فصلنامه زیست شناسی گیاهی ایران
سال سوم شماره 4 (پیاپی 10، زمستان 1390)

Fluoride is a toxic solution for the nature and enters environment from different sources. Aluminum industry is the most important source of fluoride which empties to the nature as sodium fluoride, hydrogen fluoride, gas components of fluoride and fluoride particles causing damaging effects on plants, animals and the humans. In this research, toxic effect of sodium fluoride as a nature pollutant has been examined on bean Phaseolus vulgaris. At first, bean seeds were exposed to different concentrations of sodium fluoride (0.2, 0.5, 1 and 2 mg/100 cc water) while three other treatments put aside because of high toxicity of the solution and anti-germinative effects in these concentrations. In the second stage, we applied new solutions with concentrations of 0.5, 0.8 and 1.2 mg/l sodium fluoride for germination and tilling the seeds, and just watered the controls. In vegetative phase, damaging effects of NaF during daily irrigation were observed as necrosis, chlorosis and wounds on leaf blade, early senescence and plants fading. Increase in root and shoot length and decrease in generation rate and root ramification also could be attributed to NaF. Delay in transition of shoot apex from vegetation phase to generation phase was another observed effect of fluoride treatment.

Papaver pseudo-orientale in section Oxytona of Papaver genus is an important source of alkaloids such as isothebaine. In this research, callus production and regeneration of this species from hipocotyl-cotyledon explants under in vitro conditions were investigated on Murashige and Skoog (MS) and Gamborg (B5) basic media supplemented with different levels of Kinetin (Kin), Benzyladenine (BA) and Naphthalene acetic acid (NAA) at 16-h photoperiod and 20 °C. Analysis of variance showed significant (P<0.01) differences between different culture media for callus induction rate, callus weight, shoot induction rate, shoot weight, root induction rate and root weight. Results showed that the proper media for P. pseudo-orientale callogenesis were MS medium supplemented with 0.5 mg/l BA and 0.5 mg/l NAA and B5 medium supplemented with 0.5 mg/l Kin and 1.0 mg/l NAA and the most favorable medium for regeneration of the studied species was B5 medium supplemented with 0.5 mg/l Kin and 0.5 mg/l NAA.

Some plant phenolics as allelochemicals take part in allelopathy and affect seed germination and seed growth, thereby reduce plant productivity. On the other hand, these allelochemicals maybe used to control pests, plant pathogens and eradication of weeds. In the present study, the effects of different concentrations of coumarin (0, 0.05, 0.5, 5 and 10 Mm) on seed germination, seedling growth, pigments content, activity of catalase and guiacol peroxidase were investigated. Pigments content was measured spectrophotometrically, catalase and guiacol peroxidase activities were determined at 240 and 436 nm. Coumarin reduced seed germination and seedling growth of canola Hyola 401 cultivar. Cholorophyll content was also decreased in the presence of this phenolic compound. Low molecular weight antioxidants, such as carotenoids and anthocyanins, were increased by coumarin. At higher concentrations of coumarin, catalase activity was not decreased significantly. Guaicol peroxidase, an antioxidant enzyme showed a significantly increase in activity in the presence of this phenolic compound. We concluded that this allelochemicals investigation could result in the development of herbicides with less adverse effect on environment and ecosystem. The presence of some phenolic compounds can reduced canola yield therefore, elimination of weeds, containing these compound are very important, from allelopathic point of view, to enhance canola production.

Aut-ecological studies provide basic and essential information for rangeland and ecosystem management. Aut-ecological study of a range plant named Lolium rigidum was accomplished in Mazandaran province. Geographical distribution, phenology, co-occurring species, dryness index, physicochemical soil parameters, climatical studies and other effective environmental factors on distribution of this species including altitudinal modifications in nine ecological sites in Mazandaran province were investigated. Correlation between quantitative plant vegetation, soil and climatic characters of each location was evaluated by Pearson correlation index. The results showed that favorite elevation for this species is between -22 to 1700 meters above sea level. The studied plants grew with higher frequency in diverse environments such as road sides and the irrigation canals. This species is resistant to cold and harsh condition of alpine habitats. Results showed that due to the wide compatibility with edaphic and climatic conditions, Lolium perenne could be found in different regions.

Populus deltoides is an important species of Salicaceae family and is distributed in Northern America. This species has been cultured widely in Northern provinces of Iran during recent decades. Survival and growth response of P. deltoides seedlings to flood stress was examined at three levels of: control, shallow flooded (3 cm) and deep flooded (16 cm) in a completely randomized design for 120 days. The experiment was set up under outdoor conditions at the campus of Natural Resources of Tarbiat Modares University, Noor, Iran. P. deltoides survival in the control and the flooding groups did not differ statistically and was more than 90%. By increasing flooding depth, height growth decreased but there was no differences between shallow flooding and the control. Flooding produced adventitious roots and with increasing flooding depth, adventitious root biomass enhanced. On the other hand, flooding decreased collar diameter growth, leaf area, specific leaf area, root length, root biomass, and total dry biomass of seedlings. Overall, the results showed that P. deltoides was tolerant to flooding and can be used for restoration of plains exposure to periodic floods like plateau and riparian areas.

Effects of different concentrations of herbicide trifluralin on physiological characters and growth of root and shoot, total protein, proline and free amino acids content in mycorrhizal (M) and non-mycorrhizal (NM) sunflower plants were studied under greenhouse conditions. Six different concentrations of trifluralin (0, 5, 10, 15, 20, 25 ppm) were used. The obtained results of 5-week-old plants indicated that the length of shoots and roots as well as their fresh and dry weight decreased in herbicide treated plants, and this was significant in high herbicide concentrations (15, 20, 25 ppm). Also, growth inhibition in M plants was less obvious than NM plants. The amounts of total protein content decreased both in roots and shoots according to the amount of applied herbicide. Total protein contents of roots were higher in M than NM plants. By increasing herbicide concentrations, proline and free amino acids content in shoots and roots increased. According to these results, it is suggested that this fungus (Glomus versiforme) can help sunflower plants to tolerate trifluralin toxicity.

The effect of paraquat as a pestiside, inducer of oxidative stress, has been investigated on a unicellular green alga Dunalilella during 24 h, pretreated with 14ºC temperature, Buthionine sulfoximine (BSO) and L-galactonic acid -lactone (GAL). High decrease in pigment contents (chlorophylls and β-carotene), fresh weight of the cells and depletion of ascorbate and glutathione pools that was followed by bleaching and dying the cells, were seen after treatment with paraquat under control temperature. Cold pretreatment caused an increase in the fresh weight of the cells and also Chlorophyll a and b contents. In addition, staying high β-carotene content, β-carotene/chl and no depletion of ascorbate and glutathione pools after paraquat treatment were seen. No bleaching was observed in the cold pretreated samples and all suspensions remained green. However, pretreated sample with GAL (ascorbate precursor substrate) in control temperature, showed a big increase in Chl a, b and a small amount of remained reduced ascorbate in a few alive cells, after papraquat treatment, but the complete depletion in glutathione pool, a great increase in oxidized ascorbate and the decrease of cell numbers basically, have been observed and resulted in the bleaching of cell suspension. Pretreatment with BSO (inhibitor of glutathione synthesis) caused bleaching and dying the cells under control temperature after paraquat addition, but it inhibited glutathione increase in cold pretreated cells before adding the paraquat. This pretreatment resulted in keeping the glutathione in low level after adding the paraquat however, this sample remained green. It seems that, cold pretreatment basically and pretreatment with GAL nearly, could induce antioxidant system but the green cell suspensions were seen just in cold pretreated samples under papraquat treatment.