Ahmad Abdolzadeh

Beneficial effects of silicon nutrition in alleviating salinity stress in hydroponically grown canola, Brassica napus L., plants

Abstract Silicon (Si) is the second most abundant element in soil and effectively counteracts the effects of various abiotic stresses, such as drought, heavy metal toxicity and salinity, on plants. In the present study the ameliorating effects of Si nutrition supplied as 2 mmol L−1 sodium silicate were investigated on hydroponically grown canola (Brassica napus L.) plants under salinity stress (i.e. 150 mmol L−1 sodium chloride). Salinity decreased plant growth parameters such as tissue fresh and dry weights. These decreases were accompanied by increased lignin contents, Na+ ion accumulation, increased lipid peroxidation and decreased chlorophyll contents in plants. Silicon nutrition, however, enhanced plant growth parameters and led to the prevention of lignin and the Na+ accumulation in shoots, reduced levels of lipid peroxidation in the roots and higher levels of chlorophyll. As a result of salinity, catalase activity in the whole plant and both soluble and cell wall peroxidase activities in the shoots decreased. Silicon nutrition, however, increased the reactive oxygen species scavenging capacity of salt-stressed plants through increased catalase and cell wall peroxidase activities. Thus, silicon nutrition ameliorated the deleterious effects of salinity on the growth of canola plants through lower tissue Na+ contents, maintaining the membrane integrity of root cells as evidenced by reduced lipid peroxidation, increased reactive oxygen species scavenging capacity and reduced lignification.

Identification and quantification of phenolic and flavonoid components in straw and seed husk of some rice varieties (Oryza sativa L.) and their antioxidant properties

BACKGROUND Plant foods are rich sources of bioactive compounds that can act as antioxidants to prevent heart disease, reduce inflammation, reduce the incidence of cancers and diabetes. This study aimed to determine the phenolics and flavonoids profiling in three varieties of rice straw and five varieties of the seed husk of Iranian rice using high-performance liquid chromatography (HPLC). Furthermore, the antioxidant activities of the extracts were evaluated by using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and nitric oxide assays. RESULTS HPLC analyses showed that the gallic acid, pyrogallol, apigenin and rutin were the main phenolic and flavonoid compounds in all varieties of rice. In addition, the methanolic extracts of Hashemi and Ali Kazemi varieties showed the highest amounts of phenolic and flavonoid contents, respectively. Rice straw and husk of Iranian varieties showed considerable antioxidant activity and Hashemi indicated significantly (P < 0.01) higher DPPH and nitric oxide free radical scavenging activities when compared to the other varieties. CONCLUSION The present study revealed that rice straw and seed husk of Iranian varieties shows high antioxidant activities and they contain various types of phenolic and flavonoid compounds that could be use in food and medical industries.

Silicon Affects Transcellular and Apoplastic Uptake of Some Nutrients in Plants

The positive effects of silicon (Si) on growth of plants have been well documented; however, the impact of Si on plant nutrient uptake remains unclear. The growth, nutrient content and uptake of wheat (Triticum aestivum L.), canola (Brassica napus L.) and cotton (Gossypium hirsutum L.) plants were evaluated with or without application of 1.5 mmol L−1 Si. Application of Si increased dry weights by 8%, 30% and 30% and relative growth rate (RGR) by 10%, 13% and 17% in the cotton, canola and wheat plants, respectively. The plant relative water content (RWC) was also increased, but the plant transpiration was decreased by Si application. The uptake and content of Ca2+ were 19% and 21% lower in the cotton and wheat plants with Si than those without Si, respectively; however, Si application increased both K+ and Fe uptake and contents in all plant species. Silicon application reduced B uptake and content only in cotton and increased P and Zn2+ contents in all three plant species. The decrease in Ca2+ uptake by Si application was sustained even in the presence of metabolic inhibitors 2,4-dinitrophenol and sodium cyanide. Uptake of Ca2+ by Si application was enhanced or did not change when plant shoots were saturated with water vapor or their roots were exposed to low temperature. Thus, Si application increased the uptake of transcellularly transported elements like K+, P, Zn2+ and Fe. In contrast, Ca2+ uptake which occurred via both apoplastic and transcellular pathways was decreased by Si application, possibly through reduction of apoplastic uptake. More efficient nutrient uptake might be another promoting effect of Si on plant growth.

The potential of glauconitic sandstone as a potassium fertilizer for olive plants

This study evaluated the potential of glauconitic sandstone as a fertilizer for supplying potassium to plants. The glauconite sandstone (Maraveh, Iran), as analyzed by X-ray fluorescence, was composed of 2.24% potassium oxide plus high contents of silicon, aluminum and ferric oxide. One-year old olive trees, Olea europaea L., were grown in sand or hydroponic culture in a greenhouse under three potassium treatments. Modified Hoagland nutrient solutions based on potassium treatments including 0.5 mM K+, 5 mM K+ and 400 g glauconitic sandstone powders (per 10 L in hydroponics and per 2.5 L in sand instead of K+ supply) were used in both cultures. Plants grown under the three different potassium treatments did not show any potassium deficiency symptoms. In the sand culture, growth and potassium content were higher in plants fed with 5 mM potassium than with the other two potassium treatments. Growth retardation and decreased potassium content in plants fed with 0.5 mM potassium were more severe in the hydroponic culture than in the sand culture. However, plants fed with 400 g glauconitic sandstone showed higher growth in the hydroponic culture than the sand culture. Thus, glauconitic sandstone has the ability to release potassium and can be utilized in combination with other potassium fertilizers.

Redox changes accompanying storage protein mobilization in moist chilled and warm incubated walnut kernels prior to germination.

Alterations in the redox state of storage proteins and the associated proteolytic processes were investigated in moist-chilled and warm-incubated walnut (Juglans regia L.) kernels prior to germination. The kernel total protein labeling with a thiol-specific fluorochrome i.e. monobromobimane (mBBr) revealed more reduction of 29-32 kDa putative glutelins, while in the soluble proteins, both putative glutelins and 41, 55 and 58 kDa globulins contained reduced disulfide bonds during mobilization. Thus, the in vivo more reduced disulfide bonds of storage proteins corresponds to greater solubility. After the in vitro reduction of walnut kernel proteins pre-treated by N-ethyl maleimide (NEM) with dithioerythrethiol (DTT) and bacterial thioredoxin, the 58 kDa putative globulin and a 6 kDa putative albumin were identified as disulfide proteins. Thioredoxin stimulated the reduction of the H(2)O(2)-oxidized 6 kDa polypeptide, but not the 58 kDa polypeptide by DTT. The solubility of 6 kDa putative albumin, 58 and 19-24 kDa putative globulins and glutelins, respectively, were increased by DTT. The in vitro specific mobilization of the 58 kDa polypeptide that occurred at pH 5.0 by the kernel endogenous protease was sensitive to the serine-protease inhibitor phenylmethylsulfonyl fluoride (PMSF) and stimulated by DTT. The specific degradation of the 58 kDa polypeptide might be achieved through thioredoxin-mediated activation of a serine protease and/or reductive unfolding of its 58 kDa polypeptide substrate. As redox changes in storage proteins occurred equally in both moist chilled and warm incubated walnut kernels, the regulatory functions of thioredoxins in promoting seed germination may be due to other germination related processes.

Synthesis and antibacterial activity of stable bio-conjugated nanoparticles mediated by walnut (Juglans regia) green husk extract

Abstract Nanoparticles have gained significant attention in recent years due to their numerous applications in various aspects of human life. A variety of methods have been investigated for synthesis of nanoparticles among which, biogenic approaches are considered as both simple and eco-friendly. Here, a new single-step biological approach was employed for synthesis of silver chloride nanoparticles (AgCl-NPs) at room temperature, using walnut green husk extract. Macromolecules present in the plant extract, which might act as bio-reductants and/or stabilisers of nanoparticles were characterised by Fourier transform Infrared spectroscopy. X-ray diffraction pattern and transmission electron microscopy revealed that 1 mM of AgNO3 produced mostly spherical nanoparticles in a range of 4–30 nm in diameter with an average of 16 nm. Interestingly, the synthesised nanoparticles showed significant inhibitory effects against Escherichia coli and Staphylococcus aureus clinical isolates. Altogether, these data suggest a new encouraging application of a medicinal plant bound with synthesised AgCl nanoparticles.