تاثیر برخی عوامل محیطی بر جوانه‌زنی و رشد گیاهچه هرز تاتوره تماشایی (. Datura Innoxia Mill)

به‌منظور بررسی عوامل محیطی بر مراحل جوانه زنی علف هرز تاتوره تماشایی چهار آزمایش جداگانه در قالب طرح کاملا تصادفی با 6 تکرار در سال 1396 انجام شد. تیمارهای آزمایش شامل سطوح مختلف شوری و خشکی در 6 سطح (صفر، 0.2-، 0.4-، 0.6-، 0.8- و 1- مگاپاسکال) و اثر اسیدیته با استفاده از محلول های بافر با اسیدیته تنظیم شده 4 تا 9 موردبررسی قرار گرفتند. برای مطالعه عمق کاشت بذر روی سبز شدن بذور هر گیاه در اعماق صفر، 2، 4، 6، 8 و 10 سانتیمتری قرار گرفتند. نتایج نشان داد که با افزایش شدت تنش شوری و خشکی به صورت معنی داری از درصد جوانه زنی در سطح احتمال (p <0.05) کاسته شد. در برازش مدل سه پارامتری، رابطه بین سطوح مختلف تنش با درصد جوانه زنی، پارامتر x50 مدل نشان داد که تنش شوری و خشکی به ترتیب در پتانسیل های 0.39- و 0.27- مگاپاسکال منجر به کاهش 50 درصدی حداکثر جوانه زنی شدند که نشان دهنده تاثیر بیشتر تنش خشکی بر تاتوره می باشد. اسیدیته مطلوب برای جوانه­زنی تاتوره 6 بود و با افزایش ph از درصد جوانه زنی کاسته شد. بیشترین درصد سبز شدن بذور تاتوره در سطح خاک 73.33 درصد بودند و با افزایش عمق خاک درصد سبز شدن گیاهچه کاهش یافت. تنها 5 درصد از بذور قادر به سبز شدن از عمق 8 سانتی متر سبز شدند. با توجه به اینکه گیاه تاتوره به برخی از عوامل محیطی مورد مطالعه مقاوم هست می تواند به عنوان یک علف هرز جدی در آینده در مزارع و باغات حضور داشته باشد. باشناخت اکولوژی و بیولوژی بذر تاتوره می­توان راهکارهای جدیدی با توجه به پیش بینی الگوی جوانه زنی و سبز شدن این علف هرز در جهت توسعه مدیریت تلفیقی ارائه داد.

Effects of salinity and drought stress on germination and seedling Datura innoxia Mill.

Introduction Seed germination is first critical and the most sensitive step in the life cycle of plants. Germination of weeds has an important role in its establishment in an agricultural and seed germination and seedling establishment are critical and important stages in plant life cycle caused by environmental factors such as salinity, humidity, temperature, light and pH soil is regulated. If a plant that can show greater resistance to environmental stresses in the germination stage will be able to make its first course more successful. Usually, the most susceptibility to stress in the plant life cycle occurs during germination and at the beginning of seedling. Material and method Datura innoxia L. seeds were prepared from Agricultural Research Bahar University, Hamedan, Iran. Seeds were sterilized with 5% sodium hypochlorite solution for 5 min. Followed by washing with distilled water. Therefore, they were transferred to 9 cm diameter sterilized petri plate containing single layer of filter paper. Salinity stress was induced by using sodium chloride (NaCl) and drought stress by using Polyethylene Glycol (PEG6000). Five ml NaCl solution and PEG6000 (0.2, 0.4, 0.6, 0.8, 1 MPa) were added in different petri plates. The control or (0) contained five ml of sterile distilled water. Each treatment was maintained in six replicas along with control. To study the effect of pH on germination, pH solutions with acidity of 4 to 9, and depth effect on seeds cultivated at depths of 0, 2, 4, 6, 8 and 10 cm. Germination was carried out in a germination chamber with a regime of 24 h dark at 25 °C. Results and discussion Analysis of variance of the effects of salinity and drought stress on seed germination of D. innoxia suggested that these treatments made significant changes at (p < 0.05). The reduction in seed germination was proportional to the increasing concentration of NaCl and PEG. Maximum retardation was noted at highest NaCl concentration and PEG 6000 (1 MPa). With the increasing intensity of drought and salinity from 0 to 1 MPa D. innoxia germination percentage of 100 percent respectively compared to control was reduced. Fitting of threeparameter logistic model, provided a successful estimation of the relationship between salt and drought stress levels and germination percentage of D. innoxia as well as germination speed. This model showed that salinity and drought stress at 0.39 and –0.27 MPa, respectively caused 50% reduction in maximum germination percentage of D. innoxia. In addition 50% decrease in germination speed caused by salinity and drought stress, were observed in 0.33 and 0.28 MPa, respectively. The optimum pH for germination was 7 and the pH increased by decreasing the germination percentage. The highest percentage of emergence of in surface soil seeds was 73.33% and with increasing soil depth the percentage of seedling emergence decreased. Only 3% of the seeds are able to germinate from a depth of 8 cm.   Conclusion This research revealed that D. innoxia differed significantly in its response to salt and drought stress. D. innoxia is more sensitive to drought stress at germination stage. However, at early growth stage both salt induced osmotic stress and Na toxicity reduced growth. For better management of this weed in farms and gardens, we can use tillage operations so that seeds are transmitted at a depth of more than 8 cm and can prevent the emergence of this weed. In alkaline environments, germination of the plant decreases.