Changes in chlorophyll content and fluorescence indices and some physiological traits of wheat under the influence of paclobutrazol and growth-promoting bacteria at different levels of irrigation

The use of growth-promoting bacteria increases vegetative growth, and with it, timely consumption with appropriate concentrations of growth retardant can play a role in the distribution of nutrients to the shoots and roots, and thus improve dehydration tolerance. For this purpose, in this study, the reaction of the new super wheat cultivar SHS022 under the conditions of irrigation regime with the use of growth-promoting bacteria and the application of growth retardant paclobutrazol were investigated. This research was conducted as a factorial split plot in the form of a randomized complete block design with three replications in Qom and Hamedan in the 2018-19 crop year. The first factor includes the amount of irrigation with three levels (irrigation at 40% of available moisture discharge throughout the growing season (control), normal irrigation up to pollination stage and irrigation at 60% available moisture discharge until seed maturity, irrigation at 40% Moisture release available up to pollination stage and cessation of irrigation until the end of the growing season) and the second factor includes foliar application of paclobutrazol at three levels (0, 50 and 100 ppm) and the third factor including growth-promoting bacteria at five levels (control, Mycobacterium, Azotobacter and Azospirillium and combination). According to the results of analysis of variance, the main effects on chlorophyll fluorescence parameters, flag leaf relative moisture content, flag leaf chlorophyll content and Rubisco activity were significant. According to the results of comparing the mean in the first level of irrigation regime, there was no significant difference between paclobutrazol levels, but in the second level of irrigation regime, the highest percentage of relative leaf moisture was obtained at a concentration of 100 ppm paclobutrazol (66.23%), so that two levels Control and 50 ppm were in a lower statistical group (52.95 and 56.63%, respectively), but in the third level of irrigation regime, the highest trait was obtained at a concentration of 100 ppm paclobutrazol with 55.36% and The lowest was evident at the control level with 38.24%. The interaction effect of irrigation regime on paclobutrazol on Rubisco activity was significant so that in the first level of irrigation regime there was no significant difference between levels of paclobutrazol, but in the second and third levels of irrigation regime the highest amount of rubisco was 100 ppm paclobutrazol. They belonged to 37.63 and 29.27 units, respectively, and the lowest amount of trait was in the control factor.