نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی دکتری علوم‌زیستی جنگل،دانشکده منابع طبیعی، دانشگاه لرستان، خرم‌آباد،ایران
2 گروه جنگلداری، دانشکده کشاورزی و منابع طبیعی، دانشگاه لرستان، لرستان، ایران
3 دانشیار، گروه مرتع و آبخیزداری(مهندسی طبیعت)، دانشکده منابع طبیعی دانشگاه دانشگاه فسا، فسا، ایران
4 دکترای علوم و اکولوژی جنگل، دانشکده منابع طبیعی، دانشگاه لرستان، خرم‌آباد، ایران
5 دکترای فیزیولوؤی تولید وپس از برداشت گیاهان باغبانی، دانشکده کشاورزی، دانشگاه لرستان، خرم‌آباد، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: Soil contamination with petroleum hydrocarbons is one of the most serious environmental challenges worldwide, posing significant threats to human health and to the structure and function of ecosystems. Bioremediation, an approach that encompasses both phytoremediation (the direct use of plants) and the application of microorganisms, is widely recognized as a sustainable, low-cost, and environmentally friendly strategy for restoring petroleum-contaminated soils. Among candidate species, the native forest tree Pistacia atlantica Desf. (Baneh), Plant growth-promoting bacteria are known to alleviate the adverse effects of petroleum hydrocarbon contamination on plants through several complementary mechanisms, including the degradation of hydrocarbon compounds, the production of auxins that stimulate root development, the reduction of stress-induced ethylene levels in host plants through 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and the production of siderophores that enhance iron availability under stress conditions. In the present study, the plant growth-promoting bacterium Pseudomonas putida strain RO7 was selected for its broad spectrum of such growth-promoting mechanisms. Accordingly, this study was conducted with the aim of evaluating the effects of different levels of crude oil contamination, alone and in combination with inoculation with Pseudomonas putida, on the survival and morphological traits of one-year-old Pistacia atlantica seedlings under controlled greenhouse conditions.
Materials and methods: The experiment was conducted as a factorial trial based on a completely randomized design with three replications. The two experimental factors were crude oil contamination at four levels (0, 10, 25, and 50% w/w, based on the dry weight of the soil) and bacterial inoculation at two levels (inoculated with Pseudomonas putida strain RO7 and non-inoculated control). One-year-old Pistacia atlantica seedlings had been artificially contaminated with crude oil at the designated levels and, where applicable, inoculated with the bacterial suspension. The seedlings were maintained under greenhouse conditions with irrigation scheduled according to the field capacity of the soil to avoid confounding effects of water stress. At the end of the growth period, seedling survival percentage, plant height, root collar diameter, root length, root volume, number of leaves, and the fresh and dry weight of the root, stem, and leaf organs measured. The to two-way analysis of variance used to determine the main effects of contamination level and bacterial inoculation as well as their interaction, and means were compared using Tukey's Honestly Significant Difference (HSD) test. probability levels.
Results: Increasing levels of crude oil contamination significantly reduced seedling survival and most of the measured morphological traits. the greatest plant height (32.8 cm) and the greatest root collar diameter (0.894 mm) were both recorded in the non-contaminated control treatment in the presence of bacterial inoculation, indicating that the bacterium also enhanced growth under stress-free conditions. Root volume was significantly affected by contamination level, bacterial inoculation, and their interaction; notably, bacterial inoculation at the highest contamination level maintained root volume at approximately 61% of that recorded in the non-inoculated, non-contaminated control treatment, indicating substantial mitigation of root growth suppression under severe oil contamination. In contrast, the effect of bacterial inoculation on the fresh and dry weight of stems and leaves was not statistically significant, suggesting that the protective and growth-promoting effects of Pseudomonas putida were concentrated predominantly on belowground organs (roots) rather than on aboveground organs (stems and leaves).
Conclusion: The findings of this study demonstrate that Pseudomonas putida possesses considerable potential to enhance the survival and improve the morphological traits of Pistacia atlantica seedlings, with this protective effect being most pronounced at the highest level of crude oil contamination. Since the present results were obtained under controlled greenhouse conditions, further field-scale studies are recommended to confirm the stability and applicability of these findings under natural environmental conditions.
کلیدواژه‌ها [English]
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