Influence of Vesicular-Arbuscular Mycorrhizae on Growth, Development, and Nutrient Absorption of Sunflower

Sunflowers are often referred to as hyper-accumulators since they have the ability to uptake excess soil nutrients without causing toxicity to the plant. Vesicular-Arbuscular Mycorrhizae (VAM), a naturally occurring beneficial microorganism found in soil, is known to improve plant uptake of macro and micronutrients through a symbiotic relationship formed between fungi and plant. The objective of this study was to examine the effect of VAM on growth, development, and nutrient absorption of sunflowers.  The study was conducted at the University of Maryland Eastern Shore Agricultural Experiment Station in a complete randomized design with two treatments (Control and VAM) and three replications each.  Three sunflower varieties were used in this experiment; Lemon Queen, Mammoth, and Mexican. Sunflower seeds were sown in small plug trays containing Promix, allowed to germinate in the greenhouse, and seedlings were transplanted in the field.  VAM was applied twice; during sowing of the seeds and at transplanting.  Each variety was harvested at its respective flowering stage.  Plant height, number of flowers, fresh weight of shoots, roots, and flowers, and root length were determined.  Shoots, roots, and flowers were dried, grinded separately, and sent to A&L Eastern Laboratories, Inc. for nutrient analysis. Soil was collected pre- and post-harvest and also sent for nutrient analysis.  VAM had no significant effect on plant height, number of flowers, fresh weight of shoots, roots, and flowers, and root length of Mammoth and Lemon Queen; however, there was significant differences in the number of flowers and root fresh weight in the Mexican variety.  There was no significant difference among treatments in nutrients absorbed in the shoots of all sunflower varieties; however, there were significant differences in the concentration of sulfur and copper in roots of the Mexican plants, and nitrogen and iron concentration and magnesium and boron concentration in flowers of Mammoth and Mexican, respectively.  Mexican sunflowers hyper-accumulated higher amounts of nutrients from soil when compared to the other sunflower varieties.  Further studies are needed to identify sunflower varieties with higher ability to hyper-accumulate undesirable excess of soil nutrients.