بررسی پتانسیل عملکرد ژنوتیپ‌های ارزن معمولی (Panicum miliaceum L.) تحت شرایط نرمال و تنش رطوبتی

Introduction
Common millet (Panicum miliaceum L.) is a cereal plant cultivated for its grain, mostly in semi-arid regions of Iran. It is a warm-season and C4 grass with higher water use efficiency than C3 plants, short growing season, low moisture requirement, relatively high drought resistance and is capable of producing food or feed where other grain crops would fail. Water resources deficit and drought stress is becoming a major threat to plant productivity loss in agricultural systems therefore optimum use of limited water resources and seasonal scattered rainfall and water use efficiency is necessary. Drought stress leads to lower growth, yield and yield components in pearl millet. Super ab‌sorbent polymers have a great importance for their role in increase of absorption capacity and saving water in the soil and to combat water shortage conditions. The water holding capacity of super ab‌sorbent polymers helps to keep plants from sitting in water logged soil in times of excess moisture. Then, as moisture is needed, super ab‌sorbent polymers release moisture back into the root zone helping to maintain consistent soil moisture. Positive impact of super absorbent polymers on growth and yield of soybean and corn under water limited condition have been reported. The aim of this study was to evaluate the use of different levels of water deficit and super absorbent polymers on morphological and physiological characteristics of millet ecotypes.
Material and methods
The experiment was carried out during spring and summer of 2013 in Faculty of agriculture research field of Shahid Bahonar University of Kerman (56º, 58'E; 30º, 15'N and 1754 m elevation). Soil type was a Sandy-loam, with pH 7.6 and mean annual precipitation of 150 mm. The experiment was carried out in a split plot arrangement based on RCBD design with three replications. Irrigation treatments included three levels: normal irrigation, drought stress with super absorbent application and drought stress were applied in main plots and Zahedan, Kahnooj, Ghale-ganj, Golbaf, p25 line and Pishahang Ecotypes as plant material were sown in sub plots. Irrigation intervals were conducted based on 50 and 100 mm evaporation from class A pan evaporation. Plants were harvested at the end of the growing season to determination of plant height, biological and grain yield. Ion leakage percent were measured based on method proposed by Zheng et al. (2008). Statistical analysis was done by MSTAT-C, Excel and SAS softwares and means were compared by Duncan’s multiple range test at 5% of probability level.
Results and discussion
The results showed that significantly increased were observed in stem length, grain and biological yield in super absorbent polymer application in comparison with the non-application in stress conditions. Stern et al. (1992) reported that the use of super absorbent polymers increased dry matter in wheat. The use of super absorbent decreased ion leakage that was consistent with the results of Harvey (2002). Pishahang cultivar had the higher biological yield in stress condition with super absorbent application compared to the other ecotypes of millet. Kahnooj ecotype in stem length and Ghale-ganj in grain yield significantly higher than the others. Kahnooj ecotype had the lower ionic leakage than the others. The results of this research revealed that Golbaf ecotype in drought stress and Ghale-ganj ecotype in drought by applying super absorbent conditions had significant performance. Application of super absorbent polymer increased 55.3% in grain yield compared to the non-application under drought stress. Stoker (1960) reported that drought stress leaded to increase in ionic leakage and reduced plant height and create short plants. Application of super absorbent polymers to reduce the devastating effects of drought on soybean and corn have been reported.
Conclusion
The super absorbent polymer increased grain yield compared to normal irrigation which indicating very positive and direct effect of this polymer in maintaining soil moisture nearby the plant roots and reducing the adverse effects of drought stress as well as increasing grain yield in millet ecotypes, therefore could be helpful materials for more utilization of plants potential in conditions and environments with water limitation.