Extended Abstract

Introduction

That is required to gain maximum plant growth and yield by management of agronomy under water deficit stress. Silicon and ACC deaminase producing bacteria decline the destructive effects of water deficit stress. The aim of this study was to investigate the effect of silicon application on plant tolerance and the effect of ACC-deaminase-producing bacteria in reducing the effects of water deficit stress.

Methods and material

Experiment was done as split plot based on randomized complete block design in three replications. The main plots consisted of three irrigation regimes including irrigation intervals based on 60, 90 and 120 mm cumulative evaporation from Class-A evaporation pan and sub-plots consisting of four levels: 1- control (no silicon and bacterial inoculation), 2- silicon application (20 kg ha-1 from potassium silicate source by soil application) 3- inoculation of ACC-deaminase-producing bacterium (preparation of bacterial inoculum with 107 CFU ml-1 population or colony forming unit ml-1), 4- silicon application (20 kg ha-1 soil from potassium silicate source) and inoculation of ACC-deaminase (Bacillus simplex UT1). Wheat seed was Chamran and its quantitative traits such as grain and biological yield, 1000-grain weight, number of grains per spike, number of spikes per square meter and quality traits, concentration of silicon and total absorbed silicon were measured. Statistical analysis was performed using SAS v.9.2 and LSD test.

Results and Discussion

Analysis of variance showed that the main effect of drought stress on grain yield, biological yield and harvest index was significant at 1, 1 and 5%, respectively. Irrigation after 120 mm of cumulative evaporation from class-A evaporation pan resulted in yield of 4705 kg ha-1 which showed a decrease of 46.1% compared to control. The results showed that wheat grain yield was 6507 kg ha-1 in without silicon application and ACC-deaminase-producing bacteria, while the highest grain yield was in associated application of silicon and ACC-deaminase-treated bacteria with 7398 kg ha-1, and this increase was statistically significant by 13.7% with the use of silicon and bacteria compared to the control. Under water deficit stress conditions, even application of ACC-deaminase-producing bacteria alone and application of silicon alone increased grain yield by 9.92% and 8.73%, respectively. Among the treatments, the best results under deficit irrigation conditions was obtained by combined application of silicon and ACC-deaminase-producing bacteria. In general, ACC-deaminase-producing bacteria, due to the presence of plant growth-promoting compounds such as nutrient elements, phytohormones and enzymes, can improve plant growth characteristics and nutrient absorption. Also, silicon and ACC-deaminase-producing bacteria improved growth parameters due to its role in increasing photosynthesis respiration, cell membrane permeability and root architecture.

Conclusion

In general, the combined use of silicon and ACC-deaminase-producing bacteria with control treatment reduced ethylene concentration under drought stress and improved absorption of elements concentrations in wheat. Based on the results of this study, in conditions of drought stress, the use of silicon is recommended, especially with the inoculation of bacteria that produce the enzyme ACC-deminase.

Key words: Irrigation, stress ethylene, silicon, nutrient elements, yield

That is required to gain maximum plant growth and yield by management of agronomy under water deficit stress. Silicon and ACC deaminase producing bacteria decline the destructive effects of water deficit stress. The aim of this study was to investigate the effect of silicon application on plant tolerance and the effect of ACC-deaminase-producing bacteria in reducing the effects of water deficit stress.

Methods and material

Experiment was done as split plot based on randomized complete block design in three replications. The main plots consisted of three irrigation regimes including irrigation intervals based on 60, 90 and 120 mm cumulative evaporation from Class-A evaporation pan and sub-plots consisting of four levels: 1- control (no silicon and bacterial inoculation), 2- silicon application (20 kg ha-1 from potassium silicate source by soil application) 3- inoculation of ACC-deaminase-producing bacterium (preparation of bacterial inoculum with 107 CFU ml-1 population or colony forming unit ml-1), 4- silicon application (20 kg ha-1 soil from potassium silicate source) and inoculation of ACC-deaminase (Bacillus simplex UT1). Wheat seed was Chamran and its quantitative traits such as grain and biological yield, 1000-grain weight, number of grains per spike, number of spikes per square meter and quality traits, concentration of silicon and total absorbed silicon were measured. Statistical analysis was performed using SAS v.9.2 and LSD test.

Results and Discussion

Analysis of variance showed that the main effect of drought stress on grain yield, biological yield and harvest index was significant at 1, 1 and 5%, respectively. Irrigation after 120 mm of cumulative evaporation from class-A evaporation pan resulted in yield of 4705 kg ha-1 which showed a decrease of 46.1% compared to control. The results showed that wheat grain yield was 6507 kg ha-1 in without silicon application and ACC-deaminase-producing bacteria, while the highest grain yield was in associated application of silicon and ACC-deaminase-treated bacteria with 7398 kg ha-1, and this increase was statistically significant by 13.7% with the use of silicon and bacteria compared to the control. Under water deficit stress conditions, even application of ACC-deaminase-producing bacteria alone and application of silicon alone increased grain yield by 9.92% and 8.73%, respectively. Among the treatments, the best results under deficit irrigation conditions was obtained by combined application of silicon and ACC-deaminase-producing bacteria. In general, ACC-deaminase-producing bacteria, due to the presence of plant growth-promoting compounds such as nutrient elements, phytohormones and enzymes, can improve plant growth characteristics and nutrient absorption. Also, silicon and ACC-deaminase-producing bacteria improved growth parameters due to its role in increasing photosynthesis respiration, cell membrane permeability and root architecture.

Conclusion

In general, the combined use of silicon and ACC-deaminase-producing bacteria with control treatment reduced ethylene concentration under drought stress and improved absorption of elements concentrations in wheat. Based on the results of this study, in conditions of drought stress, the use of silicon is recommended, especially with the inoculation of bacteria that produce the enzyme ACC-deminase.

Key words: Irrigation, stress ethylene, silicon, nutrient elements, yield