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Copyright of Tropical Grasslands / Forrajes Tropicales is the property of International Centre for Tropical Agriculture - CIAT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista CIENCIA UNEMI is the property of Universidad Estatal de Milagro (UNEMI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Agricultural Sciences / Revista Brasileira de Ciências Agrárias is the property of Universidade Federal Rural de Pernambuco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aluminum (Al) toxicity and phosphorus (P) deficiency are widely recognized as major constraints to agricultural productivity in acidic soils. Under this scenario, the development of ryegrass plants with enhanced P use efficiency and Al resistance is a promising approach by which to maintain pasture production. In this study, we assessed the contribution of growth traits, P efficiency, organic acid anion (OA) exudation, and the expression of Al-responsive genes in improving tolerance to concurrent low-P and Al stress in ryegrass (Lolium perenne L.). Ryegrass plants were hydroponically grown under optimal (0.1 mM) or low-P (0.01 mM) conditions for 21 days, and further supplied with Al (0 and 0.2 mM) for 3 h, 24 h and 7 days. Accordingly, higher Al accumulation in the roots and lower Al translocation to the shoots were found in ryegrass exposed to both stresses. Aluminum toxicity and P limitation did not change the OA exudation pattern exhibited by roots. However, an improvement in the root growth traits and P accumulation was found, suggesting an enhancement in Al tolerance and P efficiency under combined Al and low-P stress. Al-responsive genes were highly upregulated by Al stress and P limitation, and also closely related to P utilization efficiency. Overall, our results provide evidence of the specific strategies used by ryegrass to co-adapt to multiple stresses in acid soils. [ABSTRACT FROM AUTHOR]

With Eucalyptus urophylla x E. grandis DH3229 seedlings as test material, a experiment was conducted to study nitric oxide (NO) alleviate the toxic effects of Aluminum (A1). In this experiment, E. urophylla x E. grandis DH3229 were subjected to six treatments [ two levels of A1 stress and three levels of sodium nitroprusside (SNP) ]. In this paper, we measured four plant growth indexs (root biomass, stem biomass, leaf biomass, and root stem ratio) and nine plant physiologic indexs (chlorophyll a, clilorophyll b, chlorophyll a+b, chlorophyll a/b, MDA content, relative e-lectrical conductivity, free proline content, soluble sugar content, and SOD content) among different treatments. We used one-way ANOVAs and Duncan multiple-range test to exam the differences between four plant growth indexs and nine plant physiologic indexs in six treatments. And then, we used principle conponent analysis (PCA) to reduce the number of dimensions without much loss of information based on similarities and differences, and we defined a limited number of uprincipal componentsthat describe independent variation structures in the data. At last, we chose an appropriate SNP content to alleviate the toxic effects of Al. The results showed that A1 stress significantly inhibited root, stem, leaf biomass of seedlings, and the content of leaf chlorophyll a, chlorophyll a+b. Meanwhile, A1 stress significantly increased the relative electrical conductivity, MDA, SOD and proline content. The application of 10 µmol • L-1 SNP increased siginificantly root and leaf biomass, the content of chlorophyll a and chlorophyll b, chlorophyll a/b under A1 stress； and decreased siginificantly the relative electrical conductivity, MDA and proline content. Apply an appropriate amount of SNP could effectively alleviate the toxic effects of Al on Eucalyptus seedling growth. However, high concentration of SNP could inhibit the growth of Eucalyptus seedling. [ABSTRACT FROM AUTHOR]

Low phosphate (Pi) availability and high aluminum (Al) toxicity constitute two major plant mineral nutritional stressors that limit plant productivity on acidic soils. Advances toward the identification of genes and signaling networks that are involved in both stresses in model plants such as Arabidopsis thaliana and rice (Oryza sativa), and in other plants as well have revealed that some factors such as organic acids (OAs), cell wall properties, phytohormones, and iron (Fe) homeostasis are interconnected with each other. Moreover, OAs are involved in recruiting of many plant-growth-promoting bacteria that are able to secrete both OAs and phosphatases to increase Pi availability and decrease Al toxicity. In this review paper, we summarize these mutual mechanisms by which plants deal with both Al toxicity and P starvation, with emphasis on OA secretion regulation, plant-growth-promoting bacteria, transcription factors, transporters, hormones, and cell wall-related kinases in the context of root development and root system architecture remodeling that plays a determinant role in improving P use efficiency and Al resistance on acidic soils. [ABSTRACT FROM AUTHOR]

Aluminum-activated root malate and citrate exudation play an important role in plant Al tolerance. This paper characterizes AtMATE, a homolog of the recently discovered sorghum and barley Al-tolerance genes, shown here to encode an Al-activated citrate transporter in Arabidopsis. Together with the previously characterized Al-activated malate transporter, AtALMT1, this discovery allowed us to examine the relationship in the same species between members of the two gene families for which Al-tolerance genes have been identified. AtMATE is expressed primarily in roots and is induced by Al. An AtMATE T-DNA knockdown line exhibited very low AtMATE expression and Al-activated root citrate exudation was abolished. The AtALMT1 AtMATE double mutant lacked both Al-activated root malate and citrate exudation and showed greater Al sensitivity than the AtALMT1 mutant. Therefore, although AtALMT1 is a major contributor to Arabidopsis Al tolerance, AtMATE also makes a significant but smaller contribution. The expression patterns of AtALMT1 and AtMATE and the profiles of Al-activated root citrate and malate exudation are not affected by the presence or absence of the other gene. These results suggest that AtALMT1-mediated malate exudation and AtMATE-mediated citrate exudation evolved independently to confer Al tolerance in Arabidopsis. However, a link between regulation of expression of the two transporters in response to Al was identified through work on STOP1, a transcription factor that was previously shown to be necessary for AtALMT1 expression. Here we show that STOP1 is also required for AtMATE expression and Al-activated citrate exudation. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aluminum is inevitable component of many vaccines. The benefit of the vaccines is undeniable but effects of aluminum toxicity might be underestimated and neglected. In this review, we highlighted the mechanims of aluminum toxicity, which is still in debate. So far, all the papers that disscused the adverse aluminum effects pointed two mechanisms responsible for Al toxicity, direct Al toxicity and aluminum induced cell damage via the oxidative metabolism. According to our knowledge, which is based on basic principles of biochemistry and inorganic chemistry, we suggested that aluminum highly interferes with iron metabolism eventually resulting in iron-mediated cell damage. More importantly, in this paper, we offered easily feasible solutions, in order to avoid aluminum toxicity in the future. We suggest that as it once was, Calcium Phosphate again to be used as the adjuvant or better solution that the vaccine adjuvants should be based on zinc compounds or even better would be non-metal adjuvants, such as microcrystalline tyrosine and monosodium urate. Until an adequate adjuvant is provided, we suggest instant postponement of vaccination with vaccines which use aluminum as the adjuvant until the 12 months of age. [ABSTRACT FROM AUTHOR]

Damage to Japanese cedars caused by the sugi bark borer in plots with low, medium and high planting density (1,700, 3,200, and 7,300 trees/ha, respectively) was examined in a 20-year-old sugi plantation. Radial growth and annual ring-width at breast height of three trees sampled per plot were measured by stem analysis. Stand age when each pupal chamber formed on the sample trees by the borer was also investigated by sawing the trees. There was less damage in the high density plot than in the low density plot. Radial growth at breast height increased rapidly from the 7th year after planting in all plots. The width of the annual ring reached a maximum in the 9th or 10th year, and decreased gradually thereafter. Radial growth in the low density plot was larger than that in the high density plot. Pupal chambers were first observed in the 7th year. The number of pupal chambers increased yearly, reaching a maximum in the 12th or 13th year, and decreased rapidly thereafter. These results indicate that restriction of radial growth of trees in the juvenile period by high density planting can prevent infestation of the sugi bark borer. In this study, we measured the positioning accuracy of the Global Positioning System (GPS) while walking in forested areas and analyzed the GPS data to find factors that affected the positioning accuracy. In the field tests, we repeated GPS measurements with different types of GPS receivers, types of forests and modes of GPS positioning. The GPS data were analyzed using ANOVA. As a result, the type of GPS receivers, type of forests and modes of GPS positioning were found to be a significant factor (P < 0.001) to determine positioning accuracy while any interactions between these factors were not. The result also showed that the GPS receiver with multipath rejection technology produced higher positioning accuracy than without it. Therefore, multipath errors, which are caused by the reflection of GPS signals due to nearby stems, can be a critical cause to adversely affect GPS positioning accuracy. It was also suggested that GPS positioning accuracy while walking in forested areas was affected not by basal area but by stand density. That was because temporal signal blocking occurred more often with increasing stand density while walking forested areas. As a result of multiple regression analysis, the observed Position Dilution of Precision (PDOP) was not a significant factor (P = 0.590) to determine positioning accuracy. Deciduous oak (Quercus serrata) forest is a major vegetation type of temperate broad-leaved forests in the north Kanto Region, Japan. The objective of this study is to examine the past and present human-use of the forests and to foresee the future prospects. The shiitake mushroom (Lentinus edodes) producing districts in Saitama and Tochigi were selected as the study areas. Until the 1960s more than 70% of local broad-leaved forests were used as fuelwood in the areas studied. After the revolutionary change in the forms of energy used in the 1960s, oak forests turned to being used mainly for shiitake cultivation in many rural areas. Most oak logs for shiitake have been provided within the shiitake-producing area, but in recent years the number of logs brought from other areas is increasing in fresh shiitake cultivation. Because of the rapid expansion of shiitake imports, aging of the domestic cultivators and labor shortage, domestic shiitake cultivation has declined conspicuously for the last 15 years. In addition, many forest owners and cultivators have already stopped managing the forests as they used to. As a result, if the shiitake cultivation continues to shrink, it is estimated that around 90% of the local broad-leaved forests will be abandoned by the year of 2,015 even in shiitake-producing areas. This paper describes our comparative study on forest policies in Japan, the United States, and Sweden (EU) to assess the policies of Japan for preventing global warming. The forest policies in these three countries were compared in terms of the process of policy-making, overview of policy execution, forest management, forest conservation and protection, conserved and reserve forests, urban forests, biomass utilization, forest studies and indirect slash tools, and policies for attaining the goal of the first period. The forest policies of Japan are characterized by the use of non-physical methods of CO2 absorption, such as cultivating sound forests, managing reserve forests, promoting the use of biomass, and educating people. The United States has substantial policies for physical methods for actively absorbing CO2, such as planting trees. However, the US has not been able to acquire sufficient funds for the policies, and the target absorption has not been attained. Sweden has tended to use non-physical methods and has substantial policies for promoting the certification system, assigning conservation areas, and promoting the use of biomass energy. Hydrological control of streamwater NO3- concentrations was investigated in a weathered granitic headwater forest catchment. The catchment was divided into three parts: the stream channel area, the soil sedimentation area, and the hillslope area connected to the soil sedimentation area. The discharge rate of saturated throughflow within the hillslope and catchment and the groundwater levels in the soil sedimentation area were measured in tandem with the hydrochemical observations. At the points observed, the streamwater had the lowest NO3- concentrations. The concentrations were low during baseflow conditions and increased with the discharge rate. Considering the water budget in the hillslope, about half of the total rainfall infiltrated into the bedrock. This bedrock groundwater was the dominant component of the baseflow, with low NO3- concentrations, while groundwater in the soil sediment area with relatively high concentrations flowed into the stream during rainstorms. The dynamics of the streamwater NO3- concentrations were strongly affected by the hydrological processes in the forest catchment. Especially, the baseflow NO3- concentrations were kept low by the groundwater flow passing through the bedrock. The objective of this study is establishment of vegetative propagation of Japanese black pine (Pinus thunbergii). We examined the effect of defoliation, disbudding and shape of basal cut on the rooting ability of cuttings, and we tried to find an optimal method of propagation. Cuttings were made from terminal shoots of 1-year-old seedlings. As a result, 1) When 0–46% of the needles of cuttings were removed, those rooting percentages were steady between 54 and 62%. However, when needles were removed excessively, rooting ability decreased notably. Moreover, 46% needle removal cuttings had the longest root systems. 2) In the case of cuttings with a part or all their buds removed, the rooting percentage was greater than that of control cuttings. 3) On the examination of treatments of the cut end, rooting ability was better for diagonal shape than for horizontal shapes, but difference in the effect was insignificant. So the optimal method is to remove half of the needles or buds from cuttings and to cut end in a diagonal shape. However, as growth of cuttings from which buds had been removed was bad, a careful needs to be paid to disbudding for commercial production. Chlorophyll fluorescence methods have been used to evaluate the effects of environmental stresses on photosynthetic properties. Chlorophyll fluorescence can provide detailed information of photosystem II (PSII) photochemistry, which is vulnerable to environmental stresses such as strong light, low temperature, heat and drought. I reviewed photoinhibition of photosynthesis and discussed the mechanism to prevent photoinhibition in drought-acclimated leaves. As drought stress is often accompanied by strong light, a decline in photosynthesis caused by stomatal closure increases the risk of photoinhibition. Energy dissipation via electron flow would be an effective way to prevent photodamage as well as thermal energy dissipation in PSII antennae. When plants are illuminated by excess light, inhibition of photosynthesis occurs by harmful molecules generated by excess excitation energy. Photochemical efficiency is also decreased during the dissipation of excitation energy by protective mechanism. Inhibition of photosynthesis by low temperature results in a considerable excess of excitation energy leading to photodamage. Although evergreen woody plants are considered to be subjected to photoinhibition, they develop many photoprotective mechanisms against photoinhibition. In this review, I summarized the molecular aspects of photoinhibition and role of photoprotective mechanisms, and discus the ecophysiological meanings of photoprotections, especially xanthophyll cycle, water-water cycle, and photodynamic screen provided by the accumulation of pigments such as rhodoxanthin and anthocyanine observed in over-wintering woody plants. Acid fog is considered to have a large influence on tree physiology because it has a high concentration of air pollutants and is persistent in the atmosphere. Long-range transported pollutants contribute to acidification of fog in mountainous areas and therefore trees grown in these areas are thought to be affected by acid fog. The effects of acid fog using tree seedlings are well documented. From the results of these experimental studies, acid fog is known to induce visible injury, reduce the dry weight and photosynthesis systems, disintegrate the epicuticular wax, alter the nutrient status, and increase the sensitivity to other stresses, such as frost, wind and ozone. In addition, the extent of these effects is dependent on the pH and the components of acid fog and tree species. In this review, we summarize these reports and discuss further developments in research. Degraded lands abandoned after failures of agricultural development are widely distributed over tropical areas. – Environmental reforestation – in degraded lands is needed for the rehabilitation of regional environments. In this paper, I review properties of problem soils in tropical Asia and stress responses of tropical trees, and discuss the development of methods of environmental reforestation. Food shortage and environmental deterioration due to rapid growth of the global population are the most serious problems that face us human beings. Improvement of tolerance of plants to abiotic stresses such as drought, high salinity, low temperature, and heat is one of the promising approaches for the future of agriculture and environmental conservation. It is essential to know at first how plants respond to environmental stresses and which molecules are involved in stress tolerance. According to recent development in genomics in Arabidopsis, it has been shown that hundreds of genes are involved in stress response and/or stress tolerance. More recently, functional genomics in woody plants has been promoted mainly in the occident. A US group, in particular, is determining the nucleotide sequence of whole poplar genome, and this information will have been released by the end of the year 2003. We are convinced that the poplar will be more important as a model forest tree in the post-genome era. We here introduce the world-wide situation of genomics in the poplar and discuss a direction of study on stress physiology in woody plants. Genetic engineering has the potential to allow the selective improvement of individual traits in woody plants without the loss of any of the desired trait of the parental line. Using such techniques, we can overcome the difficulties associated with the breeding of long-lived perennials, which need to long time to produce progeny. In this paper, we introduce recent advances in the application of genetic engineering to forest trees to solve environmental problems. And, we also discuss the necessity of flowering control of transgenic woody plants. [ABSTRACT FROM AUTHOR]

Aluminum (Al) is the most prevalent element in the earth crust and is toxic to plants in acidic soils. However, plants can address Al toxicity through external exclusion (which prevents Al from entering roots) and internal detoxification (which counterbalances the toxic-Al absorbed by roots). Nowadays, certain categories of exogenously added regulatory factors (EARF), such as nutritional elements, organic acids, amino acids, phytohormones, or biochar, etc. play a critical role in reducing the bioavailability/toxicity of Al in plants. Numerous studies suggest that regulating factors against Al toxicity mediate the expression of Al-responsive genes and transcription factors, thereby regulating the secretion of organic acids, alkalizing rhizosphere pH, modulating cell wall (CW) modifications, improving antioxidant defense systems, and promoting the compartmentalization of non-toxic Al within intracellular. This review primarily discusses recent and older published papers to demonstrate the basic concepts of Al phytotoxicity. Furthermore, we provide a comprehensive explanation of the crucial roles of EARF-induced responses against Al toxicity in plants. This information may serve as a foundation for improving plant resistance to Al and enhancing the growth of susceptible species in acidic soils. And this review holds significant theoretical significance for EARF to improve the quality of acidic soils cultivated land, increase crop yield and quality, and ensure food security. [Display omitted] • EARF influences rhizosphere pH and Al availability, reduces its absorption by root. • EARF regulates organic acids secretions in the tolerance to Al toxicity. • EARF modulates Al toxicity by reducing Al deposition in cell wall. • EARF protects Al-induced inhibition by regulating antioxidant defense system. • EARF chelates and separates Al to vacuoles to reduce its toxicity. [ABSTRACT FROM AUTHOR]

Biomineralization in plant roots refers to the process of cell-induced self-assembly to form nanostructures on the root surface. Silicon (Si) is the second most abundant element in soils, and beneficial to plant growth. Meanwhile, silicon is shown to participate in the process of biomineralization, which is useful for improving mechanical strength and alleviating biotic and abiotic stress, for example silicic acid polymerizes to form amorphous silica (SiO2–nH2O) in the process of growing to resist fungi and environmental stress. This process alters physical and chemical properties of cell wall. However, the mechanistic basis of this process remains unclear. Aluminum toxicity is a major constraint affecting plant performance in acid soil. This paper summarizes recent research advances in the field of plant biomineralization and describes the effects of silicon biomineralization on plant aluminum tolerance and its adaptive significance, using aluminum toxicity as a case study.

Globally, more than half of potentially arable land is acidic, and aluminum (Al) is the primary factor limiting plant growth and crop productivity on acidic soils worldwide. The development and utilization of Al-tolerant crops is a sustainable approach to enhancing crop production on acidic soils. For this purpose, screening available genetic resources under Al-stressed conditions is a crucial initial step. Hence, the present study aimed to evaluate the Al tolerance of 264 Ethiopian chickpea landraces under hydroponic conditions without Al (control) and with 120 µM Al (Al treatment). Significant (p < 0.001) variations were detected among the genotypes for all studied traits under control (0 µM Al) and 120 µM Al concentration. The relative growth values for the 120 µM Al/0 µM Al ratio was also significant, indicating the presence of a considerable amount of genetic variation in Ethiopian chickpea landraces in terms of Al tolerance. Based on relative root growth (RRG) as an Al-tolerance parameter, the genotypes were grouped into five distinct (p < 0.001) classes. The highest RRG value (1.59) was obtained for genotype ETC_209008, followed by ETC_41184 and ETC_212589, while ETC_208995 had the lowest RRG value of 0.27. Of the total landraces screened, 35% had higher RRG values than the tolerant genotype ETC_WL_1_2016 used as a reference, indicating the presence of adequate genotypes capable of outperforming the reference genotype on acidic soils. The genotypes identified in the present study may serve as sources of novel alleles in genes regulating Al tolerance in chickpea that can be utilized in breeding programs to improve the crop's adaptation to acidic soils, thus contributing to smallholder farmers' increased nutritional and food security. [ABSTRACT FROM AUTHOR]

The toxicity of aluminum (Al) in acidic soils poses a significant limitation to crop productivity. In this study, we found a notable increase in DnaJ (HSP40) expression in the roots of Al-tolerant alfalfa (WL-525HQ), which we named MsDjB4. Transient conversion assays of tobacco leaf epidermal cells showed that MsDjB4 was targeted to the membrane system including Endoplasmic Reticulum (ER), Golgi, and plasma membrane. We overexpressed (MsDjB4-OE) and suppressed (MsDjB4-RNAi) MsDjB4 in alfalfa hairy roots and found that MsDjB4-OE lines exhibited significantly better tolerance to Al stress compared to wild-type and RNAi hairy roots. Specifically, MsDjB4-OE lines had longer root length, more lateral roots, and lower Al content compared to wild-type and RNAi lines. Furthermore, MsDjB4-OE lines showed lower levels of lipid peroxidation and ROS, as well as higher activity of antioxidant enzymes SOD, CAT, and POD compared to wild-type and RNAi lines under Al stress. Moreover, MsDjB4-OE lines had higher soluble protein content compared to wild-type and RNAi lines after Al treatment. These findings provide evidence that MsDjB4 contributes to the improved tolerance of alfalfa to Al stress by facilitating protein synthesis and enhancing antioxidant capacity. [ABSTRACT FROM AUTHOR]

Acid soils occupy approximately 50% of potentially arable lands. Improving crop productivity in acid soils, therefore, will be crucial for ensuring food security and agricultural sustainability. High soil acidity often coexists with phosphorus (P) deficiency and aluminum (Al) toxicity, a combination that severely impedes crop growth and yield across wide areas. As roots explore soil for the nutrients and water required for plant growth and development, they also sense and respond to below-ground stresses. Within the terrestrial context of widespread P deficiency and Al toxicity pressures, plants, particularly roots, have evolved a variety of mechanisms for adapting to these stresses. As legumes, soybean (Glycine max) plants may acquire nitrogen (N) through symbiotic nitrogen fixation (SNF), an adaptation that can be useful for mitigating excessive N fertilizer use, either directly as leguminous crop participants in rotation and intercropping systems, or secondarily as green manure cover crops. In this review, we investigate legumes, especially soybean, for recent advances in our understanding of root-based mechanisms linked with root architecture modification, exudation and symbiosis, together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils. We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions. [ABSTRACT FROM AUTHOR]

Background and Aims: Suitable N source supply is critical to improve plant growth and N uptake, but the importance of nitrate (NO3−) for rice (Oryza sativa L.) and microbiota is often neglected in acidic paddy soils where ammonium (NH4+) is dominant. This study aimed to explore the differential effects of NH4+ and NO3− on rice growth, fertilizer nitrogen recovery efficiency (FNRE), and rhizosphere bacterial community in acid soil. Methods: Two rice varieties, Kasalath (Al-sensitive indica) and Koshihikari (Al-tolerant japonica), were exposed to different N sources with or without lime in an acid soil. Results: Liming and NO3− application solely improved the growth and FNRE of the Al-sensitive rice, namely, by increasing soil pH and alleviating Al toxicity. Compared with liming and rice variety, N source had a more pronounced influence on rhizobacterial community composition. Of the two sources, NO3− had a stronger effect on the rhizobacterial community than NH4+. Remarkably, rice plants fed with NH4+ specifically recruited Desulfosporosinus and Desulfitobacterium associated with ferric NH4+ oxidation in the rhizosphere, whereas those exposed to NO3− recruited Alicyclobacillus with NO3−-reducing iron oxidation ability. Three keystone taxa were identified in a rhizobacterial co-occurrence network analysis: Alicyclobacillus, which was positively associated with rice growth and FNRE, and Acidobacteriales and WPS-2, both with negative associations. Conclusion: Compared with NH4+, NO3− enhances the growth and FNRE of Al-sensitive rice and exerts dominant effects on the rhizobacterial community, which indicates the importance of NO3− for rice and has instructive implications for N management in acid soil. [ABSTRACT FROM AUTHOR]

Soil acidity or aluminum (Al) toxicity is a major limitation to crop production. In this paper, we examine the effects of surface-applied lime and gypsum on soil profile chemical properties that affect Al toxicity in short-term (1 year), medium-term (2 years and 8 months) and long-term (10 years) experiments. Sulfate applied to the soil surface as gypsum was leached rapidly to a depth of 40 cm in the short-term despite relatively low amounts (279 mm) of rainfall. In the medium and long-term experiments, 28–54% of the sulfate applied as gypsum was retained in the 0–50 cm soil layer due to adsorption and precipitation reactions. The combined application of lime and gypsum increased soil calcium, to a depth of 30 cm in the short-term and to a depth of 50 cm in the medium and long-terms. Increases in soil sulfate and calcium were associated with greater electrical conductivity to a depth of 50 cm for all sampling times. Application of lime alone had no impact on soil Al, pH, and calcium in the soil layers below 10 cm in the short and medium terms. In the long-term, increasing the rate of lime application from 2 to 8 t L ha−1 increased soil pH in the 10–20 cm soil layer while soil Al decreased to a depth of 30 cm. The combined use of lime and gypsum decreased soil Al in the 30–50 cm soil layer in the medium-term and the 20–30 cm soil layer in the long-term which was more than when only lime was applied. Hence, we recommend the use of lime plus gypsum for treating soils with subsoil Al toxicity. Additionally, soil Al measurements are a more sensitive measurement of the impact of surface application lime and lime plus gypsum than soil pH. [ABSTRACT FROM AUTHOR]

North-Eastern India is blessed with a vast diversity of rice genotypes with varying yielding abilities. However, the predominant strong soil acidity induced nutrient stresses from the toxicity of aluminum (Al3+) ions often causes sub-optimal rice productivity. The lack of suitable nutrient media for the screening of aluminum (Al) toxicity tolerance of rice genotypes is one of the limiting factors in Al tolerant varieties' development. Modified Magnavaca's solution has been the most recommended nutrient solution for this purpose where ammonium nitrate is the primary nitrogen source. However, strict regulations related to the handling and storage of ammonium nitrate in India limit the preparation of Modified Magnavaca's solution for laboratory use. Here, a modified ammonium nitrate-free formulation based upon the Magnavaca's solution has been proposed. The modified formulation was found to have 160.9 µM of active Al3+ concentration when 550 µM of aluminum chloride hexahydrate (AlCl3.6H2O) was added at pH 4.1 to the solution. Through a plant growth screening experiment using ten diverse rice genotypes a significant difference in the response of various genotypes to differential Al toxicity levels on root growth performance indicators was observed. Based on the response, we could able to categorize the genotypes into tolerant and sensitive in relative terms. Thus, the present experiment provided an important nutrient formulation suitable for screening rice genotypes under Al toxicity conditions. Moreover, the selected tolerant and sensitive genotypes can further pave the way for studying the molecular mechanism of Al toxicity response in rice and their use in the breeding program. [ABSTRACT FROM AUTHOR]

Genetic variation in wild relatives, GenBank accessions, landraces, and cultivars can unlock key alleles for the traits of interest for breeding programs. Breeding programs often utilize different strategies to quantify the source of heritable variation for target traits. One neglected area of study is the root traits of diverse genotypes, and this is especially the case for aluminum toxicity effects on legumes such as the common bean, which is the most used pulse for direct human consumption. This study evaluated 267 genotypes of common bean that were part of the global Andean Diversity Panel (ADP), consisting mainly of genotypes assembled from public and private breeding programs in Africa and North America, as well as elite lines and land races from the USDA. The ADP was evaluated for root traits at the seedling stage in the Tennessee State University (TSU) greenhouse using a hydroponic system with a standard nutrient solution with and without aluminum (Al). The recorded data on the roots per trial were fit to a linear mixed model for the analysis of variance in order to test for the genotype differences. Adjusted means considered replication and blocks within replication as random effects and genotypes as fixed effects. These were then used for Pearson correlation tests and for principal component analysis (PCA), where the first two vectors accounted for 94.5% and 93% of the explained variation under the control and Al-treatment conditions, respectively. Genotypes were clustered based on the morphology of roots in response to Al-toxicity treatment using the Euclidean distance and Ward's hierarchical agglomerative clustering method, identifying four distinctive groups significant at p < 0.01. The intra-cluster distance was lower than the inter-cluster distances, which indicated a heterogeneous and homogeneous nature between and within clusters, respectively. The results suggest that crossing between accessions from two of the clusters would result in the maximum genetic segregation. One cluster was found to have a higher Al-toxicity tolerance than the others. [ABSTRACT FROM AUTHOR]

Due to anthropogenic activities and the advancement of industries, metal contamination is growing globally. Aluminum toxicity is seriously endangering plants, animals, and humans by rapidly rising in soil and water. Even though some fungi can tolerate aluminum, researchers are interested in finding bacteria that are resistant to aluminum. The current state of knowledge on bacteria resistant to aluminum is extremely limited. In the present study, bacterial isolates from soil near a metal electroplating and automobile industry in Punjab, India, were isolated and then screened for high aluminum metal tolerance. The aluminum tolerant bacterial isolate was identified as Cedecea davisae M1, a member of the Enterobacteriaceae family, using morphological, biochemical, and 16srRNA gene sequence analyses. The spectroscopic results indicate that the strain may tolerate up to 150 ppm of aluminum. Antibiotic resistance of Cedecea davisae M1 was determined using disks on Luria agar plates, and the bacteria were found to be resistant to vancomycin, ampicillin, carbenicillin, and rifampicin. The findings of the study indicated that the strain might be able to remove aluminum toxicity from the environment, which needs to be further explored. [ABSTRACT FROM AUTHOR]

Soil acidity threatens food production in the tropics. The effect of increasing ammonium-based fertilizer (INF) on soil pH was assessed in sub-Saharan Africa (SSA). A total of 9043 soil data from Africa soil information services, past INF use, and two future scenarios of INF use (business as usual (BAU) and equitable diet (EqD)) were used to determine soil pH variations from 1980 to 2022 and to predict soil PH variations from 2022 to 2050. Random forest and extreme gradient boosting algorithms and soil-forming factor covariates were used for the spatio-temporal soil pH predictions. Topsoil acidification was shown to be significant, with mean annual decrements of 0.014, 0.024, and 0.048 from 1980 to 2022, 2022 to 2050 (BAU), and 2022 to 2050 (EqD), respectively. Over the past 42 years, croplands with soil pH < 6.5 have declined significantly, and soil acidification is predicted to become severe by 2050 in the BAU and EqD scenarios. This was indicated by a predicted 3% increase in croplands at risk of aluminum toxicity (soil pH < 5.5) from 66 × 106 ha in 2022 to 78.5 × 106 ha in 2050. The drivers of the spatial variations in the soil pH between 1980 and 2050 were the MAP, basic cation, clay content, SOC, and nitrogen fertilizers. The evaluation metrics of the 10-fold cross-validation showed that the root mean squared errors (RMSEs) of the soil pH from 1980 to 2022, as well as the predicted soil PH from 2022 to 2050 (BAU) and 2022 to 2050 (EqD), were 0.53 pH units, 0.54 pH units, and 0.56 pH units, respectively, with coefficients of determination (R2) of 0.63, 0.64, and 0.66. The findings of this study can be used for the establishment of management strategies for increasing INF use in acidic soils. [ABSTRACT FROM AUTHOR]

Secretion of oxalic acid from roots is an important aluminum detoxification mechanism for many plants such as Hevea brasiliensis (rubber tree). However, the underlying molecular mechanism and oxalate transporter genes in plants have not yet been reported. In this study, the oxalate transporter candidate genes HbOT1 and HbOT2 from the rubber tree were cloned and preliminarily identified. It was found that HbOT1 had a full length of 1163 bp with CDS size of 792 bp, encoding 263 amino acids, and HbOT2 had a full length of 1647 bp with a CDS region length of 840 bp, encoding 279 amino acid residues. HbOT1 and HbOT2 were both stable hydrophobic proteins with transmembrane structure and SNARE_assoc domains, possibly belonging to the SNARE_assoc subfamily proteins of the SNARE superfamily. qRT-PCR assays revealed that HbOT1 and HbOT2 were constitutively expressed in different tissues, with HbOT1 highly expressed in roots, stems, barks, and latex, while HbOT2 was highly expressed in latex. In addition, the expressions of HbOT1 and HbOT2 were up-regulated in response to aluminum stress, and they were inducible by metals, such as copper and manganese. Heterologous expression of HbOT1 and HbOT2 in the yeast mutant AD12345678 enhanced the tolerance to oxalic acid and high concentration aluminum stress, which was closely correlated with the secretion of oxalic acid. This study is the first report on oxalate transporter genes in plants, which provides a theoretical reference for the study on the molecular mechanism of oxalic acid secretion to relieve aluminum toxicity and on aluminum-tolerance genetic engineering breeding. [ABSTRACT FROM AUTHOR]

The rampant bayberry decline disease has been regarded as related to soil with the long-term plantation bayberry. These parameters, hydrogen, aluminum, other alkali cations, and plant-related nutrients, were measured from the soil around diseased tree roots 10, 20, and 30 years old. The pH significantly declined in topsoil with increasing tree age and rose with increasing depth of the soil layer with an age of 10, 20, and 30 years. The concentration of exchangeable aluminum has risen significantly with the increase of the tree ages in the top soil layer and also in 0 to 40 cm soils layer with ten-year-old trees. In the top soil layer with a depth of 0 to 10 cm, the cation concentrations of Ca2+, Mg2+, and K+ has fallen significantly with the increase of tree ages. A higher concentration of exchangeable aluminum was observed in the soil with trees more seriously affected by the disease and was accompanied with lower concentrations of Ca2+, Mg2+, and K+. The correlation analysis showed that the soil pH is significantly positively related to the concentration of exchangeable Ca2+, total nitrogen, and total phosphorus and negatively to exchangeable aluminum. These findings provided a new insight to mitigate the disease by regulating the soil parameters. [ABSTRACT FROM AUTHOR]

SUMMARY: Aluminum (Al) toxicity severely restricts plant growth in acidic soils (pH < 5.0). In this study, an R2R3‐MYB transcription factor (TF) gene, MsMYB741, was cloned from alfalfa. Its function and gene regulatory pathways were studied via overexpression and RNA interference of MsMYB741 in alfalfa seedlings. Results showed that root elongation increased as a result of MsMYB741 overexpression (MsMYB741‐OE) and decreased with MsMYB741 RNA interference (MsMYB741‐RNAi) in alfalfa seedlings compared with the wild‐type under Al stress. These were attributed to the reduced Al content in MsMYB741‐OE lines, and increased Al content in MsMYB741‐RNAi lines. MsMYB741 positively activated the expression of phenylalanine ammonia‐lyase 1 (MsPAL1) and chalcone isomerase (MsCHI) by binding to MYB and ABRE elements in their promoters, respectively, which directly affected flavonoid accumulation in roots and secretion from root tips in plants under Al stress, eventually affecting Al accumulation in alfalfa. Additionally, MsABF2 TF directly activated the expression of MsMYB741 by binding to the ABRE element in its promoter. Taken together, our results indicate that MsMYB741 transcriptionally activates MsPAL1 and MsCHI expression to increase flavonoid accumulation in roots and secretion from root tips, leading to increased resistance of alfalfa to Al stress. Significance Statement: MsMYB741 is a key MYB transcription factor that promotes aluminum resistance of alfalfa via regulating flavonoid biosynthesis and secretion through directly activating MsPAL1 and MsCHI expression. Additionally, MsMYB741 is targeted by MsABF2, which is activated by ABA. [ABSTRACT FROM AUTHOR]

Purpose: The recent increase in aluminum exposure and its effect on the development of the brain call for serious attention. The study investigated the behavioral and immunohistochemical changes in the cerebral cortex of Wistar rats following prenatal co-administration of ethyl acetate leaf fraction of Tamarindus indica (EATI) and aluminum chloride (AlCl3). Methods: Pregnant Wistar rats were divided into 5 groups (n=4). Group I (negative control), Group II–V were experimental groups treated with 200 mg/kg of AlCl3 s/c. Group III and IV received an additional 400 mg/kg and 800 mg/kg of EATI respectively, while Group V received an additional 300 mg/kg of Vitamin E for 14 days (prenatal days 7– 21) via the oral route. The pups were then exposed to cliff avoidance, negative geotaxis, and elevated plus maze (EPM) test on the post-natal day (PoND) 4– 6, 7– 10, and 18 respectively. On PoND 21 pups were sacrificed, and the skull dissected to remove the brain. The harvested brain tissues were processed for Cresyl fast (CF) and glial fibrillary acid protein (GFAP). Results: The study showed that EATI administration during AlCl3 exposure was associated with significant improvement in sensory-motor development. The EPM, CF, and GFAP results revealed significant improvement in anxiety-like behavior, motor activities, GFAP expression, pyramidal cell count, and Nissl staining following prenatal EATI administration during AlCl3 exposure. Conclusion: The present study concludes that EATI was associated with some protective potential during prenatal AlCl3 exposure in Wistar rats. Graphical [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency and aluminum (Al) toxicity often coexist and are two major limiting factors for crop production in acid soils. The purpose of this study was to characterize the function of GmBBE-like43, a berberine bridge enzyme-like proteinencoding gene, in soybean (Glycine max) adaptation to Al and low P stresses. Present quantitative real-time PCR (qRT-PCR) assays confirmed the phosphate (Pi)-starvation enhanced and Al-stress up-regulated expression pattern of GmBBE-like43 in soybean roots. Meanwhile, the expression of a GmBBE-like43-GFP chimera in both common bean hairy roots and tobacco leaves demonstrated its cell wall localization. Moreover, both transgenic Arabidopsis and soybean hairy roots revealed the function of GmBBE-like43 in promoting root growth under both Al and low P stresses. GmBBE-like43-overexpression also resulted in more H2O2 production on transgenic soybean hairy root surface with oligogalacturonides (OGs) application and antagonized the effects of Al on the expression of two SAUR-like genes. Taken together, our results suggest that GmBBE-like43might be involved in the soybean's coordinated adaptation to Al toxicity and Pi starvation through modulation of OGs-oxidation in the cell wall. [ABSTRACT FROM AUTHOR]

Aluminum (Al) solubilizes into trivalent ions (Al3+) on acidic soils, inhibiting root growth. Since about 13% of global rice cultivation is grown on acidic soils, improving Al tolerance in rice may significantly increase yields. In the present study, metabolome analysis under Al toxicity between the Al-tolerant variety Nipponbare and the Al-sensitive variety H570 were performed. There were 45 and 83 differential metabolites which were specifically detected in Nipponbare and H570 under Al toxicity, respectively. Furthermore, the results showed that 16 lipids out of 45 total metabolites were down-regulated, and 7 phenolic acids as well as 4 alkaloids of 45 metabolites were up-regulated in Nipponbare, while 12 amino acids and their derivatives were specifically detected in H570, of which 11 amino acids increased, including L-homoserine and L-methionine, which are involved in cysteine synthesis, L-ornithine and L-proline, which are associated with putrescine synthesis, and 1-aminocyclopropane-1-carboxylate, which is associated with ethylene synthesis. The contents of cysteine and s-(methyl) glutathione, which were reported to be related to Al detoxification in rice, decreased significantly. Meanwhile, putrescine was accumulated in H570, while there was no significant change in Nipponbare, so we speculated that it might be an intermediate product of Al detoxification in rice. The differential metabolites detected between Al-tolerant and -sensitive rice variants in the present study might play important roles in Al tolerance. These results provide new insights in the mechanisms of Al tolerance in rice. [ABSTRACT FROM AUTHOR]

The decline disease of Myrica rubra tree is commonly induced by soil acidification, which affects the yield and the quality of fruits. It is hypothesized that aluminum toxicity and microbial community changes caused by soil acidification were the main causes of decline of Myrica rubra tree. In order to explore the decline mechanism of Myrica rubra tree, soils around healthy and decline trees of Myrica rubra were collected to compare the concentrations of different aluminum forms, enzyme activities, and bacterial community structure. In this study, soil samples were collected from the five main production areas of Myrica rubra, Eastern China. The results showed that diseased soils had higher exchangeable aluminum, lower enzyme activities, and lower microbial diversity than healthy soils at various sites. The toxic Al significantly decreased bacterial diversity and altered the bacterial community structure. The diseased soils had significantly lower α-diversity indices (ACE, Chao1, and Shannon) of bacterial community. The Al toxicity deceased the relative abundance of Acidobacteria and Planctomycetes, while enhanced the relative abundance of Cyanobacteria, Bacteroidetes, and Firmicutes in soils. Co-occurrence network analysis indicated that the Al toxicity simplified the bacterial network. The soil ExAl content was significantly and negatively correlated with the nodes (r = -0.69, p < 0.05) and edges (r = -0.77, p < 0.01) of the bacterial network. These results revealed that the Al toxicity altered soil bacterial community structure, resulting in the decline disease of Myrica rubra tree, while highlighted the role of Al forms in the plant growth. This finding is of considerable significance to the better management of acidification-induced soil degradation and the quality of fruits. [ABSTRACT FROM AUTHOR]

Root border cells (RBCs) are a group of cells that originated from the root cap meristem, which are developed by genetic regulation and play a variety of biological functions. Being composed of a homologous single cell population with high metabolic activity and intact cell walls, RBCs represent a highly useful tool for studying various aspects of plant mineral absorption and utilization, as well as plant-soil-microbiome interactions in the rhizosphere. Research on RBCs also promise to become a hotspot in the context of understanding root adaptive responses to hostile environments. In order to take advantage of RBCs as an ideal single cell system in plant-environmental interactions, we summarized the production and function of RBCs and built-up the methodology for RBCs culturing, purification, and quantity control for plant research. The latter is done by using a case study of the application of RBCs to study mechanisms of Al toxicity in plants. This work offers plant scientists a new cognition of adopting RBCs as a convenient single cell system for the multidisciplinary research including (but not limited to) plant physiology, development and genetics, nutrition, and stress and adaptation. Root border cells (RBCs) are derived from the root cap and represent a population of living cells with special physiological activity and biological roles that are different from the root cap cells per se. After being separated from the root cap, RBCs become more active in metabolism than the progenitor root cap cells; for example, they incorporate labeled amino acids into protein 2.6-fold more efficiently than the cells of the root cap. In addition, mRNA and protein were differentially expressed between root cap cells and RBCs. Since the production of RBCs is genetically regulated and RBCs played a variety of biological functions in resistance to biotic and abiotic stresses occurred in the rhizosphere, RBCs were suggested as an ideal single cell system for the study the response of plant root cells to nutrient availability, environmental stresses, and in plant-microbial interactions. Some studies revealed that RBCs, which development is regulated by endogenous and exogenous signals, are biologically viable in the majority of higher plant species. This work reviews the research on RBCs in plant environment interaction and describes the case study of RBCs as a convenient single cell system to study plant responses to Al toxicity. [ABSTRACT FROM AUTHOR]

In this work, 75 quality protein maize (QPM) inbred lines were evaluated for aluminum tolerance using a nutrient solution assay in a laboratory and a soil-based technique in a greenhouse tunnel. The experiment was set up in a completely randomized design with three replications in the laboratory, and a randomized complete block design was used in the greenhouse. Aluminum toxicity was generated by amending a nutrient solution with 600 µM of aluminum sulfate (Al2 [SO4]3) in the laboratory, and Al2 [SO4]3 was applied at a rate of 24 mg kg−1 of soil in the greenhouse experiment. Relative root length (RRL) and hematoxylin staining (HS) scores were used to identify tolerant genotypes in the laboratory. According to RRL, 94.7% of genotypes were tolerant and 5.3% were sensitive, while Hematoxylin (HS) classified 77.9% of the genotypes as tolerant, and 22.1% as sensitive. RRL and HS presented a very strong negative association (−0.788). In the soil-based method, the experiments were conducted twice in successive summer seasons of 2019 and 2020. Several growth traits were measured and most genotypes that exhibited tolerance in the nutrient solution also had similar tolerance in the soil-based screening technique. Genetic variability for tolerance was identified, revealing potentially useful donors of tolerance genes in breeding programs. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity is a major abiotic stress that negatively impacts plant growth and crop productivity. Al ions are released into soil solutions as a function of soil pH, which is in turn determined by a combination of factors, including local geology, historic vegetation and land-use patterns. Selection and use of Al-tolerant crops is a preferred method to address the problem of Al toxicity. The present study evaluated a combination of modern cultivars, advanced breeding lines and a local landrace for Al tolerance using a seedling-based hydroponic assay. Two sequential experiments were conducted to score root and shoot traits in the presence of aluminum. Initially, six Al concentrations (0, 50, 100, 120, 150 and 200 µM) were tested on six chickpea genotypes to identify the single Al concentration that best discriminates among genotypes. Subsequently, 31 chickpea genotypes were evaluated at 0 and 120 µM Al. Progressive declines in trait values were observed in all genotypes with increasing Al, although the degree of sensitivity varied significantly among genotypes. Genotypes were evaluated both for total root length under 120 µM Al and for relative root growth compared to a 0 µM Al control treatment. Considering both parameters, we identified four tolerant chickpea genotypes (DZ-2012-CK-0237, Wollega LV, DZ-2012-CK-0233 and Natoli) and two sensitive genotypes (Akaki and Fetenech). Wollega LV is a local landrace obtained from acidic soil regions of Western Ethiopia, presenting the possibility that historical selection during cultivation on acidic soils might underlie its unusual tolerance. The aluminum tolerance traits identified here are candidates for introgression breeding of new Ethiopian chickpea varieties with potential to increase yield and expand the area of cultivation. [ABSTRACT FROM AUTHOR]

Background: aluminum toxicity is the most important factor limiting the growth of plants in acid soils, whereas current treatments are unfeasible. For this reason, alternatives are sought for, among which homeopathic treatment. Aims: this study aimed at evaluating the influence of homeopathic preparations Alumina 6cH, Alumina 12cH, Calcarea carbonica 6cH and Calcarea carbonica 12cH on the germination and vigor of lettuce seeds subjected to toxic levels of aluminum in paper-solution. At the same time, it was sought to develop a new procedure to apply homeopathic preparations in plants (pelleting). Methods: the statistical design was entirely randomized (CRD) with 6 treatments and 4 repetitions. Treatments included: 1) pelleted seeds/talc + Alum 6 cH; 2) pelleted seeds/talc + Alum 12cH; 3) pelleted seed/talc + Calc 6cH; 4) pelleted seeds/talc + Calc 12cH; 5) pelleted seeds/talc + distilled water; 6) non pelleted seeds (control). Variables evaluated were: germination percentage (GP), germination speed index (GSI) and radicle length (RL). Results: there was significant difference in GSI and RL - variables that reflect the vigor of seeds - between the samples treated with homeopathic preparations and the controls Conclusions: homeopathic preparations Alumina 6cH and 12cH and Calcarea carbonica 6cH and 12cH had significant effect on the vigor of lettuce seeds subjected to stress conditions. [ABSTRACT FROM AUTHOR]

Increasing areas of agricultural land in high rainfall areas of Sub-Saharan Africa (SSA), where crop production used to be reliable, are affected by soil acidity. This review focuses on the extent, causes and effect of soil acidity on soil properties and crop yield and its management from the context of SSA. Studies showed that the detrimental effects of soil acidity can be mitigated through liming, integrated acid soil management and the use of acid-tolerant germplasms. Application of lime resulted in yield increments of 34–252% in wheat, barley and tef, 29–53% in faba bean and soybean, and 42–332% in potato in Ethiopia, 111–182% in maize in Kenya, and 45–103% in Mucuna in Nigeria under moderate to severe acid soil conditions. This was accompanied by a corresponding increase in soil pH up to 1.9 units and a decrease in exchangeable acidity and aluminum up to 2.1 cmol kg−1. Use of acid-tolerant crop varieties such as maize expressing superior tolerance to Al toxicity resulted in a yield increase of 51% under low soil pH in Cameroon and Kenya. Overall, soil acidity covering ∼35% of SSA should be reclaimed with lime and integrated acid soil management interventions, which could significantly increase crop yield and enhance the resilience of the tropical agroecosystems.. [ABSTRACT FROM AUTHOR]