كليدواژه :
جمعيت باكتري , باكتري Bacillus subtilis , ريزوباكتر‌‌هاي محرك رشد گياه , غلظت فسفر , كشت بدون‌خاك
چكيده فارسي :
آزمايشي گلخانه‌اي (به صورت فاكتوريل و در قالب طرح كاملاً تصادفي) به منظور ارزيابي اثر باكتري UTB96 Bacillus subtilis و غلظت‌هاي مختلف فسفر محلول غذايي (12.5، 25، 37.5، 50 و 62.5 ميلي گرم بر ليتر) بر عملكرد و ويژگيهاي فيزيولوژيكي كاهو لولوروسا در 3 تكرار انجام شد. اثر متقابل UTB96 B. subtilis و غلظت‌هاي مختلف فسفر محلول غذايي نشان داد كه همانند تيمار 50 ميلي گرم بر ليتر، كاهش 25 درصدي مصرف فسفر (غلظت 37.5 ميلي گرم بر ليتر) نيز در تيمار-هاي با تلقيح باكتريايي سبب بروز بالاترين مقادير نرخ فتوسنتز،CFU و كاهش 50 درصدي فسفر (غلظت 25 ميلي گرم بر ليتر) سبب افزايش جذب فسفر بافت‌هاي ريشه و ساقه كاهو لولوروسا گرديد. عملكرد گياهان با تيمار 37.5 ميلي گرم بر ليتر فسفر و تلقيح باكتريايي (BS1P3) بيشتر از تيمار 50 ميلي گرم بر ليتر فسفر و بدون تلقيح باكتريايي (BS0P4) بوده است. بنابراين نتايج اين مطالعه نشان داد كه با بهره‌گيري از باكتري UTB96 B. subtilis نه تنها مي توان سبب افزايش عملكرد محصولات گلخانه‌اي در شرايط كشت بدون خاك شد، بلكه مي توان با كاهش 25 درصدي مصرف كود‌هاي فسفره نتايج مشابه با تيمار‌هاي استاندارد را هم انتظار داشت. بنابراين اين يافته ها گام موثري در كاهش مصرف كود‌هاي گران قيمت فسفره و كاهش آلودگي‌هاي زيست محيطي مي‌باشد.
چكيده لاتين :
Introduction: Phosphorus is the second limiting element of plant yield after nitrogen. Rock phosphate is a non-renewable resource. Global data shows that by 2050 the requirement for P fertilizers will increase by 50-100% and universal phosphate rock resources will be evacuated within the next 50-100 years (Cordell et al. 2009). Phosphate-solubilizing microorganisms such as bacteria are one of the most important tools for researchers in reducing of phosphorus fertilizers consumption in agriculture. Despite many studies on the effect of bacteria on physiological reactions and plant performance in soil culture, there are few reports on the effect of bacteria on these reactions in hydroponic culture. The aim of this study was to investigate the role of Bacillus subtilis on yield, photosynthetic properties and reducing of phosphorus fertilizers consumption in hydroponic culture.
Material and methods: The experiment was factorial based on a completely randomized design with three replicates. A greenhouse experiment was performed to evaluate the effect of Bacillus subtilis UTB96 and different concentrations of nutrient phosphorus (12.5, 25, 37.5, 50 and 62.5 mg L-1) on the yield, pigments and photosynthetic index, root-to-shoot phosphorus ratio and bacterial population. ‘Lollo Rosso’ lettuce seedlings were prepared under greenhouse conditions. Probio 96® biological fertilizer was used to inoculate the ‘Lollo Rosso’ lettuce seedlings at time of transplant by utilization a root dip method (with submergence for 5 min); then a repeated inoculation was conducted at 20 days after transplanting by watering 25 mL of the inoculums plant-1. Lettuce plants were grown in soilless culture with the Resh nutrient solution (Resh, 2012). P was added as KH2PO4 at the following concentrations of 12.5, 25, 37.5, 50, and 62.5 mg L-1. Photosynthetic indices were measured during growth and traits such as yield and physiological characteristics were measured at harvest time (50 days after transplanting). All data were statistically analyzed by analysis of variance (ANOVA) using the SAS 9.1 software (SAS Inc., Cary NC). Duncan’s multiple-range test was performed at p = 0.05 on each of the significant variables measured.
Results and discussion:
The mean comparisons showed that plants inoculated with bacteria had higher yields than uninoculated plants at all levels of phosphorus (Figure 3). Interaction data of bacteria and different concentrations of phosphorus in the nutrient solution showed that, like the 50 mg L-1 treatment, a 25% reduction in phosphorus consumption (37.5 mg/L) caused the highest photosynthesis rates in BS1P3 (Bacterial inoculated and 37.5 mg/L of phosphorus) and BS1P4 (bacterial inoculation and 50 mg/L phosphorus). The findings of this study clearly showed that as in the treatment of 50 mg/L, a reduction of 50% (25 mg L-1) and 25% of phosphorus consumption (concentration of 37.5 mg/L) in treatments with bacterial inoculation caused the highest values of phosphorus concentration in plant tissues and bacterial accumulation in the substrate, respectively (Table3).Today, the positive effects of these bacteria on plant yield to their effect on improving root growth (Rahi, 2016), increasing the absorption of nutrients such as phosphorus (Turom et al., 2007), the production of growth hormones such as auxin and gibberellin (Ruzzi and Aroca, 2015), attributed to the increase of photosynthetic pigments (Rahi, 2016) and the maintenance of photosynthetic efficiency (Wang et al., 2012). Therefore, according to the results of this study, the positive effects of this bacterium on photosynthetic indices may be due to their ability to increase phosphorus uptake in ‘Lollo Rosso’ lettuce, which indirectly affects root growth and photosynthetic efficiency and finally improved the above characteristics.
Conclusions: The results of this study showed that the use of Bacillus subtilis UTB96 biofertilizer improves nutrient uptake, increases the growth of greenhouse plants in hydroponic condition and reduces the phosphorus fertilizers consumption.
Keywords: Bacillus subtilis, plant growth-promoting rhizobacteria, soilless culture, phosphorus concentration, phosphate-solubilizing microorganisms and bacterial population.
