بررسي سطوح مختلف تنش شوري و خشكي بر خصوصيات جوانه زني و رشد اولية دانه رست گندم (Triticum aestivum L.) و علف هرز جودره (Hordeum spontaneum Koch)

Evaluation of the germination characteristics and early seedling growth of wheat (Triticum aestivum L.) and wild barley (Hordeum spontaneum Koch.) under salt and drought stress conditions

تنش شوري و خشكي يكي از عوامل محدودكننده در مراحل مختلف رشد و نمو گياهان هستند. به‌منظور ارزيابي جوانه ­زني، رشد اوليه گندم و جودره به تنش شوري و خشكي چهار آزمايش جداگانه در قالب طرح پايه كاملاً تصادفي با چهار تكرار در تابستان سال 1386 در آزمايشگاه تحقيقاتي گروه زراعت و اصلاح نباتات دانشكده كشاورزي دانشگاه بيرجند اجرا گرديد. سطوح مختلف تنش شوري و خشكي عبارت بودند از: پتانسيل‌هاي اسمزي صفر، 0.3 -، 5- ، 10- و 15- بار. نتايج اين تحقيق نشان داد كه با افزايش سطوح مختلف شوري و خشكي درصد جوانه ­زني، سرعت جوانه­ زني، وزن‌تر دانه­ رست، وزن تر ريشه­ چه، وزن تر ساقه­ چه، طول ريشه ­چه هر دو گياه كاهش يافت. نتايج مقايسه گروهي مستقل بين دو گياه نيز نشان داد كه درصد جوانه­ زني، سرعت جوانه­ زني، طول ريشه ­چه در جودره براثر تنش شوري و خشكي نسبت به گندم كاهش بيشتري داشت. در تنش شوري برازش مدل لجستيك سه پارامتري رابطه بين سطوح مختلف تنش و درصد جوانه ­زني گندم و جودره را به‌خوبي توجيه نمود. پارامتر X­50 مدل مذكور حاكي از كاهش 50 درصدي حداكثر جوانه­ زني گندم و جودره به ترتيب در پتانسيل­هاي اسمزي 10.82- و 6.40- بار بود. پارامتر X­50 در تنش خشكي براي گندم و جودره به ترتيب 12.63- و 5.20- بار به دست آمد. به‌طوركلي با مقايسه پارامتر X­50 و كمتر بودن آن در گياه جودره نسبت به گندم و ساير نتايج اين آزمايش مي‌توان گفت جودره به تنش شوري و خشكي حساسيت بيشتري نسبت به گندم دارد.

Introduction Germination is an important critical phenomenon which is influenced by weeds. This growth stage indicates the first stage as weed might be a competitor for ecological niche. This process of germination is influenced by several environmental factors such as light, temperature, salinity, pH and soil moisture. Knowledge about the pattern of germination and emergence of weed species can provide useful information for the future development of management strategies. Salt and drought stresses are among constraints for plant growth and development. Wild barley )Hordeum spontaneum Koch.) is an annual winter weed from poaceae family. It enumerates ancestor barley (Hordeum vulgare) which is sharply spreading in wheat fields in Iran. Climate conditions of Iran showed a dramatic spread of wild barley on wheat field, vital role of water potential on germination stage and no enough information about wild barley germination; This experiment was designed to evaluate the effect of salt and drought stresses on wild barley germination and early growth in comparison with wheat. Materials and Methods In order to assess the effects of different salt and drought stress levels on germination and early growth of wheat (Triticum aestivum) and wild barely (Hordeum spontaneum). Four experiments were conducted in growth chamber at the Advance Research Laboratory, Faculty of Agriculture, The University of Birjand. Treatments were four levels of drought and salt stress that created by PEG 6000 and NaCl respectively (-0.3, -5, -10 and -15 bars and distilled water as control). Salt stress were created using NaCl based on the Vant Hoff formula and drought stress were created using polyethylene glycol (PEG600), based on the Michel formula. The seeds were disinfected by sodium hypochlorite, 2% for a minute and then washed with distilled water. Four replications of 25-seeds of wheat and wild barely were placed in 9-cm Petri dishes lined with two discs of filter paper, moistened with either 10 ml demonized water or treatment solution when required. The Petri dishes were sealed with Parafilm to minimize evaporation and placed directly in the germinator. The number of germinated seeds recorded daily until the end of the germination test. Seeds were considered to have germinated when the radical emerged. Each treatment measured radical fresh weight, plumule fresh weight, radical length, plumule length A functional three-parameter logistic model was fitted to the germination values (percentage) obtained at different concentrations of NaCl or PEG for both wheat and wild barely using SigmaPlot . Results The results revealed that as increase in salt and drought stresses significantly decreased the percentage of germination, germination rate, seedling fresh weight, radicle fresh weight, plumule fresh weight and radicle and plumule length in wheat and wild barely. In order to, evaluation the effect inhibition of salt and drought stresses did apply orthogonal contrast between wheat and wild barley on percentage germination, germination rate, radical length and seedling fresh weight. Orthogonal comparison in two stresses showed that percentage of germination, germination rate, root length and seedling fresh weight of wild barely decreased more than wheat. The functional three-parameter logistic model showed that, salinity at -10.82 and -6.40 bar, respectively caused 50 percent maximum germination percentage of wheat and wild barley and drought stresses at -12.82 and -5.20 bar respectively, caused 50 percent maximum germination percentage of wheat and wild barley. Decreasing in germination rate in salt and drought stresses were similar to germination percentage. Decrease of germination rate was recorded 76.08 and 100 % in salt stress in wheat and wild barely respectively, and 74.60 and 100 % respectively in wheat and wild barely in drought stress. Conclusion Overall, result showed that wild barely was more sensitive to salt and drought stresses as compared to the wheat.