فصلنامه زیست شناسی گیاهی ایران
سال سوم شماره 1 (پیاپی 7، بهار 1390)

The present study investigates the allelopathic potential of Zhumeria majdae essential oil on acanola cultivar, Talaye. Essential oil was extracted by water distillation method, and was dissolved in 1% Arabic gum to achieve required concentrations. Catalase and Guiacol peroxidase activity in the presence of gum Arabic were the same as control; so gum Arabic did not affect enzyme activities. By increasing essential oil, the chlorophyll content decreased but the carotenoid content increased. Guiacol peroxidase activity in the presence of essential oil increased 20 and 60 percent but the increasing trend stopped in 60% of essential oil. Catalase activity increased significantly in the presence of 100% essential oil relative to control. Since relative oxygen species (ROS) increase in the presence of different concentrations of essential oil, plants increase guiacol peroxidase and catalase activity to decrease the ROS concentration, and thus, reduce their harmful effects on growth and development.

The aim of this study was identification of ecosystem units of Darkola's beech (Fagus orientalis Lipskey) forest and determination of effective environmental factors on their distribution. 52 vegetation plots were allocated at maximum vegetation cover during last spring by systematic-selective method. The plots were located 100-200 meter from each other based upon indicator stands concept. Five ecosystem units were distinguished based on floristic cover data by using TWINSPAN method. With respect to the units, we used one way ANOVA and discriminant analysis based on topographic and soil factors and plant biodiversity indices. Results showed that the ecosystem units which were classified on the basis of vegetation data could also reflect underlying differences in environmental features. Elevation, slope and north gravitation as topographical factors, percentage of clay as the only soil factor with Shannon- Wiener and Simpson diversity and Pielou evenness as biodiversity indices were the most important gradients respectively which constructed four discriminant functions. These functions, which were significant (P<0.01), showed that the five ecosystem units were correctly classified with 90.4 percentage goodness on the basis of environmental data and they were recognizable in five distinct groups in the biplot graph of discriminant analysis. Therefore, it was concluded that topographical characteristics and plant biodiversity indices had more influence on the formation of ecosystem units than physical and chemical properties of soil. We also concluded that and even an, ecological classification system were based upon vegetation analysis, it can present a suitable prediction of environmental characteristics.

Polluting the environment with heavy metals is on the increase and lead is one of the most important environmental pollutants. Salicylic acid is known as a plant antitoxic. In this research, the effects of different concentration of lead acetate and Salicylic acid were studied on some growth factors of eggplant (Solanum melongena L.), which is one of the main agricultural plant in continents of Asia and Africa. For this purpose, different concentrations of lead acetate including 0.005, 0.01 and 0.015 m, salicylic acid including 1, 5 and 10 µm were spread on the experimental plants, and control group were spread with water. Results showed that treatment with lead acetate caused changes in growth factors and treatment with salicylic acid caused growth plant improvement, significantly. Results were significant for some growth factors including fresh and dry weight, leaf area, CGR, RLGR and LAR, but were not significant for NAR and LWR (P≤0.05).

In oil producing countries, soil contamination by petroleum is one of the most important environmental pollutions. Crude oil can leak into the soil during extraction purification and transportation. The soil pollution could damage the environment as well as plant and animal populations. In this study, effects of different concentration of crude oil (0%, 2%, 4%, 6%, 8%, 10% w/w) on germination, growth and chlorophylls content in Rubinia pesudoacacia was investigated. The results showed that the germination rate and radicle lengths decreased significantly (p≤0.05) with increasing concentrations of petroleum. The growth parameters such as plant length, leaf number, leaf area, root and aerial part fresh and dry weight of plants decreased progressively from 1-4% crude oil in soil. In concentrations higher than 4% no growth was observed. The highest total leaf area of 503 cm2 was found in the control plant and least was found in the 4% soil (13 cm2) after 12 weeks. The cholorophyll b content progressively decreased from 1-4% crude oil in soil. The highest chlorophyll a content was measured for 2% plants. These results seemed to suggest that crude oil induced environmental stress in seedlings.

Effects of methyl jasmonate, low energy ultrasound, and dibutyl phthalate on the growth, certain physiological parameters, and taxol production in suspension-cultured hazelnut cell were investigated. The calli were obtained from seed cotyledons as explants on solid MS media supplemented with 2, 4-dichlorophenoxyacetic acid and benzyladenine at concentrations of 1 and 0.5 mg/L respectively. Methyl jasmonate with concentration of 100 µM, ultrasound waves with 40 kHz intensity, and dibutyl phthalate as an organic solvent with 10% concentration for in situ extraction were used. The time of all applications and the intensity of ultrasound and the concentration of methyl jasmonate were determined based on preliminary studies. According to the results, the cell growth and viability were decreased by treatments, compared to those of the control cells. All treatments increased hydrogen peroxide content, lipid peroxidation rate, and phenylalanine ammonia lyase activity, compared to the control. Taxol production was improved by all treatments and extracellular taxol was more affected than the intracellular one. In addition, in all treatments release of taxol and its specific yield was higher than those of the control cells. The most taxol production (3289.22 µg/L), taxol release percentage (98.39%) and specific yield of taxol (264.31 µg/g) were observed when dibutyl phthalate and ultrasound were applied together. Dibutyl phthalate significantly augmented the effect of other factors especially in respect to extracellular and total taxol production, taxol release and specific yield.

This study was carried out for evaluating morphogenesis responses of hypocotyl thin cell layers (TCL) of two alfalfas cultivars (Medicago sativa L. cv. Karysary and Rangelander) and also the effect of different 2,4-D concentrations on somatic embryogenesis was investigated. Sterilized seeds were cultured on SH medium without hormone. After a week, TCL (0.1 mm) obtained from hypocotyl segments were transferred to SH medium containing 2,4-D (1.5 mg/l). Produced calli were transferred to embryogenesis medium (SH medium containing four 2,4-Dconcentrations: 0, 5, 10, 15 mg/l) and one level of kin (1 mg/l). Then calli were transferred to regeneration medium (BOi2Y without hormone) and finally to the ½MS medium without hormone for plantlets growth. Callus induction was observed in all cultures of hypocotyl TCLs. After callus induction, the growth of the calli was performed suitability independent of the cultivar type. In regeneration medium, the somatic embryos appeared initially direct from TCL or indirect from callus as green dots that enlarged as the embryo develops through the globular, heart, torpedo and cotyledonary stages. The analysis of variance results showed that among different concentrations of 2,4-D there were significant differences in percentage of somatic embryogenesis (PSE) and number of somatic embryos per callus (NSC) (p<0.01). So that, maximum PSE and NSC occurred with 10 mg/l 2,4-D and minimum PSE and (NSC) without 2,4-D. PSE and NE (number embryogenesis) in Rangelander cultivar were significantly more than Karysary cultivar. Different concentrations of 2,4-D and cultivar × 2,4-D interaction had significant effect on plant regeneration (p<0.05). Plant regeneration was observed in SH medium of with and without 2,4-D. However, maximum plant regeneration was obtained in 5 and 10 mg/l of 2,4-D. Therefore, 2,4-D had the highest role on somatic embryogenesis from hypocotyl TCL.

The effect of ecogeographical factors on genetic similarity was investigated among five populations of Onobrychis viciifolia (sainfoin, Fabaceae) in East-Azarbaijan, Iran using RAPDs and bulked DNA. A number of 10 individual plants were randomly selected from each population. A number of 10 primers were tested, among which five producing the maximum numbers of clear and reproducible bands were selected. RAPD patterns were repeated three times for each primer to ascertain the reproducibility. The genetic distance between populations was measured based on Nei's Genetic distance, and the genetic similarity among the populations was assessed using UPGMA dendrogram based on Nei's distance matrix. The five primers produced a total of 12 polymorphic bands. The percentage of the bands produced by each primers ranged from 16.7% to 25%. The largest and shortest genetic distances were detected between Bonab and Heris (0.4904) and Amand and Khosroshahr (0.0572), respectively. On the UPGMA dendrogram, two populations of Sarab and Heris were nested within one cluster, and Amand and Khosroshahr in another cluster, while Bonab was completely separated from all other populations. The similarity between these pairs of populations could be attributed to the ecological similarity, because Bonab and Heris populations were distributed in regions with high altitude with cold climate, while Amand and Khosroshahr populations grew on salinity soils with warm climate. Separation of Bonab population from all others could be due to growing on the high saline soils and also being geographically very distant. Our results showed that RAPDs were capable to detect ecotypes of Sainfoin, and that they were affected by ecological factors.

Quality wise, most citrus species from North of Iran are appreciated by the Iranian peaple. They, therefore, deserve commercial and research value. To protect their cells and tissues from oxidative damage, most plants produce metabolites such as carbohydrates, amino acids, anti-freeze protein and antioxidants. Determination of lipid peroxidation, and detection of anti-freeze protein were used to explore the mechanism by which a plant could resist to cold stress. In this research, two species of citrus family, citrange (Citrus sinensis) and bitter orange (Citrus sinensis x Poncirus trifoliata) were subjected to a range of temperature. Results showed that a protein with molecular weight of 23 KD was produced in both citrus species at temperature below zero degree. On the other hand, lipid peroxidation in both species increased only slightly in response to cold stresses below 0°C.