فصلنامه زیست شناسی گیاهی ایران
سال پنجم شماره 2 (پیاپی 16، تابستان 1392)

Soil pollution by toxic metals is a serious problem for the environment and is also one of the environmental stresses for higher plants. Zinc as a heavy metal plays an important role in many biochemical functions of plants. However، excess amount of zinc is one of the most important growth limiting factors in acid soils. In this investigation five day seedlings of Zea mays L. for 12 days، under hydroponic conditions were treated with concentrations of 0، 400 and 600 of zinc sulfate also malic acid and citric acid 0. 32 mM together with zinc concentrations. Then، plants were harvested and dry weight، root and shoot length، Malondialdehyde (MDA)، H2O2 content and antioxidant enzyme activity (CAT، APX، GR and GPX) was measured. The results showed that by increasing Zn concentration from 400 to 600 µM، root and shoot dry weight and length were decreased، while MDA، H2O2 content، antioxidant enzyme activity were increased. Also، the present of citric and malic acids decreased toxicity effects. Generally، it was concluded that zinc at high concentration induced toxicity effects in Zea mays L. but presece of malic and citric acid decreased toxicity effects in this plant.

In this study، okra plants were exposed to different ultraviolet (UV) radiation for 12 days. After treatment، leaf surface، root and stem length، fresh and dry weight and photosynthetic pigments، protein and sugar content were evaluated and the results showed that their contents were significantly decreased under UV radiation specially in UV-B and UV-C. The anatomical studies indicated that thickness in the different organs was decreased. Also، it was observed that stomatal density، index contents and stomatal length were increased under UV radiation in UV-B and UV-C. Because of the effects of UV radiation on epidermal cells of stem، leaf and petiole were observed to have decreased epidermal length but epidermal breadth was increased specially in UV-B and UV-C. The results of this study showed that UV-B and UV-C had serious effects on okra plant، but UV-A wasn’t harmful to okra plants.

Mycorrhizas providea symbiotic associations in which the fungus obtains carbon from the plant، while providing the plant with a supply of phosphorus. On the other hand، periwinkle plants (Catharanthus roseus L.) have been investigated due to production of two medicinal alkaloids namely vinblastine and vincristine. In this evaluation، tryptophan was used as precursor of these alkaloids under tissue culture conditions. Inoculation by mycorrhiza induced the growth and survival of several species during acclimatization، which was the most important challenge of tissue culture. For this reason، the regeneration plantlets obtained under different concentrations of tryptophan، were exposed to acclimatization to mycorrhizal colonization and their shoot growth and biochemical factors were evaluated. Results from measurement of length، fresh and dry weights، soluble sugars and total protein content and also، chlorophyll a and b of shoots، indicated the positive role of these two treatments on growth of periwinkle plantlets under acclimatization. The highest amount of height and fresh and dry weight in shoots were obtained in colonized samples with Glomus versiforme and under 0، 150 and 250 mg/l tryptophan treatments، respectively. Also، the highest content of total protein and soluble sugars content was observed in G. versiforme colonized plants under 350 mg/l tryptophan treatment. Finally، evaluation of the chlorophyll a and b contents showed that the highest amount of these factors obtained in the colonized samples with G. versiforme and G. etunicatum، respectively، under 250 mg/l tryptophan treatment.

Plants use of water، air and soil plays an important role in changing ecological conditions. Therefore، the plants could be used to purity ecosystems from various pollutions such as heavy metal. In this study، heavy metals concentration such as، Ni، Mn، Zn، Fe and Pb in the plants and soils surrounding steel production industries in east west of Ahwaz city in the Mahshahr-Bandar Imam road was investigated. The results indicated that average bioavailable metal concentration in soil samples changes as Fe> Mn> Zn> Ni> Pb (mg. kg-1). The maximum value of Fe was measured in the shoot of Taraxacum kotschyi (891 mg. kg-1 DW) as a herb and Conocarpus erectus (860. 63 mg. kg-1 DW) as a tree، Zn and Mn maximum was assayed in the shoot of T. kotschyi with 108. 63 and 93. 90 mg. kg-1 DW، respectively. Also، the maximum concentration of Ni was measured in tree type of Eucalyptus camaldulensis with 10. 86 mg. kg-1 DW value. The Pb concentration was not determinable in plant and soil samples. The results of bioconcentration factor and translocation factor indicated that these factors were higher than 1 in most of the cases. Based on the study، it seemed that mentioned metal concentration in plants was lower than defined as threshold in a hyperaccumulator plant. However، it could be assumed that selected plants would be able to accumulate metal in shoot.

In this study، the effects of 0. 5 mg/l exogenous SA on some physiological and biochemical processes of Artemisia aucheri Boiss. under tree levels of salt stress (0، 50 and 150 mm/l) were investigated. The salt stress decreased the parameters of plant growth such as dry weight، aerial parts and roots length، total chlorophyll، carotenoids and potassium content. But، treatment of plant with SA under salt stress increased the above–mentioned parameters. At the same time، peroxidation of membrane lipids، percentage of membrane leakage، the amount of hydrogen peroxide and sodium content of the plant were increased under salt stress. On the contrary، the presence of exogenous SA decreased the above parameters. The obtained results indicated the modulator effects of salicylic acid on physiological processes of the Artemisia aucheri Boiss. under salt stress.

Wild pistachio is one of the tree species in semi-arid areas in Iran that has important environmental and economical- social impacts. This species has not been studied well anatomically and in some cases، distinguishing it from other varieties of Butmela is difficult. The aim of this research was to investigate the diversity of this species based on some anatomical leaf traits such as vascular tissue. For this reason leaves were collected from tree populations and they were kept in ethanol (70 %) for one month، then cross sections were prepared from each sample. Based on the results، the leaves of Pistacia atlantica were bifacial and they had short trichomes (glandular and covering) in both adaxial and abaxial surfaces. Thickness of central vascular tissue، thickness of leaf and length of central vascular tissue had the most important roles in grouping، respectively. Also، no differences were found between male and female trees for anatomical traits. The results from this study could be used in the taxonomy of this species. For example، the form of central vascular tissue in this species was generally oval.

In this study، the hypothesis that defense response in leaves of the oilseed rape is induced under isothiocyanate stress was investigated. The effects of different concentrations of of methyl and propyl isothiocyanates (0، 1، 10 and 100 mM) were evaluated on accumulation of hydrogen peroxide، phenolic compound content and PAL and GST enzymes activities in Brassica napus L. Oxidative stress in isothiocyanates treated oilseed rape plantlets was deduced from increment of percentage of electrolyte leakage and from accumulation of hydrogen peroxide. Results showed that the PAL activity was significantly correlated to the contents of phenolic compounds in response to isothiocyanates. Results also showed that GST activity was induced in oilseed rape plantlets in response to exposure to 1mM isothiocyanate. Results suggested that production of total phenolic compound was not the only means of detoxifying in the oilseed rape plantlets and glutathione conjugation was also involved in the defense response to toxification in oilseed rape.

This paper represents a comparative study of total phenol and flavonoid contents، antioxidant and antimicrobial activities of the methanolic extracts of three Trigonella species، namely T. disperma، T. teheranica and T. subnervis. Total phenol and flavonoid contents were determined by Folin Ciocalteu and Aluminum chloride colorimertric methods، respectively. DPPH free radical scavenging assay was used to evaluate antioxidant activity. In addition، antibacterial activities of the extracts against six gram positive and negative bacteria were studied by disc diffusion method. Total phenol and flavonoid contents varied from respectively 8 ± 0. 28 to 22. 2 ± 1. 4 mg/g dw and 5. 23 ± 0. 33 to 10. 48 ± 1. 2 mg/g dw، in the studied species. In addition، the species showed high antioxidant capacities. However، there were no significant differences between their IC50 values. The highest scavenging potency of DPPH free radical was observed in T. subenervis with IC50 = 0. 123 ± 0. 006 mg/ml. All three species، especially T. teheranica showed remarkable antimicrobial activity against some studied bacteria.

The northern forests of Iran are Tertiary relicts and large parts of its lowlands have been destroyed due to human interference. However، only some small patches of these forests have remained yet which deserve a high value of conservation policies. Noor and Sisangan forests in Mazandaran lowlands were investigated with a phytosociological approach. The phytosociological data were collected from 55 relevés and classified using modified TWINSPAN in the JUICE software. Four vegetation unites were described: Celtis australis-Buxus hyrcana، Fraxinus excelsior subsp. coriariifolia-Cardamine tenera، Populus caspica-Alnus subcordata and Parrotia persica-Carpinus betulus. Exhaustive investigation of all diagnostic species of described communities in the Hyrcanian forest، clarified the connectivity of the studied vegetation unites with two major alliances، Parrotio-Carpinion and Alnion subcordatae. Obviously، the final decision on the syntaxonomical situation of the associations would be impossible without more a comprehensive investigation on the whole Hyrcanian area.