Root Potassium Research Articles

Salinity Stress Responses and Adaptation Mechanisms of Zygophyllum propinquum: A Comprehensive Study on Growth, Water Relations, Ion Balance, Photosynthesis, and Antioxidant Defense.

Zygophyllum propinquum (Decne.) is a leaf succulent C4 perennial found in arid saline areas of southern Pakistan and neighboring countries, where it is utilized as herbal medicine. This study investigated how growth, water relations, ion content, chlorophyll fluorescence, and antioxidant system of Z. propinquum change as salinity levels increase (0, 150, 300, 600, and 900 mM NaCl). Salinity increments inhibited total plant fresh weight, whereas dry weight remained constant at moderate salinity and decreased at high salinity. Leaf area, succulence, and relative water content decreased as salinity increased. Similarly, the sap osmotic potential of both roots and shoots declined as NaCl concentrations increased. Except for a transitory increase in roots at 300 mM NaCl, sodium concentrations in roots and shoots increased constitutively to more than five times higher under saline conditions than in non-saline controls. Root potassium increased briefly at 300 mM NaCl but did not respond to NaCl treatments in the leaf. Photosynthetic pigments increased with 300 and 600 mM NaCl compared to non-saline treatments, although carotenoids appeared unaffected by NaCl treatments. Except for very high NaCl concentration (900 mM), salinity showed no significant effect on the maximum efficiency of photosystem II photochemistry (Fv/Fm). Light response curves demonstrated reduced absolute (ETR*) and maximum electron transport rates (ETRmax) for the 600 and 900 mM NaCl treatments. The alpha (α), which indicates the maximum yield of photosynthesis, decreased with increasing NaCl concentrations, reaching its lowest at 900 mM NaCl. Non-photochemical quenching (NPQ) values were significantly higher under 150 and 300 mM NaCl treatments than under non-saline and higher NaCl treatments. Electrolyte leakage, malondialdehyde (MDA), and hydrogen peroxide (H2O2) peaked only at 900 mM NaCl. Superoxide dismutase and glutathione reductase activities and glutathione content in both roots and shoots increased progressively with increasing salinity. Hence, growth reduction under low to moderate (150-600 mM NaCl) salinity appeared to be an induced response, while high (900 mM NaCl) salinity was injurious.

Nutrient Stoichiometry and Tree Development: Insights from a 5-Year Study on Catalpa bungei Fertilization

Short-term fertilization may provide limited improvements in tree growth and demonstrate suboptimal fertilizer efficiency; however, its benefits often fall short of expectations. Unfortunately, research addressing the sustained impacts of prolonged fertilization (e.g., beyond five years) on trees’ developmental dynamics and productivity remains relatively scarce. This study focused on a 7-year-old Catalpa bungei plantation located in Jinan City, Shandong Province, China. The study employed two fertilization techniques: hole fertilization (HF) and integrated water and fertilizer application (WF), with a no-fertilization treatment serving as the control (CK). The findings revealed that the WF significantly enhanced stand productivity. When comparing the different treatments, the productivity of WF stands demonstrated a remarkable increase of 39.7% compared to HF stands and 55.1% compared to CK stands. After five years of fertilization, the stands treated with WF exhibited a significant increase in volume accumulation, reaching 112.36 m3·hm−2. Additionally, the productivity of these WF-fertilized stands achieved an impressive 41.75 m3·hm−2·a−1. Fertilization notably enhanced the nitrogen content in the leaves and fine roots of C. bungei, as well as the potassium content in the coarse roots. These nutrients were found to be more concentrated in the corresponding organs within the WF stands. Over the entire growth cycle, there was a substantial consumption of key nutrients, with leaf nitrogen, phosphorus, and potassium contents decreasing by 30.5%, 18.8%, and 47.3%, respectively. Similarly, the coarse root potassium and fine root phosphorus content decreased by 24.7% and 24.4%, respectively. The enhancement in leaf nitrogen content following fertilization significantly contributed to increases in tree height, breast height diameter (DBH), and individual tree volume. Similarly, the enrichment of potassium in the branches and coarse roots was associated with improvements in DBH and tree volume. To maximize forest stand productivity, the WF fertilization method demonstrated superior results compared to HF. Therefore, WF should be prioritized in future fertilization experiments for C. bungei.

Selenium increases antimony uptake in ramie (Boehmeria nivea L.) by enhancing the physiological, antioxidative, and ionomic mechanisms

Ramie (Boehmeria nivea L.) is a promising phytoremediation candidate due to its high tolerance and enrichment capacity for antimony (Sb). However, challenges arise as Sb accumulated mainly in roots, complicating soil extraction. Under severe Sb contamination, the growth of ramie may be inhibited. Strategies are needed to enhance Sb accumulation in ramie's aboveground parts and improve tolerance to Sb stress. Considering the beneficial effects of selenium (Se) on plant growth and enhancing resistance to abiotic stresses, this study aimed to investigate the potential use of Se in enhancing Sb uptake by ramie. We investigated the effects of Se (0.5, 1, 2, 5, or 10 μM) on ramie growth, Sb uptake and speciation, antioxidant responses, and ionomic profiling in ramie under 10 mg/L of SbIII or antimonate (SbV) stresses. Results revealed that the addition of 0.5 μM Se significantly increased shoot biomass by 75.73% under SbIII stress but showed minimal effects on shoot and root length in both SbIII and SbV treatments. Under SbIII stress, 2 μM Se significantly enhanced Sb concentrations by 48.42% in roots and 62.88% in leaves. In the case of SbV exposure, 10 μM Se increased Sb content in roots by 42.57%, and 1 μM Se led to a 91.74% increase in leaves. The speciation analysis suggested that Se promoted the oxidation of SbIII to less toxic SbV to mitigate Sb toxicity. Additionally, Se addition effectively minimized the excess reactive oxygen species produced by Sb exposure, with the lowest malondialdehyde (MDA) content at 0.5 μM Se under SbIII and 2 μM Se under SbV, by activating antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione peroxidase. Ionomic analysis revealed that Se helped in maintaining the homeostasis of certain nutrient elements, including magnesium, potassium (K), calcium (Ca), iron (Fe), and copper (Cu) in the SbIII-treated roots and K and manganese (Mg) in the SbV-treated roots. The results suggest that low concentrations of Se can be employed to enhance the phytoremediation of Sb-contaminated soils using ramie.

WRKY6 transcription factor modulates root potassium acquisition through promoting expression of AKT1 in Arabidopsis.

Potassium (K+), being an essential macronutrient in plants, plays a central role in many aspects. Root growth is highly plastic and is affected by many different abiotic stresses including nutrient deficiency. The Shaker-type K+ channel Arabidopsis (Arabidopsis thaliana) K+ Transporter 1 (AKT1) is responsible for K+ uptake under both low and high external K+ conditions. However, the upstream transcription factor of AKT1 is not clear. Here, we demonstrated that the WRKY6 transcription factor modulates root growth to low potassium (LK) stress in Arabidopsis. WRKY6 showed a quick response to LK stress and also to many other abiotic stress treatments. The two wrky6 T-DNA insertion mutants were highly sensitive to LK treatment, whose primary root lengths were much shorter, less biomass and lower K+ content in roots than those of wild-type plants, while WRKY6-overexpression lines showed opposite phenotypes. A further investigation showed that WRKY6 regulated the expression of the AKT1 gene via directly binding to the W-box elements in its promoter through EMSA and ChIP-qPCR assays. A dual luciferase reporter analysis further demonstrated that WRKY6 enhanced the transcription of AKT1. Genetic analysis further revealed that the overexpression of AKT1 greatly rescued the short root phenotype of the wrky6 mutant under LK stress, suggesting AKT1 is epistatic to WRKY6 in the control of LK response. Further transcriptome profiling suggested that WRKY6 modulates LK response through a complex regulatory network. Thus, this study unveils a transcription factor that modulates root growth under potassium deficiency conditions by affecting the potassium channel gene AKT1 expression.

Exogenous application of selenium on sunflower (Helianthus annuus L.) to enhance drought stress tolerance by morpho-physiological and biochemical adaptations.

Drought stress poses a significant obstacle to agricultural productivity, particularly in the case of oilseed crops such as sunflower (Helianthus annuus L.). Selenium (Se) is a fundamental micronutrient that has been recognized for its ability to enhance plant resilience in the face of various environmental stresses. The FH-770 sunflower variety was cultivated in pots subjected to three stress levels (100% FC, 75% FC, and 50% FC) and four Se application rates (0 ppm, 30 ppm, 60 ppm, and 90 ppm). This research aimed to investigate the effect of exogenously applied Se on morpho-physiological and biochemical attributes of sunflower to improve the drought tolerance. Foliar Se application significantly lowered H2O2 (hydrogen peroxide; ROS) (20.89%) accumulation that markedly improved glycine betaine (GB) (74.46%) and total soluble protein (Pro) (68.63%), improved the accumulation of ascorbic acid (AA) (25.51%), total phenolics (TP) (39.34%), flavonoids (Flv) (73.16%), and anthocyanin (Ant) (83.73%), and improved the activity of antioxidant system superoxide dismutase (SOD) (157.63%), peroxidase (POD) (100.20%), and catalase (CAT) (49.87%), which ultimately improved sunflower growth by 36.65% during drought stress. Supplemental Se significantly increased shoot Se content (93.86%) and improved calcium (Ca2+), potassium (K+), and sodium (Na+) ions in roots by 36.16%, 42.68%, and 63.40%, respectively. Selenium supplements at lower concentrations (60 and 90 ppm) promoted the growth, development, and biochemical attributes of sunflowers in controlled and water-deficient circumstances. However, selenium treatment improved photosynthetic efficiency, plant growth, enzymatic activities, osmoregulation, biochemical characteristics, and nutrient balance. The mechanisms and molecular processes through which Se induces these modifications need further investigation to be properly identified.

Modified biochar enhances soil fertility and nutrient uptake and yield of rice in mercury-contaminated soil

Biochar, as an emerging soil remediation technology, has gained substantial attention. However, the impact of modified biochar on soil fertility, nutrient uptake, and rice yield in mercury (Hg)-contaminated soil remains unclear. This study explores the influence of biochar on soil fertility, nutrient absorption, photosynthesis, and rice yield in Hg-contaminated soil. We analyzed soil physicochemical properties, nutrient distribution (nitrogen, phosphorus and potassium) in roots, stems, and leaves, as well as plant gas exchange traits and yield components to provide a comprehensive assessment. Two experiments were conducted using original biochar (BC), produced via direct combustion and rice husk cracking, along with six types of modified biochar [amino (BCNH2), epoxy (BCCH(O)CH), ethoxy (BCC2H5O), sulfhydryl (BCSH), selenium (BCSe) loaded, and chitosan (BCchitosan)]. These biochars were applied at four different concentrations (0.07 %, 0.14 %, 0.20 % and 0.35 %). Comparative analysis against the control revealed that the application of modified biochar, particularly BCNH2, BCC2H5O and BCSH, significantly enhanced soil organic matter and plant nutrients (total N, available P, available K). Furthermore, it promoted the uptake of N, P, and K by rice leaves. The biochar addition exhibited a positive impact on rice photosynthesis and yield within a specific range of concentrations. A comprehensive analysis indicates that soil fertility, photosynthesis, and rice yield were significantly enhanced when BCNH2, BCC2H5O, and BCSH were applied at 0.20 % under the study conditions. These findings advance our understanding of how biochar affects soil fertility, nutrient uptake, and rice yield, offering valuable insights for practical agricultural and environmental management in Hg-contaminated fields.

Coordination of Root Traits and Rhizosphere Microbial Community in Tea (Camellia sinensis L.) Plants under Drought and Rehydration

Soil drought and rehydration have an immense impact on plant physiology and productivity, whereas the response of plant–microbe interactions to varied water availability remains largely elusive. In this study, two tea (Camellia sinensis L.) cultivars, Longjing43 and Yingshuang, were subjected to drought followed by rehydration. Soil drought significantly induced the elongation of taproots in the Yingshuang cultivar after two weeks of drought. Moreover, the four-week drought significantly reduced the root dry mass and root nitrogen, phosphorus, and potassium concentrations in both tea cultivars. Two-week rehydration recovered the root potassium concentration in the two tea cultivars, revealing the rapid response of root potassium levels to water conditions. Drought and rehydration also resulted in shifts in rhizosphere microbial diversity. A four-week drought reduced microbial alpha diversity in Longjing43 but not in the Yingshuang cultivar, and rehydration was effective in restoring alpha diversity in Longjing43. The rhizosphere microbial community tended to recover to the initial stages after rehydration in Longjing43 but not in the other cultivar. In addition, 18 microbial genera were identified as the featured microbial taxa in response to varied water availability, and a rare genus Ignavibacterium was significantly increased in the Longjing43 cultivar by rehydration after a four-week drought. Furthermore, root nitrogen, phosphorus, potassium levels, and dry mass were positively correlated with the microbial alpha diversity, while the taproot length was negatively correlated, suggesting the crucial role of plant–microbe interactions in response to drought and rehydration. Moreover, the root phosphorus concentration and taproot length also had significant effects on microbial beta diversity, further confirming their effects on the community structure of the rhizosphere microbiome. Overall, this study provides insights into the effects of drought on plant–microbe interactions in the rhizosphere of tea plants. These findings are important for harnessing the roles of the tea rhizosphere microbiome under drought.

Vermicompost Improves Tomato Yield and Quality by Promoting Carbohydrate Transport to Fruit under Salt Stress

To explore the effect of vermicompost on the yield and quality of tomato cultivated in salty soil, we investigated the soil chemical properties, the yield, vitamin C, organic acid, soluble solids, and nitrate of fruit, photosynthesis, and carbohydrates of plants grown under various salt levels applied with the application of either commercial chemical fertilizers, cow manure, or vermicompost. Results showed that the tomato yield was not increased from the chemical fertilizer application, while there was an increase from the cow manure and vermicompost (increased 31.7% and 65.2%, respectively) under salt stress. Compared to no salt stress, the contents of vitamin C, organic acid, soluble solids, and nitrate increased 26.55%, 40.59%, 46.31%, and 35.08%, respectively, under salt stress (2 g NaCl·kg−1 soil). Compared with the Control, the application of chemical fertilizers failed to improve the sugar/acid ratio but increased nitrate content, while cow manure and vermicompost improved the sugar/acid ratio by 42.0% and 73.1%, respectively. Particularly, vermicompost increased vitamin C and reduced nitrate to the greatest extent among the different fertilizer treatments. The decrease in sodium (Na+) in the roots and leaves, increase in carbohydrates in fruit, and photosynthetic efficiency of leaves imply an amendment effect of vermicompost on salt stress. Moreover, vermicompost also facilitated the transit of carbohydrates from leaves to fruits by increasing the accumulation of nitrogen, phosphate, and potassium in fruits, leaves, and roots, while decreasing proline and soluble protein accumulation in leaves and roots. In conclusion, vermicompost could alleviate the adverse effect of salt stress and improve tomato yield and fruit quality by improving the photosynthetic capacity and promoting carbohydrate transport to fruit. The findings give a new perspective on the beneficial effect of vermicompost on tomato yield and quality.

Evaluation of the quantitative and qualitative characteristics of sugar beet cultivars in different sowing times and transplanting and direct-seeding systems

To study the characteristics of sugar beet cultivars in transplanting and direct-seeding systems on three different sowing times (March 29, April 8, and April 18), a split plot experiment based on randomized complete blocks in three replications was carried out in Miandoab and Bokan regions, Northwest of Iran in 2016. The results showed that the highest nitrogen content was observed between the two test locations in the Bukan area. Results showed that the low root sodium, alkalinity, and molasses content was recorded for transplanting system. The minimum content of root sodium, nitrogen, and molasses sugar was observed in the plants sown on March 29. The Dorotea cultivar showed the highest root yield, sugar yield, and white sugar yield and the lowest root nitrogen and molasses sugar content compared to Isabella and Ekbatan. The highest white sugar content, coefficient of sugar extraction, sugar yield, root yield, and white sugar yield were recorded in the transplanting system with the sowing time of March 29; however, the highest content of root potassium and sugar content was observed in the transplanting system sown on April 18. The highest root yield was observed in the Dorotea cultivar, with a sowing time of March 29. Among the locations in the cultivar and planting system interaction treatments, the highest sugar content was found in the Bukan area's Dorotea cultivar in the transplanting system. Finally, the highest sugar yield was related to the transplanting system on March 29 in the Bukan area. It can be stated that an early sowing time (March 29), transplanting, and Dorotea variety were identified as the most appropriate treatments to improve the economic traits of sugar beet.

Study on Distribution Characteristics of Mineral Nutrients in Fritillaria hubeiensis

The contents and correlation of various mineral elements in soil and roots, stems and leaves of Fritillaria hubeiensis were analyzed and evaluated to supply basis for diagnosis of soil mineral nutrition and rational fertilization of Fritillaria hubeiensis. The contents of Phosphorus, potassium, calcium, magnesium, iron, zinc, manganese and copper were tested by the inductively coupled plasma, and the results were analyzed by SPSS11.5 software. The total contents of manganese, phosphorus, potassium, calcium and magnesium in soil and roots, leaves and stems of Fritillaria hubeiensis were different with different cultivation bases. The order of Fe and Cu contents was root > leaf > stem. The distribution of Zn showed a trend of “root > stem > leaf.” Between potassium content of soil and root, it was a significant positive correlation. But there was a significant negative correlation between Zinc content of soil and root. The total contents of calcium and iron were positively correlated between roots and stems. The total contents of Phosphorus, potassium, magnesium and copper were positively correlated among stems and leaves, while the contents of Mn were positively correlated. Therefore, Fritillaria hubeiensis mainly regulates the amount of mineral nutrients through selective absorption.

Levels of elements in selected food substances that support usage in the management and treatment of erectile dysfunction.

The use of fruits and vegetables for the management and treatment of erectile dysfunction has gained popularity due to the cheaper cost, accessibility and perceived absence of side effects. Much of the work done on plant-based aphrodisiacs has focused on the phytochemistry of secondary metabolites. This work sought to analyze selected fruits and vegetables that are commonly used in the management of erectile dysfunction in Ghana and quantify the levels of some micro- and macro-elements necessary for good penile health in order to determine the usefulness or otherwise of the selected produce. Energy-dispersive X-ray fluorescence spectroscopy was used to detect and quantify the levels of potassium (K), calcium (Ca), selenium (Se), magnesium (Mg), iron (Fe), and zinc (Zn) in carrot roots, cucumber fruit, garlic bulb, ginger rhizome, nutmeg fruit, sweet potato tuber, tiger nut tuber and watermelon fruit. The analysis revealed the presence of K, Ca, Mg, Fe and Zn. Levels of Se were below detection. The concentration of K was the highest in each of the food substances. However, in terms of recommended daily allowance, Mg had the highest contribution. Cucumber fruit and the rind of watermelon fruit had the highest levels of micro- and macro-elements implicated in erectile dysfunction. The potential use of these foods to treat and manage erectile dysfunction may not only be due to the presence of phytochemicals alone but also the presence of significant levels of micro- and macro-elements required for good penile health.

Plant Growth Promoting Bacteria and Arbuscular Mycorrhizae Improve the Growth of Persea americana var. Zutano under Salt Stress Conditions

In Peru, almost 50% of the national agricultural products come from the coast, highlighting the production of avocado. Much of this area has saline soils. Beneficial microorganisms can favorably contribute to mitigating the effect of salinity on crops. Two trials were carried out with var. Zutano to evaluate the role of native rhizobacteria and two Glomeromycota fungi, one from a fallow (GFI) and the other from a saline soil (GWI), in mitigating salinity in avocado: (i) the effect of plant growth promoting rhizobacteria, and (ii) the effect of inoculation with mycorrhizal fungi on salt stress tolerance. Rhizobacteria P. plecoglissicida, and B. subtilis contributed to decrease the accumulation of chlorine, potassium and sodium in roots, compared to the uninoculated control, while contributing to the accumulation of potassium in the leaves. Mycorrhizae increased the accumulation of sodium, potassium, and chlorine ions in the leaves at a low saline level. GWI decreased the accumulation of sodium in the leaves compared to the control (1.5 g NaCl without mycorrhizae) and was more efficient than GFI in increasing the accumulation of potassium in leaves and reducing chlorine root accumulation. The beneficial microorganisms tested are promising in the mitigation of salt stress in avocado.

The Role of Nanosilica in Ameliorating the Deleterious Effect of Salinity Shock on Cucumber Growth

A greenhouse experiment was conducted ‎to study the influence of the application of four concentrations of silica nanoparticles (NSi) in mitigating the negative effect of salinity shock on ‎cucumber (Cucumis sativus L.). Seedlings were sprayed with NSi ‎ (0, 100, 200, and 300 ppm) as the NSi treatment, and the plants were subjected to either no salinity shock (NSCh) or salinity shock (WSCh) 3250 ppm for two days. Yield and vegetative parameters, K+, Na+, K/Na ratio, Si, and proline contents were measured. The NSi treatments prevented the harmful effects of salinity on yield, with a reduction of 9.19% for plants treated with NSi3 under WSCh compared with NSCh. Salinity shock caused an accumulation of proline in the roots and other plant parts as a method of protection. The NSi2 and NSi3 treatments under WSCh prevented the accumulation of Na+, leading to an increase in the K/Na ratio. The Si contents in the roots, leaves, and fruits increased with increased NSi. The results of the interaction treatments showed a significant ‎effect on all ‎traits except for plant length, leaf area, chlorophyll, and ‎root ‎potassium content.

Characterization of phosphate transporter genes and the function of SgPT1 involved in phosphate uptake in Stylosanthes guianensis

Phosphorus (P) is one of the principal macronutrients for plant growth and productivity. Although the phosphate (Pi) transporter (PT) of the PHT1 family has been functionally characterized as participating in Pi uptake and transport in plants, information about PT genes in stylo (Stylosanthes guianensis), an important tropical forage legume that exhibits good adaptability to low-P acid soils, is limited. In this study, stylo root growth was found to be stimulated under P deficiency. The responses of PT genes to nutrient deficiencies and their roles in Pi uptake were further investigated in stylo. Four novel PT genes were identified in stylo and designated SgPT2 to SgPT5. Like SgPT1, which had been previously identified, all five SgPT proteins harboured the major facilitator superfamily (MFS) domain. Variations in tissue-specific expression were observed among the SgPT genes, which displayed diverse responses to deficiencies in nitrogen (N), P and potassium (K) in stylo roots. Four of the five SgPTs exhibited high levels of transcriptional responsiveness to P deficiency in roots. Furthermore, SgPT1, a Pi-starvation-induced gene closely related to legume PT homologues that participate in Pi transport, was selected for functional analysis. SgPT1 was localized to the plasma membrane. Analysis of transgenic Arabidopsis showed that overexpression of SgPT1 led to increased Pi accumulation and promoted root growth in Arabidopsis plants. Taken together, the results of this study suggest the involvement of SgPTs in the stylo response to nutrient deprivation. SgPT1 might mediate Pi uptake in stylo, which is beneficial for root growth during P deficiency.

Genome-wide transcriptome analysis of the orphan crop tef (Eragrostis tef (Zucc.) Trotter) under long-term low calcium stress

Calcium (Ca2+) is one of the essential mineral nutrients for plant growth and development. However, the effects of long-term Ca2+ deficiency in orphan crops such as Tef [(Eragrostis tef) (Zucc.) Trotter], which accumulate high levels of Ca in the grains, remained unknown. Tef is a staple crop for nearly 70 million people in East Africa, particularly in Ethiopia and Eritrea. It is one of the most nutrient-dense grains, and is also more resistant to marginal soils and climatic conditions than main cereals like corn, wheat, and rice. In this study, tef plants were grown in a hydroponic solution containing optimum (1 mM) or low (0.01 mM) Ca2+, and plant growth parameters and whole-genome transcriptome were analyzed. Ca+2-deficient plants exhibited leaf necrosis, leaf curling, and growth stunting symptoms. Ca2+ deficiency significantly decreased root and shoot Ca, potassium (K), and copper content in both root and shoots. At the same time, it greatly increased root iron (Fe) content, suggesting the role of Ca2+ in the uptake and/or translocation of these minerals. Transcriptomic analysis using RNA-seq revealed that members of Ca2+ channels, including the cyclic nucleotide-gated channels and glutamate receptor-like channels, Ca2+-transporters, Ca2+-binding proteins and Ca2+-dependent protein kinases were differentially regulated by Ca+2 treatment. Moreover, several Fe/metal transporters, including members of vacuolar Fe transporters, yellow stripe-like, natural resistance-associated macrophage protein, and oligo-peptide transporters, were differentially regulated between shoot and root in response to Ca2+ treatment. Taken together, our findings suggest that Ca2+ deficiency affects plant growth and mineral accumulation by regulating the transcriptomes of several transporters and signaling genes.

Arbuscular Mycorrhiza Alters Metal Uptake and the Physio-biochemical Responses of Glycyrrhiza glabra in aLead Contaminated Soil.

Arbuscular mycorrhizal (AM) fungi can affect the host’s ability to cope with several environmental stresses, such as heavy metal stress. Therefore, an experiment was conducted to assess the effect of the Funneliformis mosseae inoculation on growth and physio-biochemical parameters and lead (Pb) accumulation in liquorice (Glycyrrhiza glabra L.) under Pb stress. A factorial experiment was performed with the combination of two factors, fungi (inoculated and non-inoculated (NM)) and soil Pb levels (0, 150, 300, and 450 mg kg−1 soil) with four replicates. In the presence of Pb, symbiosis with F. mosseae exert positive effect on growth parameters, which was more significant in shoots than roots. Mycorrhization improved fresh and dry weights and length in shoot by 147, 112.5 and 83%, respectively, compared to NM plants at Pb150 level. Moreover, F. mosseae significantly increased tolerance index and the concentrations of soluble sugars and flavonoids in shoots and proline, phosphorus, potassium, calcium, zinc and manganese in shoots and roots but decreased their malondialdehyde concentrations under Pb stress. The Pb concentrations, transfer and bioaccumulation factors of mycorrhizal plants were less than non-mycorrhizal ones. A positive correlation was also observed between glomalin secretion and colonization rate in Pb treated soils. These results indicate the importance of mycorrhizal colonization in alleviating the Pb-induced stress in liquorice, mainly through improving the nutrition, modifying reactive oxygen species detoxifying metabolites and reducing the translocation of Pb to shoots. Observations revealed that mycorrhization of liquorice would be an efficient strategy to use in the phytoremediation practices of Pb-contaminated soils.

RESPONSE OF SUGAR BEET TO SANDY SOIL AMENDED BY ZEOLITE AND POTASSIUM SULFATE FERTILIZATION

Two field experiments were carried out on a private farm at Wadi El-Natrun (latitude of 30.48° N and longitude of 30.50° E), Beheira Governorate, Egypt, in the 2019–2020 and 2020–2021 seasons, to find out the effect of adding zeolite as a soil conditioner and potassium fertilizer on growth, yield, and quality of sugar beet crop (Beta vulgaris L. var. saccharifera) grown in sandy soil conditions. The present work included 12 treatments, which were the combinations of four zeolite levels (Zero, 476, 952, and 1,428 kg ha-1), and three levels of potassium in the form of potassium sulfate (119, 178.5, and 238 kg K2SO4 ha-1), which were added as a soil application. The treatments were arranged in a complete block design in a split plot with four replications. The results showed that higher values of the photosynthetic pigments, root diameter, fresh and foliage weights plant-1, as well as, sucrose and extracted sugar percentages, quality index, yields of the root, top, and sugar ha-1, were obtained by adding 1,428 kg zeolite, compared with the other levels of zeolite, in both seasons. However, sodium, alpha-amino N contents in the root, and sugar lost to molasses% were insignificantly affected by zeolite rates in both seasons. Application of 238 kg K2SO4 ha-1 significantly resulted in the highest values of photosynthetic pigments, root dimensions, sucrose%, and root potassium content. In addition, extracted sugar %, quality index, root, top, and sugar yields ha-1 were increased compared with the other lower K-sulphate levels in both seasons. On the contrary, sugar lost to molasses% was insignificantly affected by applied potassium sulfate in both seasons. The maximum values of root diameter, fresh weight, yields of root and top ha-1 in both seasons, and also sugar yield in the second season were produced from the interaction between applying 1,428 kg zeolite and 238 kg potassium sulfate ha1.

The Response of Three Mandarin Cultivars Grafted on Sour Orange Rootstock to Salinity Stress

ABSTRACT Citrus growth is often constrained by salinity, but citrus rootstocks respond to salinity differently. A greenhouse study was carried out in a completely randomized design with three cultivars of mandarin (‘Younesi,’ ‘Clementine,’ and ‘Yashar’) and four levels of salinity (control, 1, 3, and 5 dS/m) in three replications to explore the mechanism by which salinity stress affects photosynthetic and growth factors of mandarin cultivars. After applying salinity treatments, shoot fresh and dry weight, root fresh and dry weight, branch number, leaf number, plant height, leaf and root potassium (K), sodium (Na), and calcium (Ca) contents, chlorophyll content, proline content, leaf nitrogen, and protein content, electrolyte leakage, and sugar content were measured. The results showed that salinity stress reduced vegetative and photosynthetic factors in all three cultivars. Root and leaf K and Na contents, chlorophyll a, total chlorophyll, proline content, electrolyte leakage, and sugar and protein contents were affected by cultivars. Salinity affected root and leaf K and Na contents, chlorophyll a and b and total chlorophyll contents, proline, and electrolyte leakage significantly. The interaction of cultivar and salinity was also significant on chlorophyll a and total chlorophyll contents, leaf N and protein contents, and electrolyte leakage. Salinity stress reduced vegetative and photosynthesis factors of all three cultivars.

Effects of Phytohormone-Producing Rhizobacteria on Casparian Band Formation, Ion Homeostasis and Salt Tolerance of Durum Wheat

Inoculation with plant growth-promoting rhizobacteria can increase plant salt resistance. We aimed to reveal bacterial effects on the formation of apoplastic barriers and hormone concentration in relation to maintaining ion homeostasis and growth of salt-stressed plants. The rhizosphere of a durum wheat variety was inoculated with cytokinin-producing Bacillus subtilis and auxin-producing Pseudomonas mandelii strains. Plant growth, deposition of lignin and suberin and concentrations of sodium, potassium, phosphorus and hormones were studied in the plants exposed to salinity. Accumulation of sodium inhibited plant growth accompanied by a decline in potassium in roots and phosphorus in shoots of the salt-stressed plants. Inoculation with both bacterial strains resulted in faster appearance of Casparian bands in root endodermis and an increased growth of salt-stressed plants. B. subtilis prevented the decline in both potassium and phosphorus concentrations and increased concentration of cytokinins in salt-stressed plants. P. mandelii decreased the level of sodium accumulation and increased the concentration of auxin. Growth promotion was greater in plants inoculated with B. subtilis. Increased ion homeostasis may be related to the capacity of bacteria to accelerate the formation of Casparian bands preventing uncontrolled diffusion of solutes through the apoplast. We discuss the relative impacts of the decline in Na accumulation and maintenance of K and P content for growth improvement of salt-stressed plants and their possible relation to the changes in hormone concentration in plants.

Amino acids application alleviated salinity stress in spinach (Spinacia oleracea L.) by improving oxidative defense, osmolyte accumulation, and nutrient balance

Salinity is affecting more than 6 million hectares of cultivated area in Pakistan. The use of amino acids offers a pragmatic solution for minimizing the adverse effects of salinity on Spinacia oleracea L. (spinach). The present study evaluated the possible potential of amino acids in enhancing the salinity tolerance in spinach and identified the probable underlying mechanisms. The experiment comprised of two factors viz. amino acids with total of seven treatments; control, salinity (sal) 100 mM, Methionine + sal, Phenylalanine + sal, Proline + sal, Tyrosine + sal, Combined amino acids + sal, and two spinach cultivars (Desi Palak and VRI-2019). Salinity stress decreased the morpho-physiological attributes of both spinach cultivars, nevertheless, the application of combined amino acids effectively improved the tolerance against salinity stress. Compared with control, all applications of amino acids increased the root and shoot length, fresh and dry weight, number of leaves, and plant yield per plant of both spinach cultivars. However, the maximum was noted by the application of combined amino acids. Combined amino acids triggered the activities of antioxidants (catalase, superoxide dismutase, peroxidase), increased the contents of free proline, phenolics, flavonoids, chlorophyll a, b, carotenoids, calcium, and potassium in root and shoot while decreasing the reactive oxygen species (hydrogen peroxide) and sodium contents in both spinach cultivars under saline conditions. Overall, the VRI-2019 performed better than Desi Palak. The vigorous growth along with higher salinity tolerance because of amino acid treatments was linked to better chlorophyll contents, higher accumulation of osmolytes, maintenance of ionic balance, and an improved antioxidant defense system in Spinacia oleracea.