Spermidine effect on biochemical properties consisted of activity of peroxidase, ascorbate peroxidase, relative water content, soluble sugar, and electrolyte leakages in cucumber (Cucumis sativus L.) was investigated. An experiment was conducted based on CRD with three replications in Islamic Azad University, Shiraz Branch. The first factor was included different irrigation courses at three levels; irrigation every other day, irrigation three days in between and irrigation five days in between. Second factor was included foliar application with three different concentration of spermidine (0, 1 and 2 mM). The resuls of variance analysis for interaction effect of different courses of irrigation and various concentration of spermidine on peroxidase enzyme activity, ascorbate peroxidase activity and relative water content was significant. The results also showed that plants that recived irrigation five days in between with 2mM Spermidine had the highest activity of peroxidase and ascorbate peroxidase enzyme. The interaction of different levels of irrigation and Spermidine foliar applciaiton on sugar solution and electrolyte leakages was not significant. In conclusion the effect of 2mM Spermine on peroxidase enzyme activity, ascorbate peroxidase activity and relative water content was significant.

With regard to decrease of precipitation and poor distribution of rainfall during the dry phenomenon of urban, green spaces face problems. In fact, one of the most important environmental stress is drought stress at different stages of plant growth such as seed germination, seedling establishment and crop production. The effect of drought stress, plants photochemical activity ceased Calvin cycle enzymes and chlorophyll content also varies in the process of photosynthesis under drought stress. Under drought stress, reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide radicals (O2 • -) and hydroxide (OH •) increase their accumulation in cells that can lead to oxidative stress. To neutralize ROS, antioxidant enzymes systems in plant such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) are active. The response of antioxidants depends on the lack of water, the intensity of the stress and the type of plant species. Also, it is well known that photosynthetic systems in higher plants are most sensitive to drought stress. Indeed, drought is one of the factors affecting photosynthesis and chlorophyll content. Some of researchers reported that chlorophyll might estimate influence of environmental stress on growth because these parameters were closely correlated with the rate of carbon exchange. The aim of this study was an investigation of effect of water deficit different levels on antioxidant system and lipid peroxidation in two species of marigold. Therefore, an experiment was carried out as factorial in a randomized complete block design with three replication at Shahid Chamran University of Ahvaz in 2014 year.
Experimental treatments were irrigation with three levels: 100% ETcrop (no stress), 75% ETcrop (moderate stress) and 50% ETcrop (severe stress) and two species of marigold (African and French). Catalase activity decreased absorption at a wavelength of 240 nm through catabolizing on the basis of H2O2 according to Beers and Sizer (1952). Peroxidase activity decreased absorption at a wavelength of 470 nm that was measured by using Hemeda and Kelin (1990). Ascorbate peroxidase enzyme extracted from leaf based on defects in the wavelength of 290 nm that was measured by Nakano and Asada (1987). The final product of membrane lipid peroxidation malondialdehyde concentration as the reaction thiobarbituric acid (TBA) was measured. Also, chlorophyll a, b and total chlorophyll were calculated by Arnon’s equations and chlorophyll content index (C.C.I) was measured by chlorophyll content meter (SPAD-502).
Results of analysis of variance showed that irrigation treatment had significant effect on chlorophyll a, total chlorophyll (Chl a), chlorophyll content index and catalase peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde while there was not significantly difference between two species of marigold on any of the measured biochemical characteristics. Also, results revealed that amount of leaf chlorophyll a and total chlorophyll (chl a) were reduced by increasing water deficit. In fact, amount of total chlorophyll, chlorophyll a, b and chlorophyll content index were higher in plants that were received 100% ETcrop than 75 and 50% ETcrop. ,The results of enzyme activity were similar to total chlorophyll and chlorophyll a and b. Amount of decreased chlorophyll a and total chlorophyll in plants were received 50% ETcrop were 24% and 47.46%, compared with 100% ETcrop, respectively.
Result showed that different levels of irrigation were significantly different at 5% level on catalase, peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde concentration. Catalase, peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde concentration were increased by reducing the amount of irrigation while there were no different between two species of marigold and interaction between species and irrigation was not effective on measured indexes.

Ascorbate as a strong antioxidant has a considerable bio effect on growth of plants, such as increase in their tolerance against environment stresses. In this investigation, the effect of salt stress and its interaction with ascorbate on amount of proline, catalase and ascorbate peroxidase enzymes and MDA in a medicinal plant of Cuminum cyminum L. was randomly studied in the green house conditions with three replications. Plants were treated by different concentrations of NaCl (0, 25, 50, 75, 100, 125 mmolar) and ascorbate (9 mmolar). In the plants treated with salt, the amount of proline, antioxidant enzymes activity and MDA were increased with increasing NaCl concentrations. The plants treated with NaCl and ascorbate at the same time in a same NaCl concentration, the amount of proline, catalase activity, ascorbate peroxidase and MDA were increased. The results indicated that the ascorbate was one of the antioxidants that caused an increase in resistance of Cuminum cyminum L. to salt stress.

To understand the Eco physiological adaptation mechanisms of Fagus orientalis Lipesk to altitude changes, the activities of Peroxidase (POD), Catalase (CAT), and Ascorbate peroxidase (APX) in leaves of Fagus orientalis in different altitudes (A1: 700 m, A2: 1200 m, A3: 1700 m above sea level) Was studied in the forests of Guilan. The sampling of leaves was collected from southern and northern parts of the crown of healthy and mature trees. The results of analysis variance showed that there was a significant difference between and within the population for the activity of catalase and peroxidase enzymes at the probability level of 0.05 and with increasing altitude, the activity of catalase and peroxidase were increased but the activity of Ascorbate peroxidase enzyme was initially increased and its level of activity decreased from the middle altitude with increasing altitude. Also, the results showed that the enzymatic activity of peroxidase and catalase in the northern leaves was more than the southern leaves that collected in crown of the trees.

Salinity is one of the most important factors that limit plant growth and production in the whole word. Compounds, which are able to reduce the damaging effects of various stresses such as salinity, should be of great important. In this investigation, the effects of spermidine on salt tolerance of Matricaria recutitaa were investigated. The results showed that, salt stress in chamomile plants caused the reduction of growth and increased the amounts of hydrogen peroxide, malondialdehyde and the activity of ascorbate peroxidase and guaiacol peroxidase. Pre-treatment of chamomile plants with spermimdine had no significant effect on shoot growth and the activity of ascorbate peroxidase enzyme, while reduced the content of hydrogen peroxide and malondialdehyde obviously, and increased the root growth and activity of guaiacol peroxidase significantly. Application of spermidine with methylene blue reduced the effect of spermidine on the increment of root growth, decrease of hydrogen peroxide, malondialdehyd and ascorbate peroxidase activity while had no significant effect on shoot growth and guaiacol peroxidase activity. Therefore, it seems that Spd effects on these physiological parameters are through nitric oxide and guanylate cyclase pathway however, more studies required for detail investigations.

Deficiency of nitrogen may lead to decrease in yield and yield potential of crop plants. An experiment was done under glasshouse conditions in order to investigate nitrogen levels and salicylic acid interaction on some physiologic traits of borage (Borago officinials L.). In this experiment various levels of nitrogen (including; 27.5, 55, 110, 220 and 330 mg/L from ammonium nitrate) and salicylic acid (including; zero, 400, 800 and 1200 µM) was used. The results indicated that stomatal conductance, photosynthesis rate, respiration rate, chlorophyll a, chlorophyll b, carotenoids, proline, and ascorbate peroxidase, were increased by increasing of nitrogen level. However, intercellular CO2 concentration, anthocyanin, flavonoids, soluble carbohydrates, catalase, and peroxidase were decreased. Among nitrogen levels, the maximum effect was obtained by 220 and 330 ppm treatments. Furthermore, salicylic acid spraying led to promote stomatal conductance, photosynthesis rate, transpiration rate, photosynthetic pigment content, proline, anthocyanin, flavonoids, soluble carbohydrates, and catalase, peroxidase and ascorbate peroxidase enzyme, but not intercellular CO2 concentration. The highest values of stomatal conductance, photosynthesis rate, transpiration rate, photosynthetic pigment content, proline, anthocyanin, flavonoids, soluble carbohydrates, and activities of catalase, peroxidase, and ascorbate peroxidase enzymes were achieved by 800 and 1200 µM concentrations of salicylic acid and 330 ppm of nitrogen. The results showed that appropriate concentrations of salicylic acid can recover nitrogen shortage and improve the measured traits.

Camelina (Camelina sativa) is a flowering plant from the Brassicaceae family. This cold-resistant plant has high nutritional value and is a multipurpose plant. Salinity stress is a growing problem in the agricultural lands of Iran and the world, which reduces the growth and development of plants. How this plant reacts to salinity stress and how to improve its resistance have been considered in this category. Various improvers have been recommended to increase resistance to stress. In this research, chitosan and iron, together with salt, have been applied to Camelina. Chitosan is one of the compounds that stimulates the plant's immune system to protect against stress factors, and the iron element plays an important role in the structure of cytochromes, photosynthesis and respiration by fixing N2. In order to implement this research, this experiment was carried out based on a randomized block design with three replications at Kharazmy Universityin 1402. In the present research, we investigated the salinity levels of 0, 8, 12 ds/m, equivalent to 0, 5.12, and 7.6 g/L of NaCl, and chitosan treatment with concentrations of 0, 0.2, and 0.4 g/L, and iron was also investigated with concentrations of 0, 3, and 6 g/l and the interaction of their different concentrations to improve growth. Following salt stress, different enzymatic antioxidants showed different reactions. The activity of the ascorbate peroxidase enzyme increased after the increase in salinity stress, and compared to the control, the activity of the peroxidase enzyme increased in the beginning compared to the control and did not record many changes, and the activity of the enzyme phenylalanine ammonia-lyase (PAL) increased with increased salinity stress compared to the control. In the combined study of the effect of chitosan elicitor and iron element on salinity stress, it was observed that chitosan elicitor improved the stress conditions by increasing the activity of peroxidase enzyme, photosnthase pigments, shoot fresh weight, and decreasing MDA and H2O2, the activity of ascorbate peroxidase enzyme and anthocyanin did not change much and this indicates that the effect of elicitor and iron element on salinity stress has improved.

To study the effect of different levels of melatonin on the biochemical properties and the amount of expression of genes related to the activity of antioxidant enzymes in bread wheat, a split plot experiment was conducted based on a randomized complete Triticum aestivum block design. Irrigation levels (normal (FC = 80%)), mild stress (FC = 60%), and severe stress (FC = 40%)) were allocated to the main plots and melatonin foliar spray (zero, 50, 100, 150, and 200 μM) were assigned to subplots. The results showed that the flavonoid content and ascorbate peroxidase enzyme activity increased with the intensification of dehydration stress. The level of 100 µM melatonin had the highest flavonoid content, ascorbate peroxidase enzyme activity. The mean comparison interaction treatments showed that the highest content of proline, phenol, superoxide dismutase and catalase was assigned to the 100 µM melatonin foliar spray under conditions of extreme stress of dehydration. Also, the lowest amount of malondialdehyde was observed for the 50 μM melatonin foliar treatment under normal irrigation conditions. The highest content of chlorophyll a, chlorophyll b, carotenoid and grain yield were recorded in the treatment of foliar spray of 100 μM melatonin and normal irrigation conditions. In this investigation, the maximum expression of superoxide dismutase, ascorbate peroxidase, polyphenol oxidase and catalase genes were determined in the foliar spray of 100 and 150 μM melatonin levels under conditions of extreme stress. . The foliar spray of melatonin, especially at the level of 100 μM, could moderate the effect dehydration stress on grain yield by improving biochemical and antioxidant properties.

Salicylic acid (SA), as a plant growth regulator, has an important role in alleviating the oxidative damages caused by drought stress in plant cells. In order to study the effect of different levels of SA on soluble protein content, the activity of enzymatic and non-enzymatic antioxidants including peroxidase, superoxide dismutase, ascorbate peroxidase enzymes, ascorbic acid and hydrogen peroxide and malondialdehyde levels and some physiological characteristics of two chickpea cultivars, [Kaka (MCC414) and Jam (MCC361)] under drought stress conditions, a factorial experiment was arranged based on completely randomized design with three levels of SA (0, 0.5 and 1 mM) and two moisture regimes, including drought stress (25% of field capacity) and control (100% field capacity) with three replications. Salicylic acid solutions at 0.5 and 1 mM concentrations were sprayed on leaves at intervals of 15, 25 and 35 days after sowing. Control plants were sprayed with distilled water. Results showed that at 25% field capacity, just peroxidase activity was enhanced in both cultivars. Drought stress reduced membrane stability index and PSΙΙ photochemical efficiency. Only in MCC414 cultivar, SA increased hydrogen peroxide and malondialdehyde contents under drought stress. SA significantly increased the activity of antioxidant enzymes including peroxidase and superoxide dismutase in MCC414 cultivar and ascorbate peroxidase enzyme activity in both MCC414 and MCC361. SA had not significant effect on the ascorbic acid content (P<0.05). Results suggested that SA at 0.5 and 1 mM concentrations could considerably improve membrane stability index and enhance PSΙΙ photochemical efficiency through reducing chlorophyll fluorescence under 25% field capacity.

Yaghooti grape is the earliest ripening grape in Iran and has advantages such as good taste and high heat and drought resistance; but it has highly cluster density. Physiological alterations of Yaghooti grape in three growth stages, as well as the amount of accumulation of some physiological substances, under the three hormones gibberellic acid, indole-3-acetic acid, and abscisic acid. Abscisic acid hormone had the most positive effect on total chlorophyll and carotenoid levels. The average amount of total chlorophyll was equal to (25.51), (18.76) and (26.16) mg/ml in the pre-flowering, flowering, and post-flowering stages, respectively. Under three hormones, the protein level is greatly reduced by 70%, Gibberellin treatment in the third stage of cluster development caused a 26% increase in carbohydrate level. The guaiacol peroxidase increased under indole acetic acid, but other hormonal treatments decreased the amount of this enzyme in Yaghooti grapes. The biggest reduction was related to gibberellin treatment with nearly 80% of the control sample in the first and second stage of cluster development and 55% in the third stage. The amount of ascorbate peroxidase enzyme was accompanied by an upward trend under influence of abscisic acid. Also, all three hormones almost caused a decrease in catalase enzyme activity in all three developmental stages. Indole acetic acid increased the activity of polyphenol oxidase enzyme during stages. Gibberellin, apart from slightly increasing the activity of ascorbate peroxidase enzyme during flowering, strongly reduced the activity of three other enzymes during all stages.