Ascorbic Acid Enhances Growth and Yield of Sweet Peppers (Capsicum annum) by Mitigating Salinity Stress

Salinity is a crucial problem which has affected crop productivity globally. Ascorbic acid is considered helpful against abiotic stresses due to its powerful antioxidant potential. In the pot experiment, salinity stress (0, 35, 70, and 105?mM) was applied to sweet peppers in split doses after 20 days of transplantation. To mitigate the adverse effects of salinity, ascorbic acid (0, 0.40, 0.80, and 1.20?mM) was applied as foliar spray after a 6-day interval during vegetative growth. Sweet pepper plants sprayed with distilled water (control) recorded maximum plant height (cm), leaf area (cm²), number of branches, stem diameter (mm), number of fruit plant^?1, fruit diameter (cm), yield plant^?1 (g), and chlorophyll content (mg 100?g^?1), while the maximum polyphenol oxidase (PPO) activity (unit mg protein^?1 min^?1) and ascorbate peroxidase (APX) activity (unit mg protein^?1 min^?1) were recorded in plants treated with 70?mM NaCl application. Salinity stress beyond 70?mM significantly reduced all the studied parameters. An ascorbic acid concentration of 1.20?mM significantly mitigated the negative effects of salt stress and recorded maximum plant height (cm), number of leaves plant^?1, leaf area (cm²), number of branches plant^?1, stem diameter (mm), number of fruit plant^?1, fruit diameter (cm), yield plant^?1 (g), chlorophyll content (mg 100?g^?1), PPO activity (unit mg protein^?1 min^?1), and APX activity (unit mg protein^?1 min^?1). Hence, a 1.20?mM concentration of foliar ascorbic acid could be used in saline conditions up to 70?mM of sodium chloride (NaCl) for better growth, productivity, and enzymatic activity of sweet peppers.

     

Physiological response of lupine and associated weeds grown at salt-affected soil to α‑tocopherol and hoeing treatments

About 900.000 ha of Egypt’s agricultural lands are suffering from salinity build-up problem. Therefore, two field experiments were conducted in split-split plot design with four replications to study α?tocopherols foliar application with 100 and 200 ppm and hand hoeing (two and three hand hoeing, plus unweeded) and their interactive effects on growth, osmoprotectants, mineral contents, seed yield, yield components, and nutritive value of the lupine plants and its associated weeds grown under salt-affected soil at 1.30, 3.20 and 4.23 dS m^?1. Three hand hoeing treatment achieved the highest weed depression expressed in the lowest number and dry matter of broad-leaved, narrow-leaved and total weeds, and reduction % in dry matter were 80.75, 78.25 and 79.26 % compared with unweeded, respectively. Salinity stress significantly decreased total chlorophyll content, leaf area index and plant dry weight, while α?tocopherol and hoeing increased in all previous traits relative to corresponding controls. Lupine seed yield, yield components, and oils, carbohydrates, proteins, carotenoids and alkaloids in the yielded seeds were significantly reduced by increasing salinity levels, meanwhile hoeing and α?tocopherol treatments improved them. Total essential amino acids were decreased by increasing salinity levels and increased by increasing α?tocopherol concentrations and number of hoeing treatments. It could be concluded that α?tocopherol especially at 200 ppm partially alleviated the harmful effects of salinity stress on the growth of lupine plants and nutritive value of the yielded seeds. Three hand hoeing treatment was the optimum and safe method in controlling weeds associated with lupine plant grown under salinity stress.     

Combined effects of salinity and phosphorus availability on growth,gas exchange,and nutrient status of Catapodium rigidum

The combined effects of NaCl-salinity and phosphorus deficiency on biomass production, nutritional status, and photosynthetic activity were studied in Catapodium rigidum: an annual Poacea with fodder potential. Plants were grown in hydroponic conditions for 55 days under two phosphorus (P) supply: 5 (low) or 180?µmol KH₂PO₄ (sufficient), in the absence or presence of 100?mM NaCl. Obtained results demonstrated that both salinity and P deficiency treatments applied separately reduced substantially plant growth and CO₂ assimilation rate with a more marked impact of salt stress. Salinity has no substantial effect on both shoot P concentrations and phosphorus acquisition efficiency independently of P availability. The highest decrease in plant growth (?91%) was observed in plants simultaneously submitted to both stresses suggesting an additive effect of the two stresses and that P deficiency increased the susceptibility of C. rigidum to salinity. This may be linked to a significant decrease in potassium acquisition (?95%), K/Na selectivity ratio (?73%), stomatal conductance (?66%), CO₂ assimilation rate (?64%), and shoot water content (66%). Furthermore, plants cultivated under combined salinity and sufficient P supply displayed higher stomatal conductance, CO₂ assimilation rate, K/Na selectivity ratio, and plant growth than plants cultivated under combined effects of salinity and P deficiency. These results suggest that adding P to saline soils could be an alternative for alleviating the negative effects of salinity and may ameliorate salinity tolerance.     

Effect of salinity on tissue nutrient contents of the four dryland tree species of Indus flood plains

Salinity is a common issue of semi-arid and arid lands rendering them unfit for agriculture. Saline wastelands can be converted into productive ecosystems by rehabilitating them with salt tolerant native tree species. The objective of this work was to study the effect of NaCl salinity on tissue nutrient contents of the four dryland tree species. Saplings were grown in pots under nonsaline and high salinity conditions. After eighteen weeks the plants were harvested and their tissue nutrient contents were analyzed. Results revealed that all species accumulated high amounts of Na⁺ under saline conditions, while concentrations of N, P and Mg²⁺ decreased in their tissues. Concentrations of K⁺ and Ca²⁺ showed more variable trend in various tissues in response to increase in soil salinity. Na⁺: K⁺ ratios of roots (1.57), stems (1.27), and leaves (1.66) of salinized Salvadora oleoides plants were lowest among all the four species. Root Na⁺: K⁺ ratio of salinized plants was significantly higher for Prosopis cineraria (7.10), while these ratios for stem (1.85) and leaf (3.42) were highest for Tamarix aphylla. Plants of P. cineraria showed lowest Stem-Na⁺/root-Na⁺ ratio (0.30) when subjected to salinity. Results showed that salinity induces nutrient deficiency in all species. Salinity tolerance of these species can be attributed to their ability to (i) restrict translocation of Na⁺ from roots to stem; (ii) keeping low tissue Na⁺: K⁺ ratios; and (iii) selectivity of K⁺ and Ca²⁺ over Na⁺, and can be used for the screening of salt-tolerant ecotypes for the rehabilitation of saline wastelands.     

Effects of Irrigation Water in Different Salinity on Yield and Quality Parameters of Tobacco (Nicotiana tabacum L.) Plant

Salinity affects many areas in our country and around the world, resulting in dramatic reductions in plant yields. In this study, the plant yield, some plant quality parameters, and soil salinity in the plant root area were investigated by irrigating tobacco plants (Nicotiana tabacum L.) with different salinity irrigation waters. The experiment was carried out in pots in 4 replicates according to the randomized plot design. Six different salinity of irrigation water applications were applied in the experiment (S0?=?0.38 dS m^?1, S1?=?2 dS m^?1, S2?=?5 dS m^?1, S3?=?8 dS m^?1, S4?=?11 dS m^?1, S5?=?15 dS m^?1). According to the data obtained at the end of the research, as the salinity of irrigation water increased, plant length, leaf width, leaf length, leaf dry weight and leaf number decreased. It was determined that there was a certain increase in nicotine content in the face of the decrease of all examined physical parameters in irrigation water increase. In addition, the salinity values in the plant root zone soils and the salinity values in the outlet (drainage) water have also increased. Salinity threshold value of the tobacco plant was determined to be 2.04 dS m^?1. With an increase in salinity by one unit, there was a 7.1% decrease in leaf dry weight. It was determined that the tobacco plant is vulnerable to salinity based on the data collected.

     

Contact and fumigant toxicity of plant essential oils and efficacy of spray formulations containing the oils against B‐ and Q‐biotypes of Bemisia tabaci

BACKGROUND: The contact + fumigant toxicity of 92 plant essential oils and control efficacy of 18 experimental spray formulations containing nine selected essential oils (0.5 and 0.1% sprays) and six commercial insecticides to females from B‐ and Q‐biotypes of Bemisia tabaci were evaluated using vapour‐phase mortality and spray bioassays. RESULTS: Garlic and oregano (LC₅₀, 0.15 mL cm^?3) were the most toxic oils against B‐ and Q‐biotype females. Strong fumigant toxicity to both biotype females was also obtained from catnip, cinnamon bark, clove bud, clove leaf, davana, savory and vetiver Haiti oils (LC₅₀, 0.17–0.48 mL cm^?3). The 0.5% sprays of these oils (except for thyme red oil) resulted in 90–100% mortality against both biotype females. Only garlic applied as 0.1% spray provided 100% mortality. Spinosad 100 g L^?1 suspension concentrate (SC) treatment resulted in 92 and 95% mortality against both biotype females, whereas acetamiprid 80 g L^?1 wettable powder (WP), imidacloprid 80 g L^?1 SC, thiamethoxam 100 g L^?1 water‐dispersible granule (WDG) and pyridaben 200 g L^?1 WP treatments resulted in 89–100% mortality against B‐biotype females only. CONCLUSION: In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, the essential oils described, particularly garlic, cinnamon bark and vetiver Haiti, merit further study as potential insecticides for the control of B. tabaci populations as fumigants with contact action. Copyright © 2011 Society of Chemical Industry     

Composition and biological activity of essential oils from Labiatae against Nezara viridula (Hemiptera: Pentatomidae) soybean pest

BACKGROUND: Plant essential oils have been recognised as an important natural source of insecticide. This study analysed the chemical constituents and bioactivity of essential oils that were isolated via hydrodistillation from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) against eggs, second instar and adults of Nezara viridula (L.). RESULTS: The major component of oregano was p‐cymene, and, for thyme, thymol. The ovicidal activity was tested by topical application; the essential oil from thyme was more effective. The fumigant activity was evaluated in an enclosed chamber; the LC₅₀ values for oregano were 26.8 and 285.6 µg mL^?1 for nymphs and adults respectively; for thyme they were 8.9 µg mL^?1 for nymphs and 219.2 µg mL^?1 for adults. To evaluate contact activity, a glass vial bioassay was used; the LC₅₀ values for oregano were 1.7 and 169.2 µg cm^?2 for nymphs and adults respectively; for thyme they were 3.5 and 48.8 µg cm^?2 respectively. The LT₅₀ analyses for contact and fumigant bioassays indicated that thyme was more toxic for nymphs and adults than oregano. Both oils produced repellency on nymphs and adults. CONCLUSION: These results showed that the essential oils from O. vulgare and T. vulgaris could be applicable to the management of N. viridula. Copyright © 2011 Society of Chemical Industry     

Exogenously applied hexaconazole ameliorates salinity stress by inducing an antioxidant defense system in Brassica napus L. plants

The ability of hexaconazole (HEX) to ameliorate salinity stress was studied in canola plants (Brassica napus L.). Canola seedlings were subjected to sodium chloride (NaCl) treatment. A treatment with 200 mM NaCl reduced growth parameters, chlorophyll content and protein content as well as increased the proline (Pro) content in canola plants. In addition, NaCl stress increased the endogenous, nonenzymatic antioxidants and the activity of antioxidant enzymes, such as peroxidase (POX; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1) and catalase (CAT; EC 1.11.1.6). When these plants were treated with a combination of NaCl and 50 mg L⁻¹ HEX, the inhibitory effects of NaCl stress were decreased by increasing the root growth, shoot growth, dry weight (DW), chlorophyll content, protein content and antioxidant enzyme activity by ameliorating the salinity injury. These results suggested that HEX has an important role in the enhancement of plant antioxidant systems and resistance to salinity in canola plants.     

The phytotoxicity of narrow distillation range petroleum spraying oils to valencia orange trees in South Australia. Part II: The influence of distillation temperature and spray timing on fruit quality

Petroleum oils sprays are used as pesticides on citrus in South Australia to control California red scale (Aonidiella aurantii Maskell), but may have phytotoxic effects on trees and fruit. As part of a programme to establish improved specifications for spray oils for South Australia, three oils with different 50 %-distillation temperatures were applied to trees each month from October to May for two seasons in order to observe their effects on fruit quality. The 50 %-distillation temperatures of the three oils were 211, 224 and 240°C at 10 mmHg (in order of increasing molecular weight) and the oils are subsequently referred to as the 211, 224 and 240 oils. The 224 and 240 oils significantly reduced the amounts of sugar and acid in the juice, and delayed and inhibited colouring. These effects increased in severity, the closer to harvest the trees were sprayed and the higher the distillation temperature of the oil. The 240 oil prevented full colour development, and caused ‘re-greening’ if sprayed later than February. Oil sprays applied to the same trees in the following season caused similar effects. However, if oil sprays were omitted in the following season, there was no residual effect, of the previous season's spray, on the sugar and acid contents or the colour of the fruit. Individual fruit weight was not affected in the first spraying season, but there was an increase in the average individual fruit weight in the second season, regardless of whether a second spray was applied that season or not. The effect was more severe, the closer to harvest the trees were sprayed and the greater the distillation temperature of the oil. The effects on yield resulted from a change in the number of fruit per tree.     

Growth,physiological status,and yield of salt-stressed wheat (Triticum aestivum L.) plants affected by biofertilizer and cycocel applications

This factorial study was conducted based on randomized complete block design with three replications in a greenhouse during spring 2015 to investigate changes in dry matter mobilization, grain filling period, and some physiological characteristics of wheat. Treatments were four salt levels [0 (S₁), 30 (S₂), 60 (S₃), and 90 (S₄) mM sodium chloride (NaCl) equivalent to 2.76, 5.53, and 8.3 dS m^?1, respectively], four biofertilizers levels [(no biofertilizer (F₀), seed inoculation by Azotobacter chroococcum Beijerinck strain 5 (F₁), Pseudomonas putida (Trevisan) Migula strain 186 (F₂), both inoculation Azotobacter?+?Pseudomonas (F₃)], and three cycocel levels [(without cycocel as control (C₀), application of 600 (C₁), and 1000 (C₂)?mg?L^?1)]. Salinity stress increased leaf electrical conductivity and decreased chlorophyll index, quantum yield, relative water content, and stomata conductance. However, the application of cycocel and biofertilizer reduced the negative impacts at each level of salinity tested. When treated with cycocel, salt stressed plants demonstrated a significant decrease in stomata conductance compared to the salt-treated plants with no cycocel. The results revealed that the maximum shoot and stem dry matter mobilization (0.89 and 0.67?g, respectively) and contribution of stem reserves to grain yield (38.01%) were observed in salinity severe stress (90?mM) and no cycocel application. The application of Azotobacter?+?Pseudomonas had the greatest grain filling rate (0.002?g day^?1) without salinity stress. The greatest grain filling period (43.26 days) was achieved by the highest cycocel level without salinity stress. The application of biofertilizer and cycocel as F₃C₂ had 24.7% more grain yield in comparison to the controls.