Enriched biochars with silicon and calcium nanoparticles mitigated salt toxicity and improved safflower plant performance.

Modifying biochar with nano-nutrients is one of the most effective methods in improving the efficiency of biochar in reducing the adverse effects of environmental stresses such as salinity on plant growth and productivity. The possible effects of solid biochar, nano-silicon dioxide enriched biochar, nano-calcium carbonate enriched biochar, and combined application of these enriched biochars on physiological performance of safflower (Carthamus tinctorius L.) were evaluated under different levels of salt stress (non-saline, 6 and 12 dSm-1). Salt stress increased sodium content, reactive oxygen species generation, and antioxidant enzymes activity, but decreased potassium, calcium, magnesium, iron, zinc, silicon, photosynthetic pigments, leaf water content, and seed yield (by about 36%) of safflower plants. The addition of biochar forms to the saline soil improved growth (up to 24.6%) and seed yield (up to 37%) of safflower by reducing sodium accumulation (by about 32%) and ROS generation and enhancing nutrient uptake, photosynthetic pigments, and water contents of leaves. The combined forms of enriched biochars were the best treatment on reducing salt stress effects on safflower plants. Therefore, application of enriched biochars has a high potential to reduce the harmful effects of salt stress on plants.

Enriching biochar with calcium and silicon nanoparticles is a practical method to improve the ability of biochar to adsorb and immobilize harmful elements such as sodium in the rhizosphere. This enrichment enhanced safflower plant growth and physiological efficiency under salt stress by reducing sodium absorption and increasing the availability of beneficial nutrients.

Biochar-based nutritional nanocomposites: a superior treatment for alleviating salt toxicity and improving physiological performance of dill (Anethum graveolens).

Biochar-supported metal oxide nanocomposites as functional materials could help to improve the production and stress tolerance of plants by enhancing the physicochemical properties of biochar. This experiment was carried out to assess the effects of unmodified biochar (30 g kg-1 soil) and biochar-based nanocomposites (BNCs) of iron (30 g BNC-FeO kg-1 soil), zinc (30 g BNC-ZnO kg-1 soil), and a combined form (15 g BNC-FeO + 15 g BNC-ZnO kg-1 soil) on dill (Anethum graveolens L.) plants under various salinity levels (non-saline, 6 and 12 dS m-1). The biochar-related treatments reduced sodium content of the plants, leading to a decline in osmolytes, antioxidant enzymes activities, reactive oxygen species (ROS), lipid peroxidation, NADP reduction, abscisic acid, jasmonic acid, and salicylic acid in dill leaf tissues. The combined form of BNCs reduced sodium content of leaf tissue by about 22% and 26% under 6 and 12 dS m-1 salinities, respectively. In contrast, addition of biochar, particularly biochar-based nanocomposites to the saline soil, enhanced potassium, iron, and zinc contents of leaf tissue, photosynthetic pigments, leaf water content, oxygen evolution rate, hill reaction and ATPase activities, endogenous indole-3-acetic acid, plant organs biomass, and consequently essential oil yield of plant organs. The combined form of BNCs in comparison with unmodified biochar improved vegetative, inflorescence, and seed biomass under 12 dS m-1 salinity by about 33%, 25%, and 6%, respectively. These findings revealed that BNCs with novel structure can potentially enhance salt tolerance, plant biomass, and essential oil yield of different organs in salt-stressed dill plants through decreasing leaf sodium content and ROS generation and increasing nutrient availability, water status, and photosynthetic pigments.

Improving ATPase and PPase activities, nutrient uptake and growth of salt stressed ajowan plants by salicylic acid and iron-oxide nanoparticles.

KEY MESSAGE: Salicylic acid and iron-oxide nanoparticles alleviated salt toxicity and improved plant growth by stimulating the activities of H+-ATPase and H+-PPase and preventing nutrient imbalance. Two factorial experiments were undertaken in a greenhouse during 2018 and 2019, to evaluate the impacts of SA (1 mM) and nano-Fe2O3 (3 mM) sprays at 7 leaves and flowering stages on vacuolar H+-pumps, growth and essential oil of salt-subjected (0, 4, 8 and 12 dS m-1 NaCl) ajowan plants. Measurements of plant traits were started at about 12 days after the last foliar spray and continued up to maturity. The H+-ATPase and H+-PPase activities and root ATP content were enhanced under low salinity, but higher salinities reduced these parameters. Rising salinity enhanced Na uptake and translocation, endogenous SA and DPPH activity, while reduced K+/Na+ ratio and nutrients uptake, leading to a reduction in plant biomass. Treatment with SA, nano-Fe2O3 and their combination improved H+-pumps activities and ATP content in roots and leaves. The SA-related treatments caused the highest activities of H+-pumps in roots, but Fe-related treatments resulted in the highest activities of these pumps in leaves. Increasing H+-pumps activities reduced sodium uptake and translocation and enhanced nutrients uptake. Foliar treatments, especially SA + nano-Fe2O3 augmented endogenous SA, DPPH activity, and plant growth in salt-stressed plants. Essential oil contents of vegetative and inflorescence organs under severe salinity and seeds under moderate and severe salinities were enhanced. Maximum essential oil was obtained from seeds of SA + nano-Fe2O3-treated plants, which was strongly correlated with endogenous SA and DPPH. Nevertheless, the SA + nano-Fe2O3 was the best treatment for diminishing salt toxicity and improving ajowan plant growth and essential oil production.

Changes in soil properties and salt tolerance of safflower in response to biochar-based metal oxide nanocomposites of magnesium and manganese.

This original research was performed to assess the possible effects of solid biochar (25 g biochar kg-1 soil) and biochar-based nanocomposites (BNCs) of magnesium oxide (25 g BNC-MgO kg-1 soil), manganese oxide (25 g BNC-MnO biochar kg-1 soil) and combined use of these nanocomposites (12.5 g BNC-MgO + 12.5 g BNC-MnO kg-1 soil) on soil properties and salinity (non-saline, 6 and 12 dSm-1) tolerance of safflower plants (Carthamus tinctorius L.). Application of biochar, particularly BNCs increased the pH and cation exchange capacity of soil, and the contents of water, potassium, calcium, magnesium, manganese, chlorophyll (a & b), nutrients uptake, water use efficiency and plant growth. Sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) of soil, sodium absorption rate of plants and osmolyte production (soluble carbohydrates and proteins, proline and glycine betaine) under 6 and 12 dSm-1 salinities were decreased by biochar and BNCs treatments. Sodium sorption capacity of BNCs was much higher than the solid biochar, which reflected the superiority of BNCs in decreasing sodium uptake by plants. The combined application of BNC-MgO + BNC-MnO proved to be the preferable treatment for decreasing salt toxicity in safflower. Biochar and BNCs improved root and shoot growth by lowering SAR, ESP, sodium absorption rate of plants and osmotic stress under saline conditions. These results conclude that BNCs can enrich the plant cells with nutrients, increase the nutrients absorption rate and maintain the plant tissue water content at an optimum level to improve plant growth under salt stress.

How can biochar-based metal oxide nanocomposites counter salt toxicity in plants?

Application of biochar-based metal oxide nanocomposites can acquire new composites and combine the benefits of biochar with nanomaterials. For the first time, this research was conducted to evaluate the possible effects of solid biochar (25 g biochar kg-1 soil) and biochar-based nanocomposites (BNCs) of magnesium oxide (25 g BNC-MgO kg-1 soil), manganese oxide (25 g BNC-MnO biochar kg-1 soil) and combined use of these nanocomposites (12.5 g BNC-MgO + 12.5 g BNC-MnO kg-1 soil) on salt (non-saline, 6 and 12 dSm-1 NaCl salinities) tolerance of safflower plants (Carthamus tinctorius L.). Salinity reduced potassium, magnesium and manganese contents in root and leaf tissues, chlorophyll content index, photosynthetic pigments, maximum quantum yield of photosystem II (Fv/Fm) and relative photosynthetic electron transport rate (RETR), leaf water content and plant biomass, but increased the sodium content, reactive oxygen species generation (ROS), oxidative stress and antioxidants and ROS detoxification potential of safflower roots and leaves. Application of biochar and BNCs increased the contents of potassium, manganese and magnesium in plant tissues, photosynthetic pigments, Fv/Fm and RETR, leaf water content and reduced sodium accumulation, ROS generation and oxidative stress under saline conditions, leading to a higher plant biomass in comparison with control. The BNC-MgO + BNC-MnO was the superior treatment on reducing salt toxicity. This treatment reduced oxidative stress by enhancing photosynthetic pigments, Fv/Fm and RETR of safflower under salt stress. These results revealed that BNCs have a great potential for improving salt tolerance of plants through increasing RETR and decreasing sodium accumulation and ROS generation.

Foliar sprays of salicylic acid and jasmonic acid stimulate H+-ATPase activity of tonoplast, nutrient uptake and salt tolerance of soybean.

This research was conducted as factorial on the basis of randomized complete block design with three replications to evaluate the effects of salicylic acid (1 mM SA), jasmonic acid (0.5 mM JA) and SA+JA on H+-ATPase hydrolytic activity of tonoplast in soybean roots under 0, 4, 7 and 10 dS m-1 NaCl levels. The H+-ATPase hydrolytic activity of tonoplast was increased under 4 dS m-1, but with rising salinity up to 7 and 10 dS m-1, the activity of H+-ATPase and ATP content were decreased in root cells. Root growth, potassium, calcium, magnesium and iron contents in plant tissues were decreased, while sodium, manganese, zinc and copper contents were increased by salinity, leading to a reduction in chlorophyll content index (CCI), relative water content (RWC), plant biomass and grain yield of soybean. Treatment of plants with SA, JA and SA+JA improved H+-ATPase activity and ATP content in root cells. JA treatment also reduced root growth, thereby limited sodium uptake by roots and translocation to the shoots. Foliar spray of JA only increased magnesium and iron contents in plant tissues, with no significant effect on other cations. In contrast, SA and SA+JA improved root growth and enhanced most of the cations, CCI, RWC, plant biomass and consequently grain yield under different levels of salinity. The SA+JA was a superior treatment in diminishing the harmful effects of salinity on soybean plant performance, compared with individual application of these growth regulators.

How can salicylic acid and jasmonic acid mitigate salt toxicity in soybean plants?

This research was undertaken to assess the impact of 1mM salicylic acid (SA) and 0.5mM jasmonic acid (JA) on alleviation of oxidative, ionic and osmotic stresses of different levels of salinity (0, 4, 7, 10 dS m-1 NaCl, respectively). Salinity increased the contents of glycine betaine, proline, soluble sugars, proteins and the activities of peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, and the amount of malondialdehyde and sodium ion of soybean leaves, but decreased the leaf water content, membrane stability index, potassium and calcium ions, chlorophylls content, chlorophyll stability index, plant biomass and seed yield. Foliar spray of JA reduced Na+ entry to the cells, while enhancing the glycine betaine and soluble proteins content, antioxidant enzymes activity, membrane stability index and leaf water content. This treatment had no effect on potassium and the calcium ions content, chlorophyll contents, chlorophyll stability index, soluble sugars, plant biomass and seed yield. In contrast, SA enriched the leaf cells with potassium and calcium ions under different levels of salt stress and increased glycine betaine, soluble sugars, proteins, antioxidant enzymes, leaf water content, membrane stability index, chlorophyll content and chlorophyll stability index, but reduced proline content. These superiorities of SA treatment led to considerable improvement in plant biomass (10%) and seed yield (17%) of soybean.

Changes in photosynthetic pigments, osmolytes and antioxidants of Indian mustard by drought and exogenous polyamines.

A pot experiment was performed as factorial based on randomized complete block design with three replications, to assess the effects of 1 mM spermidine (SPD) and 1 mM putrescine (PUT) on Indian mustard (Brassica Juncea L.) under different levels of watering (100, 75, 50 and 25% of field capacity). Chlorophyll a and b contents decreased, but the ratio of Chl a/b and carotenoid content increased with decreasing water supply. Foliar sprays of polyamines improved chlorophylls a and b and carotenoid contents, while the ratio of Chl a/b was reduced by these growth regulators. Relative water content, glycine betaine, proteins and soluble sugars contents were increased, but proline content was decreased by exogenous polyamines under limited water supply. Antioxidant enzyme (POX, CAT, SOD and APX) activities were enhanced by drought stress and polyamine treatments. This resulted in lower electrolyte leakage and lipid peroxidation (less MDA) under stressful conditions. The present results indicate that exogenous polyamines such as putrescine and spermidine can alleviate some of the deleterious impacts of water limitation on Indian mustard.

Exogenous salicylic acid and cytokinin alter sugar accumulation, antioxidants and membrane stability of faba bean.

This research was conducted in a greenhouse to evaluate the effects of exogenous application of salicylic acid (SA) (1 mM) and 6-benzylaminopurine (BAP) (50 µM) on physiological performance of faba bean (Vicia faba) under different levels of NaCl salinity (0, 4, 8 and 12 dS/m). The experiment was arranged as factorial on the bases of randomized complete block design in three replications. Leaf Na+ content, root and leaf soluble sugars, antioxidant enzymes activities such as catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and lipid peroxidation increased, but K+, K+/Na+ and membrane stability index (MSI) decreased as a result of salt stress. However, foliar sprays of BAP and particularly SA reduced Na+ content and lipid peroxidation, while enhanced the K+ content, K+/Na+, soluble sugars, antioxidant enzymes activities and MSI under different levels of salinity. It was, therefore, concluded that exogenous application of these growth regulators (GR) can considerably improve salt tolerance and physiological performance of faba bean.

Biochar-based nanoparticles mitigated arsenic toxicity and improved physiological performance of basil via enhancing cation exchange capacity and ferric chelate reductase activity.

The modified biochars have positive effects in reducing heavy metal toxicity for plants. However, the mechanism and extent of these effects on mitigating arsenic toxicity and plant performance are not clear. Thus, a pot experiment was conducted as factorial to evaluate the potential of fresh and enriched biochars with potassium and magnesium nano-sulfates [potassium-enriched biochar (K-BC), magnesium-enriched biochar (Mg-BC) in individual and combined forms] on reducing arsenic toxicity (non-contamination, 50, and 100 mg NaAsO2 kg-1 soil) in basil plants. Biochar-related treatments reduced plant arsenic absorption rate (up to 24%), arsenic content of root (up to 38%) and shoot (up to 21%) and root tonoplast H+-ATPase activity (up to 30%). The fresh and particularly enriched biochars improved soil properties (pH, CEC, and available iron content), ferric chelate reductase activity, iron, potassium and magnesium contents of plant tissues, chlorophyll content index, photochemical efficiency of photosystem II, relative electron transport rate, leaf area, and basil growth (shoot and root dry weight). These results revealed that enriched biochars are useful soil amendments for improving physiological performance of plants via reducing heavy metal toxicity and enhancing cation exchange capacity, nutrient availability and ferric chelate reductase activity. Therefore, soil amendment by enriched biochars could be a sustainable solution for enhancing plant productivity in contaminated soils via mitigating environmental impacts. This is an environmentally friendly method for using the natural wastes to overcome the adverse effects of soil pollutants on medicinal plants.

Improving electrochemical characteristics of plant roots by biochar is an efficient mechanism in increasing cations uptake by plants.

Electrochemical properties of roots such as zeta potential and cation exchange capacity are important factors that play a critical role in the absorption of nutrients by plants. Adding biochar to the soil may improve the electrochemical properties of the roots and thereby increase absorption of nutrients by plants. Thus, this research was laid out under greenhouse condition to evaluate the possible effects of biochar addition to soil (25 g biochar kg-1 soil) on changing electrochemical properties of roots, nutrients absorption, and growth parameters of safflower (with a deep root system) and mint (with a shallow root system) plants. Biochar noticeably increased pH and cation exchange capacity of soil, safflower and mint growth, calcium, magnesium and iron contents in roots and maximum sorption capacity of these nutrients by plant roots. Electrochemical measurements reveled that biochar application increases negative charges on root surface area (by about 30% and 36% in safflower and mint roots, respectively), cation exchange capacity of roots and root activity in both plants. On the other hand, biochar reduced zeta potential in plant roots (more negative potential). Reduction of zeta potential by biochar application were about 31% and 42% in safflower and mint roots, respectively. The cation-exchange groups (hydroxycinnamic acid + carboxyl groups) were increased due to biochar treatment by about 30% in safflower and 32% in mint roots. As an annual plant with deep roots, safflower roots had more functional groups, cation exchange capacity and root activity than mint plant in both biochar and control conditions. Results of this research showed that biochar not only adjusts physicochemical properties of rhizosphere, but also improves electrochemical specification of plant roots via increasing number of functional groups on root cell walls, which enhances maximum sorption capability of plant roots.

Solid and modified biochars mitigate root cell lignification and improve nutrients uptake in mint plants under fluoride and cadmium stresses.

Lignification is a physiological process that reduces pollutants' entrance into plant root cells via blocking apoplastic pathways. The closure of apoplastic pathways can also decrease the nutrients' uptake by roots. Application of biochar as an efficient soil amendment might be useful in increasing nutrients influx into root cells by decreasing lignification. Therefore, this experiment was performed to examine the conceivable effects of biochar forms [solid and chemically altered biochars with H2O2, KOH and H3PO4 (25 g biochar forms kg-1 soil)] on modifying lignification process and nutrients uptake by mint (Mentha crispa L.) plants under toxicity of cadmium and fluoride. The biochar treatments boosted plant root growth and activity as well as the real content and maximum sorption capacity of Zn, Fe, Mg, and Ca under stressful conditions. In contrast, biochar treatments increased root cell viability and reduced fluoride and cadmium contents, and oxidative damages under stressful conditions. The biochar treatments decreased the activity of phenylalanine ammonia-lyase and peroxidase enzymes under toxic conditions, which led to a decrease in the contents of lignin and its monomers (p-hydroxybenzaldehyde, guaiacyl, and syringaldehyde) in the roots. Solid biochar was less effective than engineered biochars in reducing root cell lignification. Therefore, addition of biochar forms to the soil could be an effective way to reduce root cell lignification and enhance nutrients uptake by plants under cadmium and fluoride toxicities.

The biochar-based nanocomposites improve seedling emergence and growth of dill by changing phytohormones and sugar signaling under salinity.

Biochar-based nanocomposites (BNCs) with a high level of sodium sorption capacity may improve salinity tolerance and seedling establishment of dill. Thus, a pot experiment was conducted to evaluate the effects of solid biochar (30 g solid biochar kg-1 soil) and biochar-based nanocomposites of iron (BNC-FeO) and zinc (BNC-ZnO) in individual (30 g BNC kg-1 soil) and a combined form (15 g BNC-FeO + 15 g BNC-ZnO kg-1 soil) on dill seedling growth in different levels of salt stress (non-saline, 6 and 12 dSm-1). Salinity caused a decrease in emergence percentage and emergence rate of seedlings. Increasing salinity of soil up to 12 dSm-1 decreased the biomass of dill seedlings by about 77%. Application of biochar and particularly BNCs increased the content of potassium, calcium, magnesium, iron, and zinc, reducing and non-reducing sugars, total sugars, invertase and sucrose synthase activities, leaf water content, gibberellic acid, and indole-3-acetic acid in dill plants, leading to an improvement in seedling growth (shoot length, root length, and dry weight) under saline conditions. Sodium content was noticeably decreased by BNC treatments (9-21%), which reduced mean emergence rate and stress phytohormones such as abscisic acid (31-43%), jasmonic acid (21-42%), and salicylic acid (16-23%). Therefore, BNCs especially in combined form can potentially improve emergence and growth of dill seedlings under salt stress, through reducing sodium content and endogenous stress hormones, and enhancing sugars and growth promoting hormones.

The biochar-based nanocomposites influence the quantity, quality and antioxidant activity of essential oil in dill seeds under salt stress.

The essential oil content and composition of medicinal plants may be influenced by eco-friendly products for nutrient availability under abiotic stresses. This research was conducted to determine the effects of biochar (30 g kg-1 soil) and biochar-based nanocomposites (BNCs) of iron (30 g BNC-FeO kg-1 soil), zinc (30 g BNC-ZnO kg-1 soil), and their combined form (15 + 15 g) on dill (Anethum graveolens L.) under salinity levels (non-saline, 6 and 12 dS m-1). Application of biochar, particularly BNCs increased iron and zinc content and decreased sodium accumulation in leaf tissues. The seed essential oil content increased under high salinity. Salinity changed the values of major compounds in essential oil and induced the formation of compounds such as alpha,2-dimethylstyrene, cuminyl alcohol, p-cymene, and linalool. Biochar treatments especially BNCs with a higher production of monoterpenes increased the levels of limonene, carvone, apiol, and dillapioll. All extracts showed a considerable DPPH-inhibitory effect with application of BNCs under salinity. The maximum antioxidant activity was observed under high level of salinity with application of the combined form. Therefore, the combined form of nanocomposite was the best treatment to improve the content of basic commercial monoterpenes and consequently antioxidant activity of essential oil in salt-stressed dill plants.

A comprehensive study on essential oil compositions, antioxidant, anticholinesterase and antityrosinase activities of three Iranian Artemisia species.

Artemisia is one of the most diverse genera in the Asteraceae family. The genus is wildly distributed in Irano-Turanian habitats and includes 34 species in Iran. Here, for the first time the essential oil variability, antioxidants and anti-cholinesterase and anti-tyrosinase activities of extracts of three Artemisia species (A. tournefortiana, A. khorassanica, A. haussknechtii), from different regions of Iran were evaluated. Based on GC-MS analyses, 81.84% to 98.70% of the total oils were identified. Cluster analysis grouped the studied populations in three different chemotypes. The highest and the lowest essential oil contents were observed in A. khorassanica and A. haussknechtii species, respectively. Camphor, en-in-dicycloether, 1,8-cineole and (Z)-ß-farnesene were the dominant components of essential oil in investigated ecotypes. The results revealed that the total phenol content was higher in A. tournefortiana collected from Kerman and A. haussknechtii collected from Chaharmahal and Bakhtiari. However, the lowest phenol content was recorded for A. haussknechtii collected from Isfahan province. The highest flavonoids content was found in A. tournefortiana collected from West Azerbaijan and A. khorassanica collected from North Khorasan. The highest FRAP antioxidant activity was observed in A. tournefortiana (Kerman) and the lower amount was in A. haussknechtii collected from Kohgiluyeh and Boyer-Ahmad. The highest antioxidant activity by DPPH method was in A. khorassanica collected from South Khorasan and the lowest activity was in Isfahan's A. haussknechtii. The acetycholine esterase inhibitory activity was higher in A. tournefortiana collected from West Azerbaijan; and the lowest activity was in A. haussknechtii collected from Chaharmahal and Bakhtiari province. The highest tyrosinase inhibitory activity was in A. khorassanica collected from North Khorasan; and the lowest was in A. haussknechtii collected from Chaharmahal and Bakhtiari.

The modified biochars influence nutrient and osmotic statuses and hormonal signaling of mint plants under fluoride and cadmium toxicities.

Introduction: Chemically modified biochars are a new generation of biochars that have a great ability to absorb and stabilize environmental pollutants. In this research, the physiological performance of mint plants (Mentha crispa L.) under fluoride and cadmium toxicities and biochar treatments was evaluated. Methods: Four levels of soil toxicities including non-toxic, 600 mg NaF kg-1 soil, 60 mg Cd kg-1 soil, and 600 mg NaF kg-1 soil + 60 mg Cd kg-1 soil were applied. The biochar addition to the soil was 25 g kg-1 (non-biochar, solid biochar, H2O2, KOH, and H3PO4-modified biochars). Results: The results showed that the application of biochar and especially chemically modified biochars reduced fluoride (about 15-37%) and cadmium (30-52%) contents in mint leaves, while increased soil pH and cation exchange capacity (CEC), nitrogen (12-35%), phosphorus (16-59%), potassium (17-52%), calcium (19-47%), magnesium (28-77%), iron (37-114%), zinc (45-226%), photosynthetic pigments of leaves and plant biomass (about 10-25%) under toxic conditions. Discussion: The biochar-related treatments reduced the osmotic stress and osmolytes content (proline, soluble proteins, and carbohydrates) in plant leaves. Plant leaf water content was increased by solid and modified biochar, up to 8% in toxic conditions. Furthermore, these treatments reduced the production of stress hormones [abscisic acid (27-55%), salicylic acid (31-50%), and jasmonic acid (6-12%)], but increased indole-3-acetic acid (14-31%) in plants under fluoride and cadmium stresses. Chemically modified biochars reduced fluoride and cadmium contents of plant leaves by about 20% and 22%, respectively, compared to solid biochar. Conclusion: This result clearly shows the superiority of modified biochars in protecting plants from soil pollutants.

Application of growth promoting hormones alters the composition and antioxidant potential of dill essential oil under salt stress.

The performance of dill plant may be affected by adverse environments such as salinity. Thus, this research was designed to evaluate changes in chemical composition and antioxidant activity of seed essential oil of dill (Anethum graveolens L.) in response to salinity (0, 5, 10 and 15 dS/m) and 1 mM of each hormonal treatments (gibberellic acid, salicylic acid, and cytokinin). Salicylic acid (SA) reduced Na+ content of roots and leaves by 15.4%, 30.9% and 12.4%, 24.3%, but enhanced K+ content by 29.8%, 51.6% and 76.6%, 73.4% under moderate and severe salinities, respectively. Essential oil yield was enhanced with progressing seed filling, despite decreasing essential oil percentage. Percentage of essential oil was increased under low and moderate salinities. Hormonal treatments, particularly SA enhanced seed mass and essential oil percentage, leading to enhanced essential oil yield. The amounts of most constituents were enhanced under moderate salinity. Foliar spray of SA and CK (cytokinin) increased almost all essential oil components, except dill ether and dill apiole, while the GA3 (gibberellic acid) treatment reduced most of the constituents. The α-fenchol was only induced by salt stress. The ß-pinene, 1-terpineol, cryptone, oxypeucedanin hydrate, α-thujene and P-α-dimethylstyrene were also specifically synthesized in SA treated plants under salinity. The highest TPC (total phenolic content) and antioxidant activity were recorded for essential oil of SA treated plants at mass maturity under moderate salinity. In general, the SA spray was the most effective treatment for improving essential oil quantity and quality of dill plants.

Responses of ajowan (Trachyspermum ammi L.) to exogenous salicylic acid and iron oxide nanoparticles under salt stress.

This research with a factorial arrangement was undertaken to investigate physiological responses of ajowan plants to foliar treatment of salicylic acid (1 mM) and nano-Fe2O3 (3 mM) under various salinity levels (0, 4, 8, 12 dS m-1 NaCl, respectively). Rising salinity enhanced sodium and endogenous SA contents, soluble sugars, protein, glycine betaine, proline, antioxidant enzymes activities, ROS generation, and lipid peroxidation, while reduced potassium and iron contents, membrane stability index, leaf water content, leaf pigments, root and shoot biomasses, and seed yield. Application of particularly SA and SA+nano-Fe2O3 alleviated salt toxicity via enhancing K+ uptake, K+/Na+ ratio, Fe content, endogenous level of SA, the activities of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, and polyphenol oxidase), and most of the osmolytes. These changes were resulted in improving membrane stability index, leaf water content, leaf pigments, root and shoot growth, and finally seed yield of plants under moderate and severe salinities. Therefore, these treatments can additively enhance salt tolerance and physiological performance of ajowan through increasing antioxidant capacity, osmolytes, and photosynthetic pigments. Graphical Abstract .

Improving yield-related physiological characteristics of spring rapeseed by integrated fertilizer management under water deficit conditions.

Two separate field experiments were conducted in 2018 and 2019 as split-plot based on randomized complete block design with three replications to evaluate physiological responses of rapeseed to fertilization treatments (control, chemical fertilizer, inoculation of seeds with PGPR, vermicompost and combined fertilizers) under different irrigation levels (irrigation after 70,100, 130, and 160 mm evaporation). Water stress increased the activities of catalase, polyphenol oxidase, peroxidase and superoxide dismutase and the contents of proline, soluble sugars and malondialdehyde and also leaf temperature, but decreased membrane stability index, chlorophyll content, leaf water content, stomatal conductance and grain yield. Application of fertilizers particularly combined fertilizers decreased proline content and leaf temperature, but increased the antioxidant enzymes activities, soluble sugars, chlorophyll content, leaf water content, membrane stability index, and stomatal conductance under different irrigation intervals. These superiorities of fertilization treatments were led to considerable improvement in grain yield. The results revealed that the combined fertilizer application improved most of the physiological parameters. It was deducted that the application of combined fertilizers reduced chemical fertilizer by about 67% and alleviated the deleterious effects of water limitation on field performance of rapeseed.

Changes in antioxidants and leaf pigments of safflower (Carthamus tinctorius L.) affected by exogenous spermine under water deficit.

Water deficit is one of the most limiting factors for plant growth and production. Polyamines are osmo-active compounds and have important roles in plant resistance to water limitation. A pot experiment was undertaken in a greenhouse as factorial based on complete randomized block design with three replications to assess the physiological and biochemical responses of safflower to different levels of water supply (100% and 40% field capacity) and spermine (0, 40 and 60 µM). Ascorbate peroxidase and peroxidase activities (POX), malondialdehyde (MDA), hydrogen peroxide (H2O2), anthocyanins, soluble protein, soluble sugars and proline contents in shoots increased, while total phenols, flavonoids, and photosynthetic pigments significantly decreased due to water deficit. Foliar spray of spermine mitigated the adverse effects of water deficit by increasing the catalase, superoxide dismutase, POX activities, soluble proteins and photosynthetic pigments, and by decreasing MDA and H2O2 contents. Spermine could, therefore, play an important role in protecting photosynthetic system and cellular membranes during drought stress in safflower.