ONLINE IMAGE COLLECTION

About the Image

Reproductive stem of Monotropsis odorata (sweet pine sap; Ericaceae), a nonphotosynthetic plant endemic to the southeastern United States. As a myco-heterotroph, M. odorata obtains carbon resources from associated mycorrhizal fungi and has a highly reduced vegetative morphology consisting of an underground root mass that produces one to many diminutive reproductive stems (3.5–6 cm in height). Upon emerging from the soil in the late fall, reproductive stems and immature buds are light lavender in color and covered by fleshy bracts and sepals. However, over the course of the subsequent winter months, bracts and sepals become scarious, drying to a light brown. Reproductive stems, encased in dried bracts and sepals, mature early the following spring and upon anthesis, flowers become fragrant (like baking cloves) and are pollinated by Bombus spp. Fruit set ensues over the subsequent 8–10 weeks, with pungently fragrant fruits attracting animals for seed dispersal.

Monotropsis odorata is notoriously difficult to locate in the wild, likely owing to the dried bracts and sepals that cover reproductive stems and flowers, rendering them inconspicuous against the ambient pine and oak leaf litter among which they grow. Manipulations of reproductive stems have shown that these cryptic vegetative bracts conceal more conspicuously colored floral and stem tissues and significantly reduce floral herbivory, leading to higher fruit set, a component of plant reproductive fitness. This finding offers strong support to a growing body of literature documenting the ecological dynamics of plant defensive coloration.

For further detail, see: Klooster et al.—Cryptic bracts facilitate herbivore avoidance in the myco-heterotrophic plant Monotropsis odorata Volume 96, Issue 12, pages 2197–2205. Photo credit: Matthew R. Klooster.