Iranian Journal of Plant Physiology
Volume:8 Issue: 1, Autumn 2017

Vanadium (V) is a transition metal consistently distributed in the Earth’s crust. At trace concentrations, it has been described as a beneficial element for some organisms; however, it is toxic at higher concentrations. This study was conducted hydroponically in a complete randomized design to investigate effects of V (0, 3.25, 7.5, and 15 mg L-1) on antioxidant system of sunflower. Results showed that all applied concentrations of V significantly decreased the plant growth, but increased the free amino acids, proline, malondialdehyde and H2O2 contents of plants. The antioxidant enzymes activities increased in response to the increase in V concentration. The activity of (Guaiacol) peroxidase showed a significant increase at 15 mg L-1 V while the activities of catalase, glutathione reductase, and ascorbate peroxidase decreased significantly by application of V. There was a slight increase in the superoxide dismutase activity at different concentrations of V. The study concludes that the applied concentrations of V induced oxidative stress in sunflower and (Guaiacol) peroxidase was a more effective antioxidant enzyme in scavenging the free radicals in this plant.

Salinity is an important environmental factor that limits plant growth and production. Grape is classified as salt sensitive plants. The object of this study was to evaluate effects of salinity on membrane lipid peroxidation, antioxidant components, and antioxidative enzymes activity in ten grape genotypes native to the regions around Urmia Salt Lake.Malondialdehyde content and protective enzymes activities in roots and leaves of ten genotypes increased significantly (p≤0.05) under salinity. Salinity had an obvious effect on the accumulation of total phenolics content and induced phenylalanine ammonia-lyase enzyme activity in all genotypes. H6 showed low increases in Malondialdehyde content, also this genotype showed good enzymes activities and total phenolics content and PAL activity. There were significant positive correlations (p≤0.01, r2=0.7) between antioxidative enzyme activities, total phenolics content, and phenylalanine ammonia-lyase activity in the leaves of all genotypes. It seems that H6 showed a higher capacity to tolerate salinity compared to the other genotypes.

Drought induced stress is one of the most significant environmental challenges. This study was designed to evaluate the effects of drought stress on crop yield and antioxidant systems during the vegetative period of wheat. The study was carried out in a greenhouse using factorial experiment based on complete randomized block design (RCBD) in three replications in Razi University in Iran from 2011 to 2012. In the pot experiment, water stress was applied at vegetative growth stage (soil moisture 50 ± 5% of field capacity from the stemming to flowering periods) and various bread wheat genotypes (‘Pishtaz’, ‘DN-11’, ‘Sivand’, and ‘Marvdasht’) were examined as the second factor. Results showed that drought stress at vegetative growth stage considerably decreased plant height and crop yield. Under drought stress, the lowest and highest reductions in crop yield were noted seen in ‘Marvdasht’ and ‘DN-11’, respectively. The occurrence of drought stress at the vegetative growth stage in the experiment significantly reduced soluble protein content and membrane stability index. While drought stress considerably increased superoxide dismutase (SOD), it had no effect on the catalase (CAT) and peroxidase (POD). The studied parameters suggested that drought resistance of ‘Pishtaz’ and ‘Marvdasht’ might be due to the enhanced activity of antioxidant enzymes and low lipid peroxidation. Finally, antioxidant enzyme responses were found to provide a beneficial tool for depicting drought tolerance in different wheat genotypes in arid and semiarid regions.

In order to investigate the effects of salt stress on biochemical and physiological responses of two cultivars of alfalfa (Medicago sativa L.) namely, Diabolourde and Yazdi, chlorophyll content, growth parameters, and proline contents of roots and shoots, reducing sugars contents of roots and shoots, and membrane injuries of the plant samples were subjected to 0, 100, 150, and 200 mM NaCl treatment in a factorial experiment based on a completely randomized block design. Findings showed that chlorophyll content, root dry weight, and shoot dry weight decreased in both cultivars under salt stress (p≤0.05). The reduction rate was more severe in Diabolourde cultivar than Yazdi. The root to shoot ratio had no significant differences in Diabolourde while increased significantly in Yazdi under 150 and 200 mM NaCl in comparison with control (p≤0.05). Reducing sugars content and proline content of roots and shoots increased significantly in both cultivars. The enhancing rates were more severe in Yazdi than Diabolourdeh. Also, the electrolyte leakage as a marker of membrane injuries increased in both cultivars as the enhancing rate was higher in Diabolourde cultivar in comparison with Yazdi. These findings showed that Yazdi cultivar employed resistance mechanisms more effectively than Diabolourde and therefore, it suffered lower injuries; higher growth parameters and lower membrane leakage in Yazdi cultivar are in agreement with this claim. According to the findings, Yazdi cultivar is proposed as a more tolerant variety for cultivation in saline area.

Considering the ever-increasing state of pollution in different aspects of the environment, ornamental plants and herbs such as Lavandula have become the center of attention mostly due to their availability and use in urban green spaces. Phytoremediation is a modern and economical method which can be applied to metropolises for decreasing metal contaminations in soil, water, and atmosphere. This study examined the contamination resistance of Lavandula against cadmium through 3 completely randomized block design experiments. The treatments included cadmium at 2 concentrations (0 and 100 mg) and DTPA at 2 concentrations (1 and 2 mM). Results suggested that heavy metal stress decreased morphologic properties under study and by adding DTPA the cadmium absorption decreased in Lavandula.

To study the effect of salicylic acid (SA) on the amount and quality of oil in different regions of sunflower inflorescence, a factorial experiment was conducted based on randomized complete block design with 3 replications at the University of Mohaghegh Ardabili, Ardabil, Iran. Salicylic acid at concentrations of 0, 0.1, and 0.2 g L-1 were sprayed on whole plant at 3 stages (twice before flowering and a third time after flowering) and kernels were collected from different regions of capitulum (inner, middle, and outer layers). Samples were taken fifteen days after flowering with 5-day intervals and the amount of oil and four fatty acids (palmitic, stearic, oleic, and linoleic acids) were measured. Results showed that SA increased content of oil and unsaturated fatty acids but decreased the amount of saturated fatty acids and improved the quality of the kernels obtained from the mother plant. Linoleic acid content increased more than oleic acid by spraying of SA and the concentration of 0.2 g L-1 SA was more effective. Kernel position had significant effect on the oil content and fatty acids, so that from the periphery toward the center there was a reduction trend in the oil and saturated fatty acid content.

Extraction methods are very important processes for separation of bioactive compounds of medicinal plants before analyses. Phenolic and flavonoid compounds include a broad variety of structures and functionalities that are required for the production of foods and food additives and there are different methods for the their extraction. In this study, total phenolic and flavonoid contents of leaf extracts from three varieties of Labisia pumila Benth (variety alata, pumila, and lanceolata) were investigated by microwave assisted extraction (MAE) and reflux extraction methods. Furthermore, DPPH radical-scavenging and ferric-reducing antioxidant power (FRAP) assays were applied to test the antioxidant activities. Results revealed that total phenolic (3.14, 3.03, 2.94 mg GAE g-1 DW) and flavonoid contents (2.08, 2.1, 1.85 mg Rutin g-1 DW) in the leaf extracts of Labisia pumila varieties alata, pumila, and lanceolata by MAE method were significantly higher than reflux extraction method, which was possibly responsible for the higher antioxidant activities in all three varieties of L. pumila Benth. These findings further illustrate that MAE has a bright prospect for extracting active ingredients from plant materials.

In order to study the effects of humic acid foliar spraying on morphological traits, photosynthetic pigmentation, and essential oil content of Dracocephalum moldavica, a factorial experiment was conducted based on a randomized complete block design with three replications in Saveh. The investigated factors included the use of humic acid at four levels 0 (control), 200, 400, and 800 mg/L and ethanol at four levels of 0 (control), 5, 10, and 15%. The measured traits were biological yield, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, essential oil percentage, and essential oil yield. Results showed that humic acid increased biological yield, chlorophyll a, chlorophyll b and total chlorophyll, essential oil percentage, essential oil yield, carotenoid, and free sugar. The highest positive effect was observed in 400 mg/L humic treatment. Ethanol increased biological yield, chlorophyll a, chlorophyll b and total chlorophyll, essential oil content, essential oil yield, carotenoid, and free sugar. In general, the highest positive effect was obtained in 10% ethanol treatment. Results showed that the use of humic acid with ethanol, especially in the combination of 400 mg/L humic acid with 10% ethanol, improved morphological characteristics, photosynthetic pigments, and yield of essential oil of Dracocephalum moldavica.