such lesions as infections, neoplasms, vascular lesions, inflammatory and demyelinating conditions, and granulomatous diseases. In developing countries, tuberculoma and neurocysticercosis are the two important etiologies to be considered. This case report illustrates how multiple ring-enhancing lesions can lead to our management in one direction while the true diagnosis remains elusive. A 53-year-old male who presented with a headache was initially diagnosed and treated as neurocysticercosis, then neurosarcoidosis ultimately turned out to be a case of Central Nervous System Tuberculosis on further evaluation. Consideration of only clinical scenarios and neurological imaging can lead to diagnostic inaccuracy, mismanagement and poor outcome, therefore, other supporting lab investigations should be considered for making a correct diagnosis. Keywords: brain; case reports; neurocysticercosis; sarcoidosis; tuberculoma.

Implementation of nutrition and physical activity-related policies and practices on college campuses participating in the Healthier Campus initiative.

Objective: To evaluate implementation of nutrition/physical activity-related policies/practices at colleges participating in a healthy campus initiative and campus health leaders' perceptions of policies/practices' support for student health and ease of/barriers to implementation. Participants: Health leaders at colleges participating in the Healthier Campus Initiative (HCI), with completed or ongoing three-year HCI commitments. Methods: Surveys asked which of 41 guidelines were implemented and perceptions around support for student health and ease of/barriers to implementation. Qualitative interviews explored similar domains. Results: Campuses with completed HCI commitments (n = 17) averaged 27.6 guidelines implemented, versus 21.1 on campuses with commitments ongoing (n = 13; p = 0.003). Perceived support for student health and implementation ease varied by guideline. Common implementation barriers included financial costs and time. Interviews largely reinforced these findings. Conclusions: Completion of a campus environmental change initiative may be associated with more health-supporting practices. Campuses may benefit from implementing coordinated policy/practice changes supporting healthy eating and physical activity.

Physio-biochemical responses of wheat plant towards salicylic acid-chitosan nanoparticles.

Sustained source-activity is imperative for vigor plant growth and yield. In present study, physio-biochemical responses of wheat plant contributing to source-activity were measured after application of salicylic acid-chitosan nanoparticles (SA-CS NPs). SA-CS NPs slowly release SA for sustained availability to plant. In seedling bioassay, as compared with salicylic acid (SA), SA-CS NPs incurred up to ~1.5 folds increased activities of seed reserve food remobilizing enzymes for substantial mobilization of reserve food to growing seedlings and enhanced seedling vigor index (SVI) by 1.6 folds. At booting stage, foliar application of SA-CS NPs (0.01-0.08%; w/v) enhanced the activities of superoxide dismutase (1.94 folds), catalase (1.33 folds), peroxidase (1.99 folds) and polyphenol oxidase (1.04 folds) in flag leaf. SA-CS NPs further contrived cellular homeostasis by comforting reactive oxygen species (ROS), malondialdehyde (MDA) and proline contents in flag leaf. SA-CS NPs (0.08%; w/v) significantly increased chlorophylls (a-b) contents (1.46 folds), spike length without awns, spike lets per spike and grain weight per pot as compared with SA. Study categorically explicates that slow release of SA from SA-CS NPs could exert significant effect on source-activity by maneuvering various physio-biochemical responses of wheat plant.

Emerging Trends in Metalloid-Dependent Signaling in Plants.

Metalloids are semiconducting elements that constitute a small group in the periodic table of elements. Their occurrence in nature either poses an environmental threat or benefit to plants. The precise mechanisms or manner of crosstalk of metalloid interference and sensing remain open questions. Standard plant nutrient solutions contain the metalloid boron (B) as a micronutrient, while silicon (Si) is considered a beneficial element routinely supplied only to some plants such as grasses. By contrast, arsenic (As) is a severe environmental hazard to most organisms, including plants, while the less abundant metalloids germanium (Ge), antimony (Sb), and tellurium (Te) display variable degrees of toxicity. Here we review the molecular events and mechanisms that could explain the contrasting (or overlapping) action of metalloids on the cell and cell signaling.

College campuses' influence on student weight and related behaviours: A review of observational and intervention research.

Research indicates that most college students are not meeting dietary and physical activity guidelines, and the average student gains an estimated 1.6-3.0 kg during 4 years of study. College administrations are well-positioned to influence student weight-related health behaviours by ensuring that campus environments/policies promote health. However, to date, campus health interventions have largely addressed individual and interpersonal factors rather than environmental/policy-level changes. Using an ecological perspective, this narrative review synthesizes the literature on campus environmental/policy-level factors (e.g., food availability, physical activity requirements) associated with student diet, physical activity and weight, as well as campus interventions to address these factors. Web of Science and PubMed databases were searched between December 2018 and November 2019. Results indicate that campus food environments may contribute to overconsumption and weight gain, and the number of campuses requiring students to participate in physical activity courses is in decline. Eight examples of environmental/policy-level campus interventions are presented: nutrition labels in dining halls, campus-wide healthy choice marketing campaigns, restricted payment methods for à la cart dining, trayless dining, health-themed residence halls, peer health education programmes, active classroom spaces and physical activity course requirements. Implications for research and health promotion programmes/policies in the field of college health are discussed.

Remodeling of Root Growth Under Combined Arsenic and Hypoxia Stress Is Linked to Nutrient Deprivation.

Root architecture responds to environmental stress. Stress-induced metabolic and nutritional changes affect the endogenous root development program. Transcriptional and translational changes realize the switch between stem cell proliferation and cell differentiation, lateral root or root hair formation and root functionality for stress acclimation. The current work explores the effects of stress combination of arsenic toxicity (As) and hypoxia (Hpx) on root development in Arabidopsis thaliana. As revealed previously, combined As and Hpx treatment leads to severe nutritional disorder evident from deregulation of root transcriptome and plant mineral contents. Both As and Hpx were identified to pose stress-specific constraints on root development that lead to unique root growth phenotype under their combination. Besides inhibition of root apical meristem (RAM) activity under all stresses, As induced lateral root growth while root hair density and lengths were strongly increased by Hpx and HpxAs-treatments. A dual stimulation of phosphate (Pi)-starvation response was observed for HpxAs-treated plant roots; however, the response under HpxAs aligned more with Hpx than As. Transcriptional evidence along with biochemical data suggests involvement of PHOSPHATE STARVATION RESPONSE 1; PHR1-dependent systemic signaling. Pi metabolism-related transcripts in close association with cellular iron homeostasis modulate root development under HpxAs. Early redox potential changes in meristematic cells, differential ROS accumulation in root hair zone cell layers and strong deregulation of NADPH oxidases, NADPH-dependent oxidoreductases and peroxidases signify a role of redox and ROS signaling in root architecture remodeling under HpxAs. Differential aquaporin expression suggests transmembrane ROS transport to regulate root hair induction and growth. Reorganization of energy metabolism through NO-dependent alternate oxidase, lactate fermentation, and phosphofructokinase seems crucial under HpxAs. TOR and SnRK-signaling network components were potentially involved in control of sustainable utilization of available energy reserves for root hair growth under combined stress as well as recovery on reaeration. Findings are discussed in context of combined stress-induced signaling in regulation of root development in contrast to As and Hpx alone.

Interference between arsenic-induced toxicity and hypoxia.

Plants often face combinatorial stresses in their natural environment. Here, arsenic (As) toxicity was combined with hypoxia (Hpx) in the roots of Arabidopsis thaliana as it often occurs in nature. Arsenic inhibited growth of both roots and leaves, whereas root growth almost entirely ceased in Hpx. Growth efficiently resumed, and Hpx marker transcripts decreased upon reaeration. Compromised recovery from HpxAs treatment following reaeration indicated some persistent effects of combined stresses despite lower As accumulation. Root glutathione redox potential turned more oxidized in Hpx and most strongly in HpxAs. The more oxidizing root cell redox potential and the lowered glutathione amounts may be conducive to the growth arrest of plants exposed to HpxAs. The stresses elicited changes in elemental and transcriptomic composition. Thus, calcium, magnesium, and phosphorous amounts decreased in rosettes, but the strongest decline was seen for potassium. The reorganized potassium-related transcriptome supports the conclusion that disturbed potassium homeostasis contributes to the growth phenotype. In a converse manner, photosynthesis-related parameters were hardly affected, whereas accumulated carbohydrates under all stresses and anthocyanins under Hpx exclude carbohydrate limitation. The study demonstrates the existence of both synergistic since mutually aggravating effects and antagonistic effects of single and combined stresses.

Dissemination of healthy kids out of school principles for obesity prevention: A RE-AIM analysis.

Health-promoting behaviors for childhood obesity prevention are needed across multiple environments where children spend time, including out-of-school time (OST). Therefore Healthy Kids Out of School (HKOS) developed intervention strategies to promote three evidence-based principles (Drink Right, Move More, Snack Smart) for obesity prevention in OST. The strategies were developed with stakeholder input, disseminated, and evaluated (2012-2015) in two volunteer-led OST organizations, Boy Scouts of America (BSA) and 4-H, across three US states using the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework. Mixed methods were used involving surveys, key informant interviews, and organizational-level data collection. Sixty out of 81 (74.1%) BSA districts and 4-H counties reaching 84,590 children (72% of children participating in BSA and 4-H in three states) adopted the strategies. 530 surveys completed by local OST leaders at baseline and 294 at follow-up showed the percentage of programs offering healthy beverages and opportunities for physical activity increased from baseline to follow-up (beverages 26% baseline, 35% follow-up, odds ratio (OR) 1.53; physical activity 31% baseline, 45% follow-up, OR 1.79; all p < 0.05). The increasing trend for healthy snacks was statistically non-significant (p = 0.09). Leaders interviewed reported the strategies were easy to implement, a good fit with their program, facilitated success, and they expected to maintain the changes. Integration of HKOS customized materials (BSA patch and 4-H pin) on BSA and 4-H national websites is a broader indicator of maintenance. Intervention strategies developed with stakeholder input and disseminated with training can effectively facilitate healthy environments for children, and have potential for national scale.

Evaluation of Let's Move! active schools activation grants.

Let's Move! Active Schools (LMAS), now Active Schools, is a national initiative in the United States (US) that aims to engage schools to increase students' opportunities to be physically active. This evaluation describes changes in school-level practices related to physical education (PE) and physical activity (PA) among schools that received an LMAS-partner grant from ChildObesity180 or Fuel Up to Play 60 (FUTP60). ChildObesity180 and FUTP60 asked grantee schools to complete nine common questions, between October 2013 and August 2014, before and after receiving the grants to assess progress in implementing practices for PE and PA. "Yes" responses indicated presence of PE/PA-supportive practices. For schools with complete pre and post data (n=972), frequencies of "yes" responses were calculated for each practice at pre/post. Schools receiving a FUTP60 partner grant reported statistically significant improvements from pre to post across five practices for PE and PA, and ChildObesity180 grantees reported significant increases on all practices except daily recess, which was already in place at 95% of schools at pre-survey. Schools across both grant programs reported the largest increases for promoting PA via messaging, implementing classroom PA breaks, and providing PA before and after school. Schools in both programs reported smaller, but statistically significant, increases in requiring the recommended minutes of PE. This study illustrates the feasibility of offering small grants, at a national scale, for schools to make changes that support PA throughout the day. Results suggest that schools can shift PA policies and practices over the course of a school year.

Low parental awareness about energy (calorie) recommendations for children's restaurant meals: findings from a national survey in the USA.

OBJECTIVE: To assess parental awareness of per-meal energy (calorie) recommendations for children's restaurant meals and to explore whether calorie awareness was associated with parental sociodemographic characteristics and frequency of eating restaurant food. DESIGN: Cross-sectional online survey administered in July 2014. Parents estimated calories (i.e. kilocalories; 1 kcal=4·184 kJ) recommended for a child's lunch/dinner restaurant meal (range: 0-2000 kcal). Responses were categorized as 'underestimate' (600 kcal). Confidence in response was measured on a 4-point scale from 'very unsure' to 'very sure'. Logistic regressions estimated the odds of an 'accurate' response and confident response ('somewhat' or 'very sure') by parental sociodemographic characteristics and frequency of eating from restaurants. Sampling weights based on demographics were incorporated in all analyses. SETTING: USA. SUBJECTS: Parents (n 1207) of 5-12-year-old children. RESULTS: On average, parents estimated 631 (se 19·4) kcal as the appropriate amount for a 5-12-year-old child's meal. Thirty-five per cent answered in the accurate range, while 33·3 and 31·8 % underestimated and overestimated, respectively. Frequent dining at restaurants, lower income and urban geography were associated with lower odds of answering accurately. Parents' confidence in their estimates was low across the sample (26·0 % confident) and only 10·1 % were both accurate and confident. CONCLUSIONS: Parent education about calorie recommendations for children could improve understanding and use of menu labelling information in restaurants. Targeted strategies are recommended to ensure that such efforts address, rather than exacerbate, health disparities.

A pilot and feasibility study to assess children's consumption in quick-service restaurants using plate waste methodology.

BACKGROUND: Children regularly consume foods from quick-service restaurants (QSR), but little is known about the foods that children order, the calories and nutrients consumed, the accuracy of stated calorie information, or the ability to assess food orders and consumption in QSRs. This study evaluated the feasibility of plate waste collection in QSRs and examined children's orders and consumption of meals from the standard and children's menus. Additional aims were to examine if the meals ordered met healthier standards for children's menu items and determine the accuracy of the QSR-stated energy content of foods. METHODS: Fifteen QSRs, two malls, and 116 eligible parents were approached to participate in the study in 2015. Among the families recruited, children's meal orders and consumption were analyzed using plate waste methodology, and a subsample of foods was analyzed using bomb calorimetry in 2015. RESULTS: Two individual QSRs and one mall food court with two QSRs agreed to participate, and n = 50 participants (parents with children between the ages of 5-10 years) were recruited. Children consumed on average 519 calories, 5.7 g saturated fat, 957 mg sodium, 3.7 g fiber, and 22.7 g sugar. Children ordered and consumed significantly fewer calories and less sodium and sugar with meals ordered exclusively from the children's menu compared with the standard menu. Overall there were no significant differences between the measured and stated energy contents of the QSR foods. CONCLUSIONS: Conducting plate waste research in QSRs is feasible and there is concordance with stated calorie information. Consuming foods exclusively from the children's menu may help limit overconsumption in QSRs.

Cadmium-induced changes in vacuolar aspects of Arabidopsis thaliana.

We have examined the changes due to Cd treatment in the vacuolar form in root tip cortical cells in Arabidopsis thaliana employing a transformant with GFP fused to a tonoplast protein. A Cd-induced enhancement in complexity with general expansion of vacuolar system within 24 h was evident. The changes in the vacuolar form were dependent on the applied Cd concentrations. Concomitantly, as revealed through dithizone staining, Cd accumulated in the seedling roots exhibiting abundance of Cd-dithizone complexes in root tip, root hairs and vasculature. To get insight into the involvement of SNARE protein-mediated vesicle fusion in Cd detoxification, the magnitude of Cd toxicity in a couple of knock out mutants of the vacuolar Qa-SNARE protein VAM3/SYP22 was compared with that in the wild type. The Cd toxicity appeared to be comparable in the mutants and the wild type. In order to analyze the Cd effects at cellular level, we treated the Arabidopsis suspension-cultured cells with Cd. Cd, however, did not induce a change in the vacuolar form in suspension-cultured cells although Cd measured with ICP-MS was obviously taken up into the cell. The V-ATPase activity in the microsomal fractions from vacuoles isolated from A. thaliana suspension cultured cells remained unaffected by Cd. Changes in the levels of certain metabolites of Cd-treated cells were also not so distinct except for those of glutathione. The significance of findings is discussed.

Vacuolar compartmentalization as indispensable component of heavy metal detoxification in plants.

Plant cells orchestrate an array of molecular mechanisms for maintaining plasmatic concentrations of essential heavy metal (HM) ions, for example, iron, zinc and copper, within the optimal functional range. In parallel, concentrations of non-essential HMs and metalloids, for example, cadmium, mercury and arsenic, should be kept below their toxicity threshold levels. Vacuolar compartmentalization is central to HM homeostasis. It depends on two vacuolar pumps (V-ATPase and V-PPase) and a set of tonoplast transporters, which are directly driven by proton motive force, and primary ATP-dependent pumps. While HM non-hyperaccumulator plants largely sequester toxic HMs in root vacuoles, HM hyperaccumulators usually sequester them in leaf cell vacuoles following efficient long-distance translocation. The distinct strategies evolved as a consequence of organ-specific differences particularly in vacuolar transporters and in addition to distinct features in long-distance transport. Recent molecular and functional characterization of tonoplast HM transporters has advanced our understanding of their contribution to HM homeostasis, tolerance and hyperaccumulation. Another important part of the dynamic vacuolar sequestration syndrome involves enhanced vacuolation. It involves vesicular trafficking in HM detoxification. The present review provides an updated account of molecular aspects that contribute to the vacuolar compartmentalization of HMs.

Characterization of seed germination, seedling growth, and associated metabolic responses of Brassica juncea L. cultivars to elevated nickel concentrations.

Seed germination and seedling growth responses of three Brassica juncea L. cultivars, namely Varuna, Kranti, and Pusa Jai Kisan, to nickel have been characterized. Ni suppressed the seed germination differentially, suppression being greater in cv. Kranti than in others. On the basis of seedling growth performance, cv. Varuna proved most tolerant to Ni. The Ni accumulation in seedlings differed strongly among the three cultivars. The lowest and highest Ni contents were observed in the seedlings of cvs. Kranti and Pusa Jai Kisan, respectively. Despite substantial Ni accumulation, cv. Varuna was most tolerant to Ni. Ni accumulation in seedlings was accompanied by differentially altered Fe and K contents and increased levels of non-protein thiols and free proline. The O2- and H2O2 contents and their respective scavenging enzymes in the seedlings responded differentially to the Ni treatment suggesting the involvement of redox imbalance in the development of Ni toxicity. Interestingly, the greater Ni tolerance of cv. Varuna coincided with the elevated constitutive activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX). The data have implications for seedling establishment under Ni-rich conditions and in turn for phytoremediation.

Parent perspectives on nutrition and physical activity during out-of-school time.

OBJECTIVE: Out-of-school time (OST) programs serve a large, diverse population of children, including those at increased obesity risk. In this study, parents' perspectives about nutrition and physical activity (PA) during OST were assessed. DESIGN: Survey. SETTING: Online. PARTICIPANTS: Six hundred parents with a school-aged child participating in programs from selected OST organizations. MAIN OUTCOME MEASURES: Parent perspectives about the importance and availability of different foods, beverages, and PA opportunities during OST, and OST program and parent involvement in promoting healthful environments. ANALYSIS: Frequencies were used to describe parents' perspectives. Wilcoxon tests and logistic regression analyses were conducted to test for significant differences. RESULTS: Most parents reported that it was important that their children have water (96.2%), fresh fruits and vegetables (79.0%), and PA (97.2%) during OST; fewer parents reported that these were regularly available. About two thirds of parents agreed that OST programs should promote healthy environments for children, whereas one third agreed that parents alone should be responsible for children's nutrition and PA. CONCLUSIONS AND IMPLICATIONS: Results suggest that many parents would support efforts to improve OST nutrition and PA. Yet, there is a need to further understand the perceptions and motivations of different subgroups to enact successful obesity prevention efforts during OST.

Children's perceptions of weight, obesity, nutrition, physical activity and related health and socio-behavioural factors.

OBJECTIVE: Approximately one-third of children in the USA are either overweight or obese. Understanding the perceptions of children is an important factor in reversing this trend. DESIGN: An online survey was conducted with children to capture their perceptions of weight, overweight, nutrition, physical activity and related socio-behavioural factors. SETTING: Within the USA. SUBJECTS: US children (n 1224) aged 8-18 years. RESULTS: Twenty-seven per cent of children reported being overweight; 47·1% of children overestimated the rate of overweight/obesity among US children. A higher percentage of self-classified overweight children (81·9%) worried about weight than did self-classified under/normal weight children (31·1%). Most children (91·1%) felt that it was important to not be overweight, for both health-related and social-related reasons. The majority of children believed that if someone their age is overweight they will likely be overweight in adulthood (93·1%); get an illness such as diabetes or heart disease in adulthood (90·2%); not be able to play sports well (84·5%); and be teased or made fun of in school (87·8%). Children focused more on food/drink than physical activity as reasons for overweight at their age. Self-classified overweight children were more likely to have spoken with someone about their weight over the last year than self-classified under/normal weight children. CONCLUSIONS: Children demonstrated good understanding of issues regarding weight, overweight, nutrition, physical activity and related socio-behavioural factors. Their perceptions are important and can be helpful in crafting solutions that will resonate with children.

Healthy kids out of school: using mixed methods to develop principles for promoting healthy eating and physical activity in out-of-school settings in the United States.

INTRODUCTION: Widespread practices supporting availability of healthful foods, beverages, and physical activity in out-of-school-time (OST) settings would further obesity prevention efforts. The objective of this article was to describe principles to guide policy development in support of healthy eating and physical activity practices in out-of-school settings to promote obesity prevention. METHODS: The Institute of Medicine's L.E.A.D. framework (Locate Evidence, Evaluate it, Assemble it, and Inform Decisions) was used to identify practices relevant to children's healthful eating in most OST settings: 1) locate and evaluate information from a national survey of children's perceptions of healthful-food access; published research, reports, policies and guidelines; and roundtables with OST organizations' administrators; 2) assemble information to prioritize actionable practices; and 3) inform programmatic direction. RESULTS: Three evidence-informed guiding principles for short-duration OST resulted: 1) drink right: choose water instead of sugar-sweetened beverages; 2) move more: boost movement and physical activity in all programs; and 3) snack smart: fuel up on fruits and vegetables. CONCLUSION: Healthy Kids Out of School was launched to support the dissemination and implementation of these guiding principles in short-duration OST settings, complementing efforts in other OST settings to shift norms around eating and physical activity.

The relationship between metal toxicity and cellular redox imbalance.

The relationship between cellular redox imbalances leading to oxidative stress and metal toxicity in plants has been studied intensely over the past decades. This interdependency was often considered to reflect a rather indirect metal effect of cellular disregulation and progressive secondary damage development. By contrast, recent experiments revealed a clear relationship between metal stress and redox homeostasis and antioxidant capacity. Analysis of plants expressing targeted modifications of components of the antioxidant system, the comparison of closely related plant species with different degrees of toxic metal sensitivity and effector studies with, for instance, salicylic acid have established a link between the degree of plant tolerance to metals and the level of antioxidants.

The significance of amino acids and amino acid-derived molecules in plant responses and adaptation to heavy metal stress.

Plants exposed to heavy metals accumulate an array of metabolites, some to high millimolar concentrations. This review deals with N-containing metabolites frequently preferentially synthesized under heavy metal stress such as Cd, Cu, Ni, and Zn. Special focus is given to proline, but certain other amino acids and oligopeptides, as well as betaine, polyamines, and nicotianamine are also addressed. Particularly for proline a large body of data suggests significant beneficial functions under metal stress. In general, the molecules have three major functions, namely metal binding, antioxidant defence, and signalling. Strong correlative and mechanistic experimental evidence, including work with transgenic plants and algae, has been provided that indicates the involvement of metal-induced proline in metal stress defence. Histidine, other amino acids and particularly phytochelatins and glutathione play a role in metal binding, while polyamines function as signalling molecules and antioxidants. Their accumulation needs to be considered as active response and not as consequence of metabolic dys-regulation.