Response of some grain maize physiological parameters to drought stress and application of auxin and cytokinin hormones

  Drought is one of the major environmental conditions that adversely affect plant growth and crop yield. In the face of a global scarcity of water resources, water stress has already become a primary factor in limiting maize production worldwide. It’s because Phytohormones such as auxin and cytokinin are reported to be involved in the regulation of plant response to the adverse effect of drought stress conditions. This study carried out in order to evaluate some physiological parameters response to auxin and cytokinin hormone alternation under drought stress condition on maize (cultivar KSC 704). The experiment was carried out in three separately environments included non-drought stress environment (irrigation after soil moisture reached to 75% field capacity), drought stress in vegetative stage (irrigation after soil moisture reached to 50% field capacity in V4 to tasseling stage, but irrigation after soil moisture reached to 75% field capacity in pollination to physiological maturity stage) and drought stress in reproductive stage (irrigation after soil moisture reached to 75% field capacity in V4 to tasseling stage and irrigation after soil moisture reached to 50% field capacity in pollination to physiological maturity stage). cytokinin hormone in three levels (control, spraying in V5 –V6 and V8-V10 stages) and auxin hormone in three levels (control, spraying in silk emergence stage and 15 days after that) was laid out as a factorial design based on randomized complete block with three replications in each environment at Seed and Plant Improvement Institute (SPII), Karaj, Iran, in 2013. It was used Indole-3-butyric acid and N6-benzyladenin as auxin and cytokinin hormones respectively. Concentration of used auxin and cytokinin hormones were 10 and 50 mg per liter respectively. In this study some physiological parameters were measured including leaf area index, cell membrane stability, leaf chlorophyll content, stomata conductive, canopy temperature depression, photosynthesis quantum efficiency and leaf senesce. The maximum leaf area index, stomata conductance and quantum efficiency of photosynthesis and the minimum canopy temperature were obtained with spraying cytokinin hormone in V8-V10 stage, and the maximum chlorophyll content index, quantum efficiency of photosynthesis and the delay in leaf senescence were obtained with spraying auxin hormone in silk emergence stage and the minimum stomata resistance and canopy temperature were obtained with spraying cytokinin hormone in 15 days after silk emergence stage. The interaction effect between drought stress and spraying hormone was significant on leaf area index and canopy temperature depression and spraying hormones on maize in drought stress condition in reproductive stage more effective than non-drought stress and vegetative drought stress conditions because it can be useful in balancing the disturb hormone relations. Based on the result of this experiment, maize is tolerant to drought stress in vegetative stage, as a result, irrigation after soil moisture reached to 50% field capacity in vegetative stage and irrigation after soil moisture reached to 75% field capacity after tasseling stage can save irrigation water without any decrease significantly in physiological parameters at erase where water has been limited. Spraying cytokinin and auxin hormones in V8 –V10 and silk emergence stage can be recommended as the best time to use these hormones respectively. Using auxin and cytokinin hormones under drought stress condition in maize was more effective than control and vegetative stage because they can balance the disturbed hormones rate under that condition.