Boron Toxicity Research Articles

Boron application to pigeon pea [Cajanus cajan L.] improves crop productivity and boron nutrition in Typic ustochrept soils of North-Western India

Agricultural plants have shown narrow range between deficiency and toxicity of boron (B), thus its inadequate supply poses a detrimental effect on the crop yield by lowering the grain setting. Thus, the present study was conducted to optimize the adequate level of B soil application on widely consumed pigeon pea [Cajanus cajan L.] for higher yield. Boron was applied at 0.62, 1.25, 2.50, 5.0 and 10.0 kg ha−1 through soil application on Typic ustochrept soil. Boron fertigation at 1.25 kg ha−1 improved the number of filled pods possibly due to the facilitated pollen germination and tube growth which led to the fertilization, thus enhancing grain yield. Additionally, the B fertigation at 1.25 kg ha−1 was highly efficient in increasing the grain as well as stover yield exhibiting values of 13.6 q ha−1 and 133.9 q ha−1, respectively. The above treatment also led to the significant enhancement of B concentration and its uptake in grain and stover of pigeonpea. Economic analysis further confirmed the higher potential of B fertigation at 1.25 kg ha−1 on the basis of improved net return and B:C ratio as compared to the other soil treatments. Therefore, B fertigation at 1.25 kg ha−1 significantly improved the growth parameters, yield, B content as well as economic profit, which could be considered as the most efficient soil treatment for alleviating the B deficiency in pigeonpea.

The effect of pH on boron toxicity and nutrient uptake by wheat and rapeseed

Although boron (B) is essential micronutrient, higher soil B concentrations become toxic to the plants in arid and semi-arid regions of the world. Very little is known about the pH related nutrient solubility, including transpiration-mediated B uptake by plants. The effects of high B (200 μM) and low to high pH (3.0–10.0) on B toxicity, transpiration and nutrient uptake by wheat and rapeseed were studied. Plants were grown for 5 weeks under greenhouse conditions and analyzed for elements concentrations. Regardless of high B or not, low pH favored in the higher B accumulation in roots and shoots of both plant species. However, both plant species exhibited a differential B uptake pattern in roots and shoots. Both low and high pH levels in combination with high B decreased the plant biomass, transpiration, N and Mg concentrations, whereas increased the K, Ca, S, Cu, Fe, Mn and Zn concentrations. With the increase in pH 3.0–10.0, excess B decreased the Cl concentrations in wheat and rapeseed. In conclusion, low pH and high B supply enhanced the transpiration-assisted B uptake by plants although pH alone had little effects on B concentrations. Furthermore, nutritional disorder caused by high B in conjunction with low to high pH (3.0–10.0) inhibited the plant growth and transpiration.

Insight into the Root Transcriptome of a Boron-Tolerant Triticum zhukovskyi Genotype Grown under Boron Toxicity

Boron (B) toxicity is an important abiotic stress that drastically damages agricultural production worldwide, mostly in arid regions. Several studies have reported large losses in wheat due to high B in arable land. The identification of different B-toxicity-tolerant wheat germplasm and using them in breeding programs to develop tolerant cultivars is a potential solution to B toxicity. However, tolerance to B toxicity in such germplasm largely relies on the molecular changes in plants under B toxicity at the transcriptome level. Thus, the aim of this study is to determine the transcriptomic response of the roots of a B-toxicity-tolerant Triticum zhukovskyi genotype, PI296968, grown in a highly toxic B environment (10 mM B) in comparison with a control (3.1 μM B) treatment. T. zhukovskyi is a hexaploid wheat species forming a separate lineage from the main wheat lineage and can be a good source of genes for various stresses. However, it has been hardly explored for tolerance to any abiotic stress condition. This study is the first in the literature reporting the B toxicity tolerance of a T. zhukovskyi genotype along with the molecular changes occurring in it under B toxicity as compared to the control treatment. In the present study, 5992 genes were found to be significantly differentially expressed, with 1679 and 4313 up- and down-regulated genes, respectively. A number of transcription factors and pathways were identified to be significantly involved in the B toxicity response of the T. zhukovskyi genotype. A total of 12582 novel transcripts were determined in the study, with 9238 and 3344 coding and noncoding transcripts, respectively. The results not only suggest several candidate genes that can be further studied to improve wheat tolerance to B toxicity in upcoming breeding programs, but also enhance the understanding of the regulatory and molecular processes behind the wheat response to B toxicity. Further experiments are suggested to functionally characterize the identified high-B-responsive genes to confirm their role in providing B toxicity tolerance to the plants.

Salt Pretreatment-Mediated Alleviation of Boron Toxicity in Safflower Cultivars: Growth, Boron Accumulation, Photochemical Activities, Antioxidant Defense Response.

The study aims to elucidate alleviant effects of boron (B) toxicity by salt pretreatment (SP) on growth response, phytoremediation capacity, photosynthesis, and defense mechanisms in two safflower cultivars (Carthamus tinctorius L.; Dinçer and Remzibey-05). Eighteen-day-old plants were divided into two groups: SP (75 mM NaCl for 5 days) and/or B treatment (C, 2, 4, 6, and 8 mM B for 10 days). Depending on the applied B toxicity, B concentrations in roots and leaves of both cultivars, necrotic areas of leaves, ion leakage (RLR), and H2O2 synthesis increased, while shoot and root length as well as biomass, water, chlorophyll a+b, and carotenoid content decreased. In addition, chlorophyll a fluorescence results revealed that every stage of the light reactions of photosynthesis was adversely affected under B toxicity, resulting in decreases in performance indexes (PIABS and PITOT). However, the cultivars tended to induce the synthesis of anthocyanins and flavonoids and increase the activity of antioxidant enzymes (SOD, POD, APX, and GR) to detoxify reactive oxygen species (ROS) under B toxicity. SP mitigated the negative effects of toxic B on biomass, water and pigment content, membrane integrity, photosynthetic activity, and defense systems. Considering all results, Remzibey-05 was able to better overcome the biochemical and physiological changes that may be caused by B toxicity by more effectively rendering B harmless, although it accumulated more B than Dinçer.

The Effects of Salinity and B Toxicity on Some Soil and Plant Parameters

Ensuring the continuity of species that can grow naturally and increasing their availability without causing an economic burden in soils with salinity and boron toxicity has become an increasingly important worldwide issue. For this purpose, the effects of the Limonium gmelinii treated with NaCl, Na₂SO₄ to be grown on saline and boron toxicity areas with their respective plant and salt content, soil reaction and exchangeable Ca, Mg, K and N contents were investigated. The effect of the treatments on the increase of EC content in soil and plant was found to be significant. It also had an effect on the increase in the pH value of the soil. The effect of the decrease in the exchangeable Mg content in the soil and the increase in the Mg content in the plant was found to be significant. Moreover, while its effect on the decrease in Ca content in the soil was significant, it did not affect the Ca content in the plant. Its effect on the decrease in K content in the soil was found to be significant, but it did not affect the K content in the plant. Furthermore, the effect of treatments on N content in soil was found to be significant. It was observed that Limonium gmelinii can be grown in areas with NaCl, Na₂SO₄ and B toxicity without significant damage. Economic income can be obtained by determining the different post-harvest uses of the Limonium gmelinii plant, which is tolerant to such problem areas. Dried flowers can be used for decoration. In addition to the economic income to be obtained by growing it on unused and idle lands due to salinity and B toxicity problems, it can also offer a beautiful landscape with its green leaves and blue flowers in summer and winter seasons.

Effect of boron toxicity on pollen tube cell wall architecture and the relationship of cell wall components of Castanea mollissima Blume.

Boron (B) is essential to plant development. However, excessive B is toxic to plants. This research was performed to evaluate the effects of B toxicity on cell wall architecture of Chinese chestnut (Castanea mollissima Blume) pollen tubes with emphasis on the relationship among pectins, cellulose, and callose. Results showed that 0.8 mM H3BO3 inhibited pollen germination and led to abnormal morphology of the pollen tubes. B toxicity also affected the distribution of cell wall components of the pollen tube. In control pollen tube, esterified and acid pectins were distributed unevenly, with the former mainly at the tip and the latter on the distal region. Cellulose was distributed uniformly on the surface with less at the tip; callose reduced gradually from base to sub-tip of the pollen tubes and no callose at the tip of the tube was detected. B toxicity led to the deposition of esterified and acid pectins, cellulose, and callose at the tip of the pollen tube. Results from scanning electron microscopy and transmission electron microscopy showed that B toxicity also altered pollen tube wall ultrastructure. The results from enzymatic treatment illustrated that there existed a close relationship among pectins, cellulose, and callose. B toxicity also altered the relationship. In a word, B toxicity altered deposition and relationship of pectins, cellulose, and callose of pollen tube wall.

Boron Toxicity in Rice Soils.

Boron Toxicity in Rice Soils.

Characterization of two Peruvian maize landraces differing in boron toxicity tolerance

Boron (B) toxicity is a major agricultural problem that causes a considerable decrease in crop yield and quality. The soil in arid and semi-arid areas is often subjected to excessive B content. Southwestern Perú (department of Tacna) is characterized by high B levels in its agricultural land and irrigation water. This work analyzes the response of two local maize (Zea mays) landraces (Pachía and Sama) from Tacna to B toxicity. Both landraces were, therefore, grown in hydroponic media under control and B toxicity conditions, and after 10 days, seedlings were harvested and B content, B-transporter gene expressions, and several morphological and physiological parameters were determined. The leaf and root soluble B content was lower in Sama than in Pachía when both landraces were subjected to high B concentrations, which could be explained by its higher expression levels of B-efflux transporters. The capacity of Sama to maintain reduced levels of soluble B in its leaves and roots led to decreased leaf damage and higher photosynthetic and growth parameters under B toxicity conditions. These results support the proposal that Sama would perform better than Pachía under excessive B conditions, thus making it a more suitable landrace to be used in soils with toxic levels of B.

The Effects of Boron Toxicity and Bacteria (PGPR) Applications on Growth Development and Physiological Properties in Medicinal Sage (Salvia officinalis L.)

Bu çalışmada; farklı rizobakteri (Azospirillum lipoferum, Bacillus megaterium ve Frateuria aurentia) ve bor dozlarının (0 mM, 5 mM, 10 mM ve 20 mM) tıbbi adaçayı (Salvia officinalisL.) bitkisinin fide gelişim parametreleri ile toplam flavonol ve klorofil miktarları, yaprak alanı ve sıcaklığı gibi fizyolojik özellikler üzerine etkilerini belirlemek amacıyla tam kontrollü iklim kabininde 2021 yılında yürütülmüştür. Deneme, Tesadüf Parselleri Deneme Deseni’ne göre faktöriyel düzende 4 tekerrürlü olarak kurulmuştur. Araştırmada, kök ve fide uzunluğu (cm), kök ve fide yaş ağırlığı (g), kök ve fide kuru ağırlığı (g) gibi büyüme ve gelişim parametreleri ile toplam flavonol ve klorofil içeriği (dualex değeri), yaprak alanı (cm2) ve sıcaklığı (oC) gibi fizyolojik parametreler incelenmiştir. Araştırma sonucunda; PGPR uygulamalarının kök uzunluğu, fide yaş ağırlığı, fide uzunluğu, kök yaş ve kuru ağırlığı ve yaprak alanı üzerindeki etkisi istatistiksel olarak önemli bulunurken, fide kuru ağırlığı, yaprak sıcaklığı, flavonol ve klorofil miktarı üzerine etkisi istatistiksel olarak önemsiz olmuştur. Rizobakteri uygulamaları ile büyüme parametrelerinde kontrole kıyasla önemli artışların olduğu kaydedilmiştir. Bor dozlarının yaprak sıcaklığı hariç, diğer parametreler üzerindeki etkisinin önemli olduğu tespit edilmiştir. Ayrıca, artan bor dozları ile büyüme parametrelerinde azalmaların olduğu, ancak, toplam flavonol ve klorofil içeriğinde ise artışların olduğu tespit edilmiştir.

Single and Mixture Toxicity of Boron and Vanadium Nanoparticles in the Soil Annelid Enchytraeus crypticus: A Multi-Biomarker Approach.

The increased use and production of new materials has contributed to Anthropocene biodiversity decrease. Therefore, a careful and effective toxicity evaluation of these new materials is crucial. However, environmental risk assessment is facing new challenges due to the specific characteristics of nanomaterials (NMs). Most of the available ecotoxicity studies target the aquatic ecosystems and single exposures of NMs. The present study evaluated Enchytraeus crypticus survival and reproduction (28 days) and biochemical responses (14 days) when exposed to nanoparticles of vanadium (VNPs) and boron (BNPs) (single and mixture; tested concentrations: 10 and 50 mg/kg). Although at the organism level the combined exposures (VNPs + BNPs) did not induce a different toxicity from the single exposures, the biochemical analysis revealed a more complex picture. VNPs presented a higher toxicity than BNPs. VNPs (50 mg/kg), independently of the presence of BNPs (additive or independent effects), caused a decrease in survival and reproduction. However, acetylcholinesterase, glutathione S-transferase, catalase, glutathione reductase activities, and lipid peroxidation levels revealed alterations in neurotoxicity, detoxification and antioxidant responses, depending on the time and type of exposure (single or mixture). The results from this study highlight different responses of the organisms to contaminants in single versus mixture exposures, mainly at the biochemical level.

Identifying Signal-Crosstalk Mechanism in Maize Plants during Combined Salinity and Boron Stress Using Integrative Systems Biology Approaches.

Combined stress has been seen as a major threat to world agriculture production. Maize is one of the leading cereal crops of the world due to its wide spectrum of growth conditions and is moderately sensitive to salt stress. A saline soil environment is a major factor that hinders its growth and overall yield and causes an increase in the concentration of micronutrients like boron, leading to excess over the requirement of the plant. Boron toxicity combined with salinity has been reported to be a serious threat to the yield and quality of maize. The response signatures of the maize plants to the combined effect of salinity and boron stress have not been studied well. We carried out an integrative systems-level analysis of the publicly available transcriptomic data generated on tolerant maize (Lluteño maize from the Atacama Desert, Chile) landrace under combined salt and boron stress. We identified significant biological processes that are differentially regulated in combined salt and boron stress in the leaves and roots of maize, respectively. Protein-protein interaction network analysis identified important roles of aldehyde dehydrogenase (ALDH), galactinol synthase 2 (GOLS2) proteins of leaf and proteolipid membrane potential regulator (pmpm4), metallothionein lea protein group 3 (mlg3), and cold regulated 410 (COR410) proteins of root in salt tolerance and regulating boron toxicity in maize. Identification of transcription factors coupled with regulatory network analysis using machine learning approach identified a few heat shock factors (HSFs) and NAC (NAM (no apical meristem, Petunia), ATAF1–2 (Arabidopsis thaliana activating factor), and CUC2 (cup-shaped cotyledon, Arabidopsis)) family transcription factors (TFs) to play crucial roles in salt tolerance, maintaining reactive oxygen species (ROS) levels and minimizing oxidative damage to the cells. These findings will provide new ways to design targeted functional validation experiments for developing multistress-resistant maize crops.

Assessment of Surface and Groundwater Quality and their Suitability for Irrigation Purposes in Odisha, Eastern India

The study was conducted during the pre-monsoon period in April-May 2019 to monitor the quality of different water sources for assessing their suitability for irrigation purposes in Odisha state of eastern India. Twenty-seven surface water and twenty-one groundwater samples were collected and analyzed for chemical parameters. The suitability of the surface and groundwater for irrigation were evaluated based on pH, residual sodium bicarbonate (RSBC), electrical conductivity (EC), sodium adsorption ratio (SAR), Adjusted SAR (Adj. SAR), residual sodium carbonate (RSC), soluble sodium percentage (SSP), permeability index (PI), Kelly’s ratio (KR), Chloride (Cl-), boron (B), nitrate (NO3-), iron (Fe), Manganese (Mn), zinc (Zn), copper (Cu), chromium (Cr) and cadmium (Cd). Results showed that three rivers, Mahanadi, Brahmani and Bansadhara, were found medium salinity (EC 0.25-0.75 dSm-1), and all the rivers have no sodicity problem with RSC within the permissible limit of 2.5 meqL-1 and free of chloride and boron toxicity. All the surface water samples were safe with respect to Zn (2 mgL-1), Cu (0.2 mgL-1), Fe (5 mgL-1), Mn (0.2 mgL-1) and Cr (0.1 mgL-1). Four rivers were exceeded the maximum permissible limit of Cd. All the groundwater samples were found below the toxicity level and safe concerning Cl-, NO3-, B, Zn (2 mgL-1), Cu (0.2 mgL-1), Fe (5 mgL-1), Mn (0.2 mgL-1) and Cr (0.1 mgL-1) where Cd content of three sources exceeded the MPL (OUAT Agronomy Farm 0.011 mgL-1, Putibandh of Sambalpur 0.011 mgL-1 and Rourkela 0.010 mgL-1). Results depicted that all the surface water samples collected from nine different rivers are of good quality and suitable for irrigation purpose except for some specific limitations. Among all the groundwater sources, groundwaters of the Putibandh area in Sambalpur district are found very poor in quality and unsuitable for irrigation.

Exogenous application of silicon alleviates boron toxicity in rice seedlings

Exogenous application of silicon alleviates boron toxicity in rice seedlings

Melatonin improves tolerance to salt stress and boron toxicity in soybean and pepper plants

The role of melatonin (MT) in promoting tolerance to salt stress and boron toxicity in soybean and pepper plants was investigated. The treatments comprised: Control (C), salt stress (SS; 100 mM NaCl), boron toxicity (BT; 2 mM B) and SS + BT. Harmful effects of combined stresses resulted in a greater decrease in plant biomass and chlorophyll contents in both plants compared to those of a single stress. However, SS and BT increased electron leakage, and contents of H2O2, proline and MDA, while an increase was observed in the activities of POD, SOD and CAT. Foliar applied MT (100 μM) caused an increase in fresh and dry mass and photosynthetic pigments of plants of both crops under both stresses imposed singly or in combination. However, melatonin reduced electron leakage, and the contents of H2O2 and MDA. Proline contents in the pepper plants increased with MT application, while they decreased in the soybean plants. The activities of vital antioxidant enzymes, POD, SOD and CAT were found to be increased with MT application in both plants.

The effect of 24-epibrassinolide on gene expression related to cell walls under boron deficiency and toxicity in the leaves of Arabidopsis thaliana

The changing composition of plant cell walls allows for the continuation of the existing structure under normal conditions and also the protection of physical integrity under altering environmental conditions. In this study, the possible effects of the 24-Epibrassinolide (EBL) hormone under boron (B) deficiency and toxicity conditions on the expression of cell wall-related genes [cellulose synthase (CESA), expansin (EXP), xyloglucan endotransglucosylase/hydrolase (XTH) and pectin methylesterase (PME)] were investigated in the rosette leaves of Arabidopsis thaliana. For this purpose, 0 or 3000 ?M of boric acid (BA) and/or 1 ?M of EBL were applied to the plants which were grown in a hydroponic medium for five and ten weeks. While B-toxicity elevated the mRNA levels of the CESA4 and CESA8 genes in the leaves of the five-week-old plants, B-stress (B-deficiency and -toxicity) caused an increase in the expression of the CESA4, CESA6, and CESA8 genes in the ten-week-old plants. The transcript levels of the EXPA5 gene increased under B-stress in the ten-week-old plants whereas the expression of the EXPA8 gene decreased when compared to the control at two developmental stages. Co-treatment of EBL and B-stress strongly elevated the transcript level of the EXPA5 gene in the ten-week-old plants and the EXPA8 gene at both developmental stages. The EXPA14 and XTH23 genes exhibited distinct expression profiles under B-deficiency and -toxicity in both the five- and ten-week-old plants. The transcript level of the XTH21 gene was upregulated in the leaves of the plants exposed to B-stress. The mRNA level of the PME2 and PME41 genes was generally upregulated in response to B-stress in both the five- and ten-week-old plants. 24-Epibrassinolide alone and in combination with B-stress led to a remarkable increase in the expression of the XTH and PME genes compared to the control. These results demonstrate that cell wall genes generally show a similar pattern of expression at both developmental stages and the EBL hormone induces changes in the expression levels of cell wall-related genes under B-stress.

THE AVAILABILITY STATUS OF BORON IN THE CULTIVATED SOIL OF NEPAL

Boron is available in nature in rocks and deposits and the availability is influenced by soil organic matter, soil pH, soil texture, and temperature and is taken up by plants in non-ionic form H3BO3 (boric acid) but this concentration account for only about 10% of total soil boron leading to boron deficiency. Also, boron toxicity may occur in low rainfall, extremely alkaline, and saline soils harming plants’ growth and development. Boron shortage and toxicity in plants have a fairly narrow range, and both are detrimental. Hence, it is needed to critically balance boron homeostasis in cropping soil. The concentration of boron in cultivated soil in different agroecological regions was found to be low to very low (1mg/kg of soil) in this review study, which was undertaken to familiarize the status of boron in Nepalese cultivated land. In separate micronutrient investigations, a few additional micronutrients were shown to be medium albeit, boron was found to be low even in the valley (>0.01ppm) including all three ecological regions. This shows boron deficiency is a universal problem in Nepal affecting 80-90% of agricultural soil. And this problem can be corrected by both foliar applications and by soil application of boron sources such as borate as per the recommended dose.

Evaluation of Three New Citrus Rootstocks under Boron Toxicity Conditions

Boron (B) toxicity is a common limiting factor both in arid and semiarid regions, such as the Mediterranean Basin. Citrus trees are sensitive to B-toxicity, which generates a negative impact in citrus orchards. In this work, two promising citrus rootstocks (UFR-6 and 2247 x 6070-02-2) have been assessed against B-toxicity and compared with Carrizo citrange, a common commercial citrus rootstock in Mediterranean Basin. Three B concentration treatments (Control, 1 and 2.5 mM H3BO3) were established, irrigating the plants three times per week for 21 days under greenhouse conditions. During the assay, above-ground symptoms, and chlorophyll index (SPAD) were recorded. At the end of the experiment, stomatal conductance, relative water content, and B concentration in leaves and roots were determined. The increasing B concentration in plants generates visual damage in leaves for all citrus rootstocks assayed. Carrizo citrange displayed the greatest visual symptoms, decreased its chlorophyll index (SPAD), and stomatal conductance throughout the B-treatment. However, UFR-6 and 2247 x 6070-02-2 displayed less symptoms than Carrizo citrange and only reduced its parameters under the 2.5 mM H3BO3 treatment. These results can aid citrus grower rootstock planting decisions with under B-toxicity conditions.

Selenium supplementation mitigates boron toxicity induced growth inhibition and oxidative damage in pepper plants

Selenium (Se) supplementation has been shown to attenuate the detrimental effects of abiotic stress conditions, such as salinity and drought on plant growth and development. However, little is known about Se-related responses in plants exposed to boron (B) toxicity. In this study, we aimed to evaluate the effects of Se supplementation on growth, B content, photosynthetic pigment concentrations, compatible solutes content, oxidative damage, and antioxidant capacity in pepper plants grown under low and high B stress. In order to achieve this objective, 26 day-old pepper plants were treated with different concentrations of boric acid (2 and 4 mM) and/or sodium selenate (10 and 20 µM) for 14 days. Our results show that both low and high B stress cause growth inhibition and oxidative injury in pepper. Furthermore, B stress resulted in significant increases in APX, POD, and SOD activities as well as in proline, reducing sugar, and total sugar contents at both levels. Lastly, a marked decrease was observed in photosynthetic pigment and total flavonoid contents in pepper leaves subjected to B toxicity. Se application at 10 µM alleviated low B stress-induced growth inhibition and lipid peroxidation by decreasing B accumulation and enhancing chlorophyll content in pepper. In addition, Se supplementation decreased the accumulation of soluble sugar and proline in B-treated pepper leaves. In conclusion, our findings reveal that Se application is protective against the adverse effects of B toxicity on growth and oxidative metabolism in pepper.

Exogenous calcium reduces boron toxicity by regulating efficient antioxidant system and boron forms in trifoliate rootstock

Boron (B) toxicity is a major limiting factor for crop production, and calcium (Ca) has been reported to alleviate B toxicity. However, mechanisms of Ca alleviating B toxicity in trifoliate rootstock are not clear. Therefore, the present investigation was conducted on trifoliate seedlings to explore the underneath mechanisms. We included two B (10 and 100 µM) and three Ca levels (0, 1.23 and 2.46 mM) to explore the effect of supplementary Ca supply on mitigating B toxicity in order to gain a better understanding of tolerance mechanism in citrus production. The results showed that Ca (2.46 mM) application significantly increased root dry weight and fresh weight by 32.26% and 24.60% under B toxicity condition, respectively. Meanwhile, the root growth was improved with a greater proportion of new roots. The supply of Ca did not reduce the total absorption of B, however, lowered the R-value of B and reduced its utilization efficiency in cell walls. Moreover, Ca also triggered the antioxidant enzyme system to scavenge reactive oxygen species and reduced malondialdehyde content. Nevertheless, total soluble protein did not show any significant effect. Taken together it could be concluded that Ca application can mitigate B toxicity by maintaining antioxidant enzyme system and free B concentration, thereby reducing the utilization efficiency of B in cell wall for avoiding excessive accumulation of B in cells.

Effect of bacteria and melatonin application on soil microbial activity on soybean plants grown under salt stress and boron toxicity conditions

Bu çalışmada, tuz stresi (TS) ve bor toksisitesi (BT) şartlarında soya bitkisine yapraktan yapılan melatonin (MT) uygulaması ve tohumdan bakteri aşılamasının bitki gelişimi ile topraktaki bazı mikrobiyal aktivitelere etkisi araştırılmıştır. Bu araştırma sera denemesi olarak toprak ortamında saksılarda yürütülmüştür. Araştırma konuları; kontrol, TS (100mM NaCl), BT (2mM B) ve TS+BT (100mM NaCl+2mM B) olarak belirlenmiştir. Araştırma sonuçlarına göre, soya bitkisinde en fazla zarar TS+BT birlikte uygulamasında görülmüştür. Genel olarak yapılan stres uygulamaları bitki yaş ve kuru ağırlıklarında ve DHA, MBC ve CO2 gibi toprak mikrobiyal aktivite içeriklerinde önemli azalmaya neden olmaktadır. Bunun yanı sıra, stres etkilerine karşı yapılan uygulamalardan özellikle bakteri aşılaması (BA) stresin etkilerini hafifletmede etkili olduğu belirlenmiştir. Bununla birlikte yapılan melatonin (MT) uygulaması ise, tek başına BA uygulaması kadar etkili olmamış fakat BA ile stres etkilerini daha fazla azaltmada destek görevi görmüştür. Yapılan BA ve MT uygulamaları ile soya bitkisinde, bitki yaş ve kuru ağırlıklarında ve toprak mikrobiyal aktivitelerinde (DHA, MBC ve CO2) artışlar olduğu tespit edilmiş ve bu artışlar istatistiki (P≤0.05) olarak önemli bulunmuştur.