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Magnetic field (MF) can have different effects on plant metabolism depending on its application style, intensity, and environmental conditions. This study reports the effects of different intensities of static MF (4 or 7 mT) on seed germination and seedling growth of bean or wheat seeds in different media having 0, 2, 6, and 10 atmosphere (atm) osmotic pressure prepared with sucrose or salt. The germination percentages of the treated seeds were compared with untreated seeds germinated in different osmotic pressure during 7 days of incubation. The application of both MFs promoted the germination ratios of bean and wheat seeds, regardless of increasing osmotic pressure of sucrose or salt. Growth data measured on the 7th day showed that the treated plants grew faster than control. After 7 days of incubation, the mean length of treated seedlings was statistically higher than control plants in all the media. The greatest germination and growth rates in both plants were from the test groups exposed to 7 mT MF. Strikingly, effects of static MF on germination and growth increased positively with increasing osmotic pressure or salt stress compared to their respective controls. On the other hand, MF application caused an increase in dry biomass accumulation of root and shoots of both seedlings; however, this effect was found statistically important in all the conditions for wheat but not for bean, in general.

In the present study, it was aimed to investigate the influence of exogenous mammalian sex hormones (MSH) (progesterone, b-estradiol and androsterone) on the morphological (root and shoot growth) and biochemical parameters (protein and sugar content, antioxidant enzyme activities, and lipid peroxidation and H 2 O 2 levels) of chickpea (Cicer arietinum L.) plants growing under control conditions. The solutions of hormones prepared at different concentrations (10 -4 , 10 -6 , 10 -9 , 10 -12 and 10 -15 M) were sprayed once on the leaves of 7-day plants. The plants were harvested on 18 days after the hormone treatment. Although all of the hormones at the tested concentrations significantly increased plant growth, soluble protein and sugar contents, and antioxidant enzyme activities [superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT)], they decreased H 2 O 2 content and lipid peroxidation level when compared with control plants. The activities of SOD, POX and CAT reached to the highest levels at 10 -6 M for progesterone, and 10 -9 M for b-estradiol and androsterone, which maximum growth, protein and sugar contents were determined. The same concentrations also resulted in the lowest levels for H 2 O 2 content and lipid peroxidation. It can be interpreted that the MSH improve plant growth and development by affecting some biochemical parameters including antioxidative system.

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Melatonin, known as an animal hormone and an antioxidant with a low molecular weight, is one of the most commonly used substances to improve plant resistance against various environmental stresses. However, there are no studies explaining the effects of melatonin on the relationship between defense system and mineral composition of plants under stressed and unstressed-conditions. The present study was conducted to investigate whether the mitigating effect of melatonin is associated with its modulating influence on the mineral elements of cold-stressed maize seedlings. The seedlings were treated with melatonin (1 mM) and cold stress (10/7°C) for 3 d separately and in combination. After 3 d, the seedlings were harvested to determine several physiological, biochemical, and molecular parameters. Melatonin application effectively mitigated the damages from cold stress, as demonstrated by higher relative water concentration, chlorophyll concentration and antioxidant enzyme activities (superoxide dismutase, guaiacol peroxidase, catalase, ascorbate peroxidase, and glutathione reductase), as well as lower superoxide, hydrogen peroxide, and malondialdehyde concentrations. Similarly, melatonin significantly ameliorated cold-induced reductions in the concentrations of potassium, phosphorus, sulfur, magnesium, iron, copper, manganese, and zinc. Besides, it further increased calcium and boron concentrations compared to cold stress alone. Our results reveal that melatonin has an important modulating influence on the mineral element composition of plants and mitigates cold stress through up-regulation of these elements and simultaneously enhanced antioxidant activity.

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MSHs could be used effectively to protect wheat seedlings from the destructive effects of salt stress by stimulating both enzymatic and non-enzymatic antioxidant mechanism and by promoting levels of osmotic protectants such as proline and sugars resulting in osmotic adjustment, carbon storage and radical scavenging in plants.