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Boron (B) toxicity often limits crop yield and the quality of production in agricultural areas. Here, we investigated the effects of calcium (Ca), silicon (Si) and salicylic acid (SA) on development of B toxicity, B allocation in canola (Brassica napus cultivar Sarw 4) and its role in non-enzymatic antioxidants in relation to yield of this cultivar under B toxicity. Canola seedlings were subjected to four B levels induced by boric acid in the absence or presence of Ca, Si and SA. The results showed that Ca, Si and SA addition ameliorated the inhibition in canola growth, water content (WC), and improved siliqua number, siliqua weight and seed index. The B content in shoots and roots and total B accumulation in the whole plant were increased in control plants under B-toxicity-stress, and these parameters were significantly decreased by addition of Ca, Si and SA. The shoot ascorbate pool (ascorbate, AsA, and dehydroascorbate, DHA), α-tocopherol and phenolics (free and bound) were increased under B toxicity, and were significantly decreased in most cases by addition of Ca, Si and SA, except α-tocopherol, which increased at low B levels (0, 25 and 50 mg kg soil). The glutathione content did not obviously change by B stress, while added Ca, Si and SA inhibited its accumulation under B stress. In addition, B toxicity reduced the shoot flavonoids content; however, this reduction was not alleviated by the use of Ca, Si and SA treatments. It could be concluded that growth and yield of canola plants grown under high B concentration improved after external application of Ca, Si or SA.

Nano-fertilizers are a new tool that can be used to address plant production challenges, and it addresses such nutrient deficiencies through smart agriculture approaches. Iron (Fe) is a vital element for several metabolic and physiological processes; however, Fe deficiency is common in poorly fertile soils (sand soil) and in arid areas. Therefore, additional research is required to select the most efficient form of iron absorbance. This research was implemented on broad bean plants (Vicia Faba L. var. major Harz) to examine the impact of three iron sources: nano-iron (FeNPs, T1), iron sulfate (T2), and chelated iron (T3) as a foliar spray on the morphological properties, physiological attributes, and nutritional status of these plants compared to the untreated plants (control). The obtained results showed that foliar spraying with FeNPs, chelated iron and sulphate iron fertilizers increased plant height by 35.01%, 26.2, and 20.4%; leaf area by 38.8%, 18.3%, and 8.1%; the fresh weight of the plant by 47%, 32.8%, and 7.3%; the dry weight of the plant by 52.9%, 37.3%, and 11.2%; and the number of branches by 47%, 31.3%, and 25.6 %, respectively, compared to the control treatment (CT). Furthermore, the application of FeNPs, chelated iron, and sulphate iron fertilizers improved the number of pods by 47.9%, 24.8%, and 6.1%; the number of seeds by 32.8%, 7.9%, and 2.8%; and seed weight by 20.8%, 9.1%, and 5.4%, compared to control treatment (CT). Additionally, foliar application of FeNPs showed the highest values of photosynthesis rate (Pn), water-use efficiency (WUE), total chlorophyll, and phytohormones (IAA, GA3) compared to all the other treatments. The anatomical structure revealed an enhancement of leaf size and thickness (epidermis cells and mesophyll tissue) affected by FeNPs treatment compared to other treatments. Foliar application of FeNPs also improved the total content of carbohydrates, crude protein, element content (N, P, K, Ca, Na, Fe, Zn, Mn, and Cu), and some amino acids such as lysine, arginine, phenylalanine, isoleucine, and tyrosine in the seeds of broad beans. Based on the above results, the maximum values of all tested measurements were observed when FeNPs were used as the foliar spraying followed by chelated and sulphate iron fertilizers. Therefore, these findings suggest that using FeNPs, as a foliar treatment, could be a promising strategy for reducing the Fe deficiency in sandy soil and enhancing plant growth, pod yield, and pod quality of broad bean plants in addition to being environmentally favored in arid areas.

A MELIORATION with silicon (1mM sodium silicate Na 2 SiO 3 ) or humic acid (50mg L -1 HA) was tested in counteracting the phytotoxicity of copper oxide nanoparticles (CuONPs) at 50, 100 and 150mg L -1 on Safflower plants (Carthamus tinctorius). Si sustained seed growth at (150mg L -1 CuO NPs). The application of HA increased copper concentration in seedling by about 5 to 10 fold, relative to the control at 50 and 100mg L -1 . Fresh weight of safflower seedlings were reduced significantly at 100mg L -1 CuO NPs. Si enhanced fresh and dry matter gain under 100 and 150mg L -1 CuO NPs, also HA improved dry matter at 100mg L -1 CuO NPs. Chlorophyll a and carotenoid contents reduced by about 60% and 50% at CuO NPs (100mg L -1 ), respectively as compared to control. Chlorophyll a and carotenoid contents reduced by about 60% and 50% at CuO NPs (100mg L -1 ), respectively as compared to control. Si or HA sustained Chl.a content unchanged and improved carotenoids contents at 100mg L -1 CuO NPs.Phenolics contents significantly increased under CuO NPs phytotoxicity. External application of HA provoked more phenolics content. Nano-CuO phytotoxicity reduced H 2 O 2 scavenging and lipid peroxidation inhibition %. Si or HA enhanced significantly lipid peroxidation inhibition % and H 2 O 2 radial scavenging %. Si or HA reflected significant enhancement of SOD and CAT enzymes under elevating concentrations of CuO NPs. Si enhanced significantly POD activity at (50, 100 and 150mg L -1 ) CuO NPs levels.

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Concerns about the vulnerability of agricultural production to climate change are increasing. The establishment of seedlings at early growth stages of crop plants, one of the most important determinants of high yield, is severely affected by extreme temperatures. Therefore, efforts must be made to achieve high germination rate and vigorous early growth under extreme temperature conditions.Alfalfa is a perennial forage crop with high yield, good quality and high protein content, but is frequently exposed to extreme temperature conditions. The primary purpose of this investigation was to test the hypothesis that L-ascorbic acid (AsA) and pyridoxine (B6) pretreatment can completely or partially alleviate the effect of extreme temperature stress on seed germination and other physiological activities of alfalfa seedlings. Such treatment could be of importance for the establishment of alfalfa seedlings under temperature conditions colder or hotter than the optimum.Several parameters were studied in alfalfa seedlings primed before germination with 50 ppm ascorbic acid or 50 ppm pyridoxine for 6 h and then subjected to various temperatures (10, 15, 20, 25, 30, 35 and 40°C) for 7 days.The germination percentage of alfalfa seeds was negatively affected by extreme temperature. The vitamin treatments failed to alleviate the depressive effect of extreme temperature stress on seed germination. Extreme temperature also induced a reduction in the growth, total water content and respiration rate of alfalfa seedlings. Seed soaking in vitamins modified the stress-induced changes in respiration rate and growth criteria. Temperatures above or below the optimum stimulated the accumulation of soluble carbohydrates in alfalfa seedlings. Treatment with AsA or B6 partially or completely retarded the stimulatory effects of extreme temperature on soluble carbohydrate accumulation in the seedlings except in the case of 40 °C, where a significant stimulation was detected. However, extreme temperature stress and its interactive effects with AsA or B6 induced an inhibitory effect on the accumulation of free amino acids and soluble proteins in the test seedlings.

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