Effect of drought stress and some Bio fertilizers (Pseudomonas fluorescens, Azotobactore chroococcum and mycorrhiza) on growth, photosynthetic pigments and some physiochemical traits of Calendula officinalis

The use of plant interconnectedness with mycorrhizal fungi and growth promoting bacteria is one of the ways to reduce drought stress that has recently been used in agriculture. A factorial experiment based on a completely randomized design with four replications was designed and conducted in winter and spring of 1396-1396 in research greenhouse of the Faculty of Agriculture, Ferdowsi University of Mashhad. Experimental treatments consisted of 2 levels of drought stress (100 and 50% Field Capacity) and 8 levels of bio fertilizer (Pseudomonas fluorescens (Ps), Azotobactore chroococcum (Az), mycorrhiza fungi (M), Ps + M, Az + M, Ps + Az, Az + Ps + M and control (no bacteria and fungi). The results showed that drought stress (50%FC) in Calendula led to decrease in plant growth, leaf area, flower number, flower diameter, shoot and root dry weight, petal Dry weight and stomata conduction significantly compared to control treatment (100% FC), and also the amount of proline, total carbohydrate and chlorophyll content of the plant increased in drought stress. Application of growth stimulating bacteria in most traits led to improved traits measured in plant under stress and non-stress conditions. The highest leaf area was obtained by application of Azotobactore chroococcum (286.88 mm 2). The highest flower dry weight was in Pseudomonas fluorescence treatment (4.22 g) under 100% FC and after that without significant difference, in treatment of combination mycorrhizal fungus and Pseudomonas fluorescence at 100% FC (3.18 g) was recorded. As a result, the application of Pseudomonas fluorescence in soil alone or in combination with mycorrhizal fungi under drought stress conditions has the ability to improve plant growth and led to increased plant efficiency under drought stress conditions.