نشریه فیزیولوژی محیطی گیاهی
پیاپی 49 (بهار 1397)

In order to investigate the activity of antioxidant enzymes of 14 tea clones under normal and drought stress conditions, two separate experiments were carried out in a randomized complete block design with two replications in 2017 at Fashalem Tea Research Station in Rasht. Irrigation in both designs was carried out routinely until July 22 followed by a drought stress treatment for one plot until August 22 when tea leaves were harvested. Tea leaves from each plot of the both experiments were then removed and transferred to a freezer at -80 °C. The activity of the antioxidant such as ascorbate peroxidase, superoxide dismutase, catalase, peroxidase, phenylalanine ammoniaase, lipid peroxidase, malondialdehyde, β-carotene, and lycopene were measured. The results showed that drought stress increased the activity of antioxidant enzymes. Based on the results obtained from the mean comparisons, clones 100, 399 and Bazri, had the highest activity for ascorbate peroxidase, superoxide dismutase, catalase, peroxidase, phenylalanine ammoniaase, and lipid peroxidase under drought stress conditions. On the other hand, these clones had the lowest contents of malondialdehyde. Clones 278 and 276 on the other hand, had the least values of antioxidant enzymes under drought stress conditions (except malondialdehyde) and were considered as sensitive clones.

Biochar has recently attracted lots of attention as a viable strategy for increasing crop productivity. Water shortage limits the productivity of agriculture, and one possible solution to this problem is the application of biochar. The objective of this study was to investigate the effects of biochar on physiology and yield of pumpkin (Cucurbita pepo L.) under different irrigation regimes. For this purpose, a factorial experiment in randomized complete block design with four replicates was conducted in Gorgan, in two successive years (2014-2015) and consisting of a factorial combination of four irrigation regimes including 45%, 60%, 75%, and 90% (I1-I4) of maximum allowable depletion (MAD) of available soil water (ASW) and biochar was applied at rates 0, 5, 10, and 20 tons per ha(B0–B20). Drought increased the activity of antioxidant enzymes, and the content of reactive oxygen species in leaf compared to control. In contrast, all of the antioxidant activities, reactive oxygen species and proline contents of leaves in soil treated with biochar, particularly at B20 biochar, declined. With the addition of biochar, the contents of MDA, O2•− and H2O2displayed remarkable decrease, however, maximum and minimum of these substances belonged to I4B0 and I1B20, respectively. Interestingly, biochar application alleviated the negative impact of reduced irrigation on the leaf gas exchange parameters, crop yields, water use efficiency, chlorophyll content, uptake of nutrients, and plant water status. Measured and simulated results revealed a special biochar application threshold for each irrigation regime with respect to seed yield. Response rate to biochar was ceased at lower biochar rates by prolonging irrigation. But the response of I2 treatment to biochar ceased at higher biochar rate as Bcritical (14 t ha-1). This implies that I2 improved response of pumpkin to biochar, which was accompanied by its higher WUE. These results indicate that biochar amendment could be considered as a successful strategy for improving the water productivity and increased crop production in study region (Gorgan).

In order to evaluate the effect of spraying humic acid on some morphological and physiological traits of fava bean, a factorial experiment was conducted in a randomized complete block design with three replications in Chalous during 2014-16. The investigated factors included spraying time at three levels (before planting, mid-vegetative growth, and the beginning of reproductive growth) and the amount of humic acid spraying at four levels (0, 200, 300, and 400 mg/l/ha). The results of analysis of variance showed that the interaction of year × amount of humic acid on the most studied traits showed a significant difference at a probability level of 1%. Also, interaction of year × consumption time of humic acid had a positive and significant effect on dry weight of 100 seeds, grain yield, and nitrogen and potassium contents of seeds at p≤0.01. Triple interaction of year × amount × consumption time of humic acid on nitrogen, phosphorus, and potassium contents were significant at p≤0.05. Comparison of means showed that spraying humic acid at 200 mg /L/ha had a positive and significant effect on fresh weight of 100 seeds and grain yield. Also, spraying humic acid at 300 mg/L/ha at the second stage of vegetative growth in the second year was effective on the concentrations of potassium and phosphorus in seeds.

To evaluate the effects of using various levels of superabsorbent and irrigation regimes on yields of Capparis spinosa plant an experiment was performed based on a randomized complete block design with three replications in the Research Field of Emamzadeh Jaafar Gachsaran in 2015. The main factor consisted of three irrigation regimes (once in a month, once every two months, and no irrigation) and a sub-factor at four levels of superabsorbent by Tarawat A200 applications (no superabsorbent, 75, 150, and 225 g/plant). Results revealed that the highest number of branches, collar diameter, height, and chlorophyll belonged to the plants irrigated every two months with 150 g superabsorbent and the highest value of carotenoids was observed in control plants. The highest plant survival rate was observed in 225 g/plant superabsorbent treatment alone. Irrigation levels had positive effects on the morphological characteristics of the plant so that the irrigation level of once every two months had more yield than the other levels. Findings suggest that the application of superabsorbent material in dry land condition could increase the yield by mitigating the effects of the drought stress.

Because of the importance of identifying the native genotypes and selecting the appropriate cultivars for successful development of olive tree cultivation, the present study was conducted to evaluate the selected oil and table genotypes compatible with climatic conditions of Gorgan. The experiment was done in a completely randomized design with three replications on 24 genotypes in Hashemabad complex in Golestan province. The maturity index of fruit was measured according to a method suggested by International Olive Oil Council and the percentage of oil was determined using a soxhlet method. Six genotypes with higher percentage of oil were selected and the physicochemical properties of the oil and the percentage of fatty acids were determined. Results showed that the highest and lowest fruit weights were observed in genotypes I7 and E6, respectively. The highest percentage of fruit flesh was observed in I7. E11 and D5 had the highest percentages of oil in dry and fresh matter. The lowest acidity was observed in B7 and the lowest peroxide was seen in E11. Genotypes F1 and E11 had the highest oil phenolic compounds. A10 showed the highest amounts of chlorophylls and carotenoids. F9 had the lowest indexes of K232 and K270 and following that A10 had the lowest index of K270. The highest percentage of oleic acid and the lowest percentage of linoleic acid were observed in A10. Genotype B7 had the lowest percentage of palmitic acid. Due to fruit weight, percentage of flesh and fruit sphericity, eight table genotypes were selected for further study. Among the selected table genotypes, genotype I7 had the highest levels of flavonoids, phenolic compounds, antioxidants, and anthocyanin. According to the results, the best oil genotypes were A10 and E11, the best table genotype was I7 and the best dual-purpose genotypes were F10 and B7.

To study the effects of different concentrations of chlormequat chloride and different levels of nitrogen on some physiological and biochemical characteristics and yield of barley (Hordeum vulgare L.) cultivar makuyi a factorial randomized complete block design was used with 4 replications in spring 2015. Treatments included chlormequat chloride concentrations (0, 500, 1,000, and 1500 mg/ha) and nitrogen at 3 levels (50, 100, and 150 kg/ha). Results suggest a significant difference between interaction effects of chlormequat chloride and nitrogen fertilizer on chlorophyll content, relative water content, yield and protein percentage, and activity of superoxide dismutase and catalase enzymes at 1% probability level and in the number of seeds per spike, 1000 seed weight, and glutathione peroxidase enzyme activity at 5% probability level. An increase in the consumption of nitrogen fertilizer decreased the relative water content of leaves due to reduced leaf water potential. Chlormequat chloride by transferring sufficient photosynthetic material to the seeds played an important role in their filling and increased seed weight. Also, the activities of superoxide dismutase, catalase, and glutathione peroxidase enzymes were decreased by increasing the consumption of chlormequat chloride concentration and nitrogen uptake. In general, through applying 1500 mg/ha chlormequat chloride and 150 kg/ha nitrogen, the highest chlorophyll content, relative water content, yield components, yield, and protein percent were obtained.

Allelopathy can affect the plant growth and change the soil nutrient contents. The aim of this study was evaluation of the allelopathic effects of Alhagi maurorum L. and Cardaria draba L. as two important weeds in wheat fields on nutrient absorption of this crop. Pot experiments were designed to study the allelopathic effects of A. maurorum and C. draba shoots on mineral nutrient contents in wheat. The absorption of high demand (NO3-, K, Ca2 and P) and low demand micronutrients (Fe2 and Cu2) in roots and shoots of wheat plants reduced in plants cultivated on rhizospheric soil of A. maurorum and C. draba. Allelopathy did not affect absorption of Mg2, Mn2, and Zn2. Allelopathic effect of A. maurorum was significantly (P

Cyanobacteria are gram-negative photosynthetic organisms and one of the most successful groups of organisms this planet has ever seen. They include some of the first life forms to evolve on Earth. During their long evolutionary history, cyanobacteria have undergone functional modifications, and these are responsible for their versatile physiology and wide ecological tolerance. The ability of cyanobacteria to tolerate high temperature, UV radiation, desiccation, and water and salt stresses contributes to their competitive success in a wide range of environments. Various species of cyanobacteria utilize different combinations of chromophores and phycobiliproteins to optimize their light-harvesting capabilities for photosynthesis. Phycobilisomes serve as the primary light-harvesting antennae for photosystem II in cyanobacteria and red algae. The aim of this research was to investigate phycobiliproteins in isolated heterocystous cyanobacteria from paddy fields in western Mazandaran. After collecting soil samples, cyanobacteria cultures were cultivated on a typical BG110. In addition to purification process, there were repeated sub-culturing on the solidified and liquid medium before the strains were characterized morphologically. Results indicated that because of adaptation of strains under accessible light condition, different species of cyanobacteria employ a high diversity of phycobiliprotein to optimize their light harvesting process in photosynthesis. Moreover, significant differences in the amounts of phycocyanin, allophycocyanin, and phycoerythrin were observed in various species. Maximum level of these protein compounds belonged to MGCY372 (Plectonema boryanum).