Sweet herbal scents of spring waft through the Lady Bird Johnson Wildflower Center as Elena Leander digs into a research plot, seeking to understand the unsung heroes of Texas’s iconic annual blooms. The 29-year-old ecology graduate student at the University of Texas at Austin wears an earthy green baseball cap and a blue T-shirt that reads “Protect the Underground” as she pounds an eight-inch metal tube into the earth with a sledgehammer to extract a soil sample.Beneath the layers of bluebonnets, yellow Engelmann’s daisies, purple verbenas, and other multicolored delights lies a network of fungi and bacteria that help the plant world extract moisture from the surrounding soil. Leander has spent months probing this patch of southwest Austin to analyze one organism in particular: arbuscular…