Hamid Mohammadi

Comparison of fructan dynamics in two wheat cultivars with different capacities of accumulation and remobilization under drought stress

Remobilization of stored carbohydrates in the stem of wheat plants is an important contributor to grain filling under drought stress (DS) conditions. A massive screening on Iranian wheat cultivars was performed based on stem dry weight changes under well-watered and DS conditions. Two cultivars, Shole and Crossed Falat Hamun (CFH), with different fructan accumulation and remobilization behavior were selected for further studies. Water-soluble carbohydrates (WSCs) and fructan metabolizing enzymes were studied both in the stem penultimate and in sucrose (Suc) treated, excised leaves. Under drought, CFH produced higher grain yields than Shole (412 vs 220 g m(-2)). Also, grain yield loss under drought was more limited in CFH than in Shole (17 vs 54%). Under drought, CFH accumulated more graminan-type fructo-oligosaccharides than Shole. After anthesis, fructan 6-exohydrolase (6-FEH; EC 3.2.1.154) activities increased more prominently than fructan 1-exohydrolase (EC 3.2.1.153) activities during carbon remobilization. Interestingly, CFH showed higher 6-FEH activities in the penultimate than Shole. The field experiment results suggest that the combined higher remobilization efficiency and high 6-FEH activities in stems of wheat could contribute to grain yield under terminal drought. Similar to the penultimate, fructan metabolism differed strongly in Suc-treated detached leaves of selected cultivars. This suggests that variation in the stem fructan among wheat cultivars grown in the field could be traced by leaf blade induction experiments.

Nanocomposite films based on CMC, okra mucilage and ZnO nanoparticles: Physico mechanical and antibacterial properties

This work examined the physico mechanical parameters and antibacterial activity of CMC/okra mucilage (OM) blend films containing ZnO nanoparticles (NPs). Different proportions of CMC and okra mucilage (100/0; 70/30; 60/40 and 50/50 respectively), were mixed and casted to posterior analysis of formed films. The more colored films were obtained by higher contents of okra mucilage and adding ZnO nanoparticles. The incorporation of ZnO NPs into CMC film decreased the elongation at the break (EB) value of the films and increased the tensile strength (TS) value of the film. With increase in CMC concentration in the films, higher water vapor permeability and higher solubility in water were achieved. Microstructure analysis using SEM showed a smooth and compact surface morphology, homogeneous structure, and a rough surface for CMC, CMC+ZnO, and CMC/OM30%+ZnO, respectively. Nanocomposite films presented antibacterial activity against tested bacteria. Films contained okra mucilage showed more antibacterial activity. The inhibitory activities of resultant films were stronger against S. aureus than E. coli.

Effects of freeze and cold stress on certain physiological and biochemical traits in sensitive and tolerant barley (Hordeum vulgare) genotypes

ABSTRACT An experiment was performed as a split-plot design based on a randomized complete block (RCB) with three replicates. The aim was to explore physiological traits, catalase (CAT) and peroxidase (POD) activity associated with cold and freeze stress in four barley genotypes (two stress-tolerant genotypes and two sensitive genotypes). The genotypes were regarded as sub-plots and five temperature levels (namely 20, 4, 0, −4, −8°C) as main plots. The results revealed that the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content increased through freeze and cold stress from 20 to 4°C. This increase was more in the sensitive genotypes than in the tolerant ones. Subsequent to the increase in lipid peroxidation, the membrane stability index (MSI) decreased, thereby increasing the electrolyte leakage. The sensitive genotypes demonstrated greater reduction in the studied parameters. Upon the increase in the H2O2 content, the antioxidant enzymes CAT and POD also increased in order to collect and prevent H2O2 from damaging the cell and the plant. Compared with the sensitive ones, the tolerant genotypes indicated more increase in the enzymes. The H2O2 and MDA content decreased from −4 to −8°C, which could be due to intracellular freezing in the sensitive genotypes, but due to the detoxifying of the antioxidant enzymes in the tolerant genotypes. Compared with the POD content, the increase in the CAT content through cold stress was more, which could mean that it was possibly CAT which acted as the main inhibitor of H2O2 in cold stress in the barley plant.

Mitigating effect of nano-zerovalent iron, iron sulfate and EDTA against oxidative stress induced by chromium in Helianthus annuus L.

Due to its wide industrial application, chromium (Cr) is known to be a critical environmental pollutant. Contamination of water and agricultural soil by Cr inhibits crop productivity and their physiological and biochemical processes. The objective of the current work was to investigate the effects of appropriate reducing agents such as EDTA, iron sulfate (Fe2+), and zerovalent nano iron (Fe0 nanoparticles) on growth and physiology of sunflower plants under Cr(VI) stress. Results showed that the Cr uptake increased by increasing the amount of EDTA, leading to a significant reduction in morphological and physiological parameters except for MDA and H2O2 contents. Treatment with Fe0 nanoparticles and Fe2+ reduced Cr concentration in root and shoot, increased root and shoot dry weight, plastid pigments (chlorophyll and carotenoids) and proline contents; however, the level of MDA and H2O2 decreased significantly. All parameters were affected by Fe2+ during the first week of sampling; however, Fe0 nanoparticles affected all traits until the end of the third sampling stage. A statistically significant and positive correlation was found between root Cr concentration and MDA and H2O2 seedlings treated with EDTA, Fe2+, and Fe0 grown under Cr stress. From the result of this study, it can be concluded that sunflower has the potential for accumulation of Cr as a heavy metal, and treatment with Fe0 nanoparticles to prevent Cr uptake is more effective than other employed treatments.

Genetic Evaluation of Crown Freezing Tolerance and Some Physiological Traits in Barley (Hordeum vulgare L.) Lines

Genetic Evaluation of Crown Freezing Tolerance and Some Physiological Traits in Barley (Hordeum vulgare L.) Lines In order to investigate cold tolerance in 20 barley genotypes based on crown survival percentage, a greenhouse experiment was conducted as split plots with three replicates, with temperatures (-8, -10, -12, -14 and -16°C) as main plots and barley genotypes constituting subplots. Randomized complete block design was performed to analyze physiological traits measured after acclimation and before applying chilling temperatures. Crown survival percentage was measured zero at -16°C. Error was not significant for main factor in split plots, therefore, data analysis for -8, -10, -12 and -14°C was executed as factorial. Results indicated that temperature, genotype and their interactions had significant influence on the crown survival percentage. Also, the genotypes were significantly different in terms of LT50, the glycine betaine content and leaf relative water content before and after adaptation to cold. Comparison of the means, based on LT50 and crown survival percentage, suggested the genotype number 15 (with K-096M3 pedigree) as the most tolerant to crown freezing, and genotypes 36 (Schulyer), 15 (K-096M3) and 14 (GK Omega) as possessing the most desirable physiological traits, with genotypes 15 and 36 possessed the lowest difference before and after leaf relative water content, and the maximum quantity of glycine betaine after adaptation to cold. Cluster analysis of the genotypes, based on the aforementioned traits, divided them into three distinct tolerant, semi- tolerant and sensitive groups.....