نشریه فیزیولوژی محیطی گیاهی
پیاپی 42 (تابستان 1395)

Identifying tree species candidate for phytoremediation is very important. However, its prerequisite is conducting comprehensive studies on tree species and evaluation of the plants’ potential. The current research surveyed resistance of two native species of Hyrcanian forest Acer cappadocicum and Fraxinus excelsior at seedling stage. In this regard, one-year old seedlings of both species were grown under different concentrations of lead including 0, 100, 200, 300,400, and 500 milligram lead per kilogram soil during a growth season. During a growth season photosynthetic indexes such as gas exchange, net photosynthesis rate, stomatal conductance, transpiration rate, and substomatal CO2 concentration as well as growth and biomass allocation were studied. The results showed that the presence of lead as a heavy metal led to decline of photosynthesis performance of both species but the inhibitory effects of Pb was less in seedlings of ash. Height and diameter growth as well as seedling biomass of both species were decreased by negative effects of lead but there was no considerable difference between two species. Our finding showed that under the experimental condition, there was no significant difference between resistances of two native species to lead contaminated soil but for making a better decision, further studies are necessary with stronger contamination and for a longer period.

The purpose of this study was assessing the impacts of different chilling periods on the release of dormancy in walnut lateral buds, carbohydrates metabolism, phenol compounds content, and activities of soluble and cell wall peroxidase and polyphenol oxidase. In this line, one-year-old shoots were collected randomly from ten-year-old trees of Ziyarat village (Gorgan) in defoliation which were then cut into 9 cm pieces each with a single lateral bud and were subjected to different chilling treatments (0, 700, 1400 hour) at 4±1 °C and then forcing condition (25 ± 2 ◦C, 12 h light:12 h dark photoperiod, 20 µmol m−2 s−1). Results showed that 700 and 1400 chilling hours significantly increased percentage and rate of walnut lateral bud dormancy release and decreased time of initiation bud break in comparison with control. Chilling caused starch and non-reducing sugar degradation and resulted in the increase of reducing sugars. This had a positive significant relationship with the percentage of bud dormancy release. Phenols content, soluble and cell wall peroxidase activities increased up to 700 hour chilling while polyphenol oxidase activity increased up to 1400 hour as compared with control. It seems that the buildup of reducing sugars provides the required energy for dormancy release, and the increase of phenols and soluble and cell wall peroxidase activities result in decrease of oxidative stress and development of cold tolerance in buds. Moreover, rising polyphenol oxidase activity caused removing phenolic inhibitors and/or synthesis of antioxidant phenols. These processes in parallel promoted dormancy release of Persian walnut lateral buds.

An experiment was conducted for phytochemical analysis of the compounds of Rheum ribes weedat the phonological stage of flowering in Weed Science Laboratory of Gonbad-e Qabus University in 2015. Plant samples of Rheum ribes were collected from heights of Karizak Village of Kashmar. After identifying the Rheum species, various organs of stem, leaf, and inflorescence were separated from each other, dried and finally powdered. Chemical compounds like the organic matter, ash, crud protein, ADF, NDF, starch, soluble carbohydrates, and total phenols contents of the organs under study and a combination of organs were measured using the standardized phytochemical methods. Results of the variance analysis showed that there were significant differences in the phytochemical traits among various organs of Rheum ribes. Findings suggest that the highest percentage of organic matter, ash, crud protein, NDF, and ADF were obtained in the inflorescence, both the stem and leaf, leaf and inflorescence, and stem and inflorescence, respectively. The study also recorded the highest levels of total phenols in both in floresvence and combination of the organs while the lowest phenols contents were observed in the stem. Results generally showed variations in the content of phytochemical compounds under study in Rheum ribes organs. Therefore, regarding high productivity of Rheum ribes biomass and the role of phenolic compounds as well as suitable content of some primary metabolites, optimization of suitable method to extract these compounds is necessary.

Cherry (Cerasus avium L.) is one of the valuable native and broadleaf species that are either scattered or exist as a small group in the northern forests of Iran. This research was carried out to investigate the effect of altitude from the sea level on some of the growth characteristics of cherry in different altitudinal layers. For this purpose, after seeing different forests in the series of 1 and 3 located in Nesaroud, Ramsar forests, 60 cherry trees of thicker than 20 cm in diameter were randomly identified due to the lack of suitable abundance in other altitudes of three altitudinal classes (200-400, 600-800, and 1200 -1400 m) above the sea level. In this study, some of qualitative and quantitative characteristics of the given stands were measured and analyzed. The obtained results showed that the qualitative characteristic of diameter growth were significantly different at P≤0.05. It was also indicated that the amount of leaf flavonoids and the density of anthocyanin of Cerasus avium that create red color increased with an increase in the height from the sea level and the light intensity particularly the increase in the direct radiation of ultraviolet ray. The maximum density of flavonoids and anthocyanins are in the altitudes higher than 1200-1400 meter above the sea level.

Drought is one of the factors that affect medicinal plants. On the other hand, the role of mycorrhiza fungi was effective in improving the performance of some medicinal plants exposed to draught stress. For this purpose, an experiment was conducted as split-plot in a randomized complete block design with 3 replications in the Boyerahmad region during 2015 - 2016. The experiment factors consisted of irrigation levels (main plot) as irrigation after S1 =30, S2 =60, S3 =90, S4 =120 and S5 =150 mm water evaporation from evaporation pan class A and mycorrhiza fungi (sub plot) consisted of non-inoculation (NG), inoculation with mycorrhiza fungi species of Glomus mosseae (GM) and Glomus intraradices (GI). Results showed that the effect of year on the studied traits of Borage was not significant. The effect of drought stress on leaf area index of Borage was significant and in the irrigation after 30 and 60 mm evaporation the highest LAI was obtained. The application of mycorrhiza fungi Glomus mosseae and Glomus intraradices increased the amount of phenols of Borageby %13 and% 9, respectively as compared with the plants not inoculated with mycorrhiza fungi. Increase in the drought from 30 mm to 150 mm decreased evaporation, height, number of tributaries and chlorophyll fluorescence, but the application of mycorrhiza could increase the studied characteristics of Borage under drought stress conditions and decrease the negative effects of stress.

Drought is one of the environmental stresses that have been recognized as the most important limiting factor for plant growth and production in most parts of the world. The aim of this study was to investigate the effects of drought on morpho-physiological indicators of Cucurbita maxima L. in two forms independently and with spraying Kinetin at two concentrations on growth parameters, photosynthetic pigments, and soluble sugars in leaves and roots. To achieve this aim, a pot experiment in a natural environment based on a factorial randomized complete block design was carried out in the form of 9 treatments with four replications. Three levels of drought stress in vegetative phase consisting of 2/3 and 1/3 of field capacity equivalent to mild and severe drought stress were applied with two concentrations of Kinetin including 2 and 4 mg per liter in the form of shoot spraying. The results showed that drought stress reduced the growth parameters, photosynthetic pigments, and starch and application of kinetin increased them significantly. On the other hand, drought stress increased soluble sugars while kinetin application decreased them. Overall results showed that the use of Kinetin in this study could significantly reduce the negative effects of drought on Cucurbita maxima L.

To study the effects of combined application of nitrogen and Azotobacter at different plant densities on some quantitative and biochemical characteristics of spring corn, a split plot experiment was carried out in the form of randomized complete block design with three replications in Shoshtar. The treatments of the study were the combination of nitrogen and Azotobacter fertilizer at three levels: the main plot was %100 nitrogen as urea fertilizer, %70 nitrogen as urea Azotobacter, and %40 nitrogen as urea Azotobacter as the main factor and the subplot was plant density at three levels: 6 plants per square meter, 8 plants per square meter, and 10 plants per square meter. Characteristics such as seed yield, yield component, protein, and starch percentage were evaluated. The effects of nitrogen fertilizer and Azotobacter were significant on all traits. The highest seed protein contents were recorded in the treatments of %100 nitrogen as urea fertilizer and %70 of nitrogen as urea and the rest as Azotobacter. The highest average grain yield (552.6 grams per square meter) was obtained from %100 nitrogen treatment and the lowest level (376.7 grams per square meter) was recorded in %70 nitrogen and %30 Azotobacter treatment. Therefore, the combination of biological and chemical nitrogen fertilizers can also improve the efficiency of production and absorption of the sufficient nitrogen fertilizer to reduce nitrogen consumption which contribute significantly to a healthy environment and is an important strategy toward sustainable agriculture.

Air pollution has different effects on living organisms. Since plants facing different environmental conditions cannot move, they are forced to cope with difficult conditions and withstand a series of physiological and morphological changes. This study was done to investigate the effects of air pollution on some physiological indices of P. kansuensis plant. These indicators included chlorophyll pigments, carotenoids, anthocyanins, and protein content. The results showed that chlorophyll a, chlorophyll b, carotenoids, and proteins in the contaminated area as compared with the clean area increased significantly. But anthocyanin content in the clean area did not change significantly compared to the contaminated area. Also, analysis of catalase and superoxide dismutase activities in the polluted regions showed a significant increase in comparison with the clean regions. Therefore, air pollution in Tehran can have adverse effects on photosynthetic efficiency of plants and air purification. functions of the plants which are one of the goals of the green spaces in major cities in addition to the beauty of urban space.