تاثیر مدت زمان و عمق دفن بر شکست خواب و درصد جوانه‌زنی بذور علف هرز میاگروم (myagrum perfoliatum l.)

میاگروم با نام علمی myagrum perfoliatum l. علف هرزی زمستانه است که در ایران و بویژه در استان کرمانشاه در محصولات زمستانه و پاییزه مانند گندم و جو مشکل‌ساز شده است و جمعیت آن رو به افزایش است اما متاسفانه علی‌رغم خسارت و پراکنش بالای میاگروم، مطالعات زیادی راجع به اکولوژی، فیزیولوژی و بیولوژی آن انجام نشده است. بنابراین این آزمایش در سال زراعی 941393 با هدف بررسی تاثیر مدت زمان و عمق دفن بذر بر شکست خواب و جوانه­زنی بذور علف هرز میاگروم به­صورت فاکتوریل در قالب طرح بلوک­های کامل تصادفی با چهار تکرار در مزرعه تحقیقاتی پردیس کشاورزی و منابع طبیعی دانشگاه رازی کرمانشاه اجرا شد. فاکتور­های مورد بررسی در آزمایش شامل مدت زمان دفن بذور در خاک (270، 360 و 420 روز)، عمق دفن بذور (صفر، 5، 10، 20 و 40 سانتی­متر)، دما (25 درجه سانتی­گراد ثابت، 5/10 و 10/20 درجه سانتی­گراد متغیر) و نور (نور و تاریکی) بودند. نتایج نشان داد که درصد جوانه­زنی بذور علف هرز میاگروم در نور و تاریکی اختلاف معنی­داری نداشتند، همچنین زمان دفن بذور، دما، عمق دفن بذور و اثر متقابل زمان دفن*دما اثر معنی­داری (p≤0.01) بر درصد جوانه­زنی بذور گذاشت. بالاترین درصد جوانه­زنی (69/5 درصد) با گذشت زمان دفن 420 روز و در دمای 20/10 درجه سانتی­گراد متغیر مشاهده شد، همچنین در سطح خاک و با افزایش عمق دفن بذور (بیشتر از 5 سانتی­متر) زنده مانی و درصد جوانه­زنی بذور در مقایسه با عمق 5 سانتی­متری خاک کاهش یافت (به­ترتیب 50/49، 51/76، 54/36 و 67/99 درصد کاهش درصد جوانه­زنی در عمق 0، 10، 20 و 40 سانتی­متری خاک در مقایسه با عمق 5 سانتی­متری خاک) زیرا بذور برای جوانه­زنی به شرایط خاص رطوبتی و دمایی نیاز دارند که بنابر نتایچ به­دست آمده این شرایط در عمق 5 سانتی­متری خاک وجود داشته است پس می­توان نتیجه گرفت که انجام شخم عمیق و رفتن بذور به اعماق ممکن است به مدیریت این علف هرز کمک کند.

Effect of Time and Burial Depth on Breaking Seed Dormancy and Percentage of Germination of Myagrum (Myagrum perfoliatum L.) Weed Seeds

Introduction: The internal factors of seeds and the conditions outside the seeds can affect the germination and emergence of seeds. In some cases, environmental conditions are suitable for seed to germinate, while the seeds do no seed dormancy which is regarded to be one of the factors in seed survival. Seeds are exposed to different conditions of temperature fluctuations, moisture fluctuations, activity of microorganisms, etc. by being located at different depths of the soil. For instance, seeds that are located in the surface layers of the soil are more exposed to soil moisture fluctuations, which may also affect their dormancy. The results of various experiments have shown that in addition to the depth of burial of seeds, their burial time also affects their germination. Due to the fact that no experiments have been performed on the germination of myagrum weed seeds in this field, this study was conducted to investigate the effect of time and burial depth on breaking seed dormancy and percentage of germination of myagrum.Materials and Methods: This study aimed to investigate the effect of burial time and burial depth on breaking seed dormancy and germination of myagrum seeds in factorial experiment based on a randomized complete block design with 4 replications in the research farm of Razi University of Kermanshah in 20142015. Experimental factors include burial time (270, 360 and 420 days), burial depth (0, 5, 10, 20 and 40 cm), temperature (25 ° C, 5/10 and 10/20 °C variable temperature) and light (light and dark). In June 2014, myagrum seeds were collected from plants that had become mature and were in the full mature stage stored in plastic nylon at 25 °C until the seeds were tested. At the beginning of the experiment, the seeds were packed in lace bags that had small pores from which the seeds could not exit and then placed at different depths of the farm soil. 340 seeds were placed in each lace bag. The lace bags were such that the seeds were exposed to the moisture, temperature and chemical regimes of the soil. To make it easier to exit the lace bags from the soil, a thread was attached to each bag that was placed on the soil surface. After each level of burial time in the soil (270, 360 and 420 days), lace bags were exited from different depths. Firstly, the number of germinated seeds in each lace bag was counted and the germination percentage was calculated. Germinated seeds were then removed from the bags and the residual of seeds was transferred to the Agriculture Laboratory of the Agricultural and Natural Resources Campus of Razi University. The results of Mondani et al. (16) study showed that myagrum seeds have physiological dormancy and mechanical dormancy due to hard outer shell. Therefore, seeds do not germinate included damaged seeds and seeds had physiological dormancy and mechanical dormancy. Extracted seeds (not germinated seeds) from different depths in each burial time were disinfected in sodium hypochlorite solution (2%) for ten minutes. Then, to ensure the viability of the seeds, a number of seeds of any depth were randomly selected and tested using tetrazolium solution (0.1%). The appearance of red color indicated the existence of respiration and viability of the seeds (13). To remove the mechanical dormancy caused by the hard outer shell in the seeds, the outer shell of the seeds was removed and then the seeds were placed in sterile petri dish with a diameter of 7 cm containing Whatman No. 1 filter paper and 5 ml of distilled water (30 seeds were placed in per petri dish) and to prevent water evaporation, the petri dishes were closed with parafilm. The petri dishes were then exposed to different temperatures (25 °C, 5/10 and 10/20 °C variable temperature) inside the germinator and in light and dark conditions. To exert the effect of darkness, petri dishes were wrapped in an aluminum foil. After 14 days, the number of germinated seeds in each petri dish was counted. Germination criterion was visible root exit. Finally, data analysis was performed by SAS (version 9.4) software and mean comparisons were performed based on Duncan at 5% probability.Results and Discussion: The results showed the germination percentage of myagrum weed seeds in light and dark were not significantly difference, and also seed burial time, temperature, burial depth and burial time * temperature interaction had a significant effect (p ≤ 0.01) on the germination percentage. The highest germination percentage was observed after 420 days of burial at a variable temperature of 10/20 °C. Also, at the soil surface and with the increasing seed burial depth (more than 5 cm) the survival and seed germination percentage decreased compared to soil depth of 5 cm because seeds need special moisture and temperature conditions for germination. According to the results, these conditions existed at a depth of 5 cm in the soil, so it can be concluded that deep plowing and going deep seeds may help to manage this weed.Conclusion: Considering that the highest germination percentage was observed in the temperature regime of 10/20 °C, it can be assumed that this weed can be problematic in summer and autumn crops because this temperature range synchronizes in late winter and early spring. On the other hand, it is possible to control this weed in wheat fields. In fact, in wheat fields, herbicides such as 2,4D and MCPA are used to control broadleaf weeds in late March and early April, when the temperature is about 10/20 ° C and the time of germination and emergence of myagrum is used. However, if this weed appears in chickpea fields, it is difficult to control because there is no specific herbicide in chickpea fields to control broadleaf weeds, including myagrum. Also, as the depth of burial increased, the germination percentage of the seeds decreased, so deep plowing and deepening of the seeds may help to manage this weed.