Effects of UV-B radiation on secondary metabolite production, antioxidant activity, photosynthesis and herbivory interactions in Nymphoides humboldtiana (Menyanthaceae)

Ultraviolet B-light (UV-B) can exert indirect effects on plant-herbivore interactions by inducing changes in constitutive and induced chemical defenses, since it modulates physiological aspects of plants. This study evaluated the action of UV-B radiation on photosynthesis and production of secondary metabolites in Nymphoides humboldtiana and the cascade effects on the relationship of this macrophyte with a generalist herbivore, the gastropod mollusk Biomphalaria glabrata. After 13 days of UV-B exposition under laboratory conditions, the floating macrophyte N. humboldtiana responded increasing its photosynthetic potential and the production of flavonoids with a correlated enhance in antioxidant activity. However, these changes observed in its metabolism were not enough to alter their palatability to consumption by B. glabrata verified through laboratory feeding choice experiments. Despite the known deleterious effects of exposure to UV-B on terrestrial plants, we found that N. humboldtiana does have physiological/biochemical mechanisms as a strategy or restorative response to this potencially adverse or impacting agent without changing its relationships with herbivores.

Keywords: Anti-herbivore defense; Antioxidants; Flavonoids; Freshwater environment; Natural products; Photosynthetic efficiency.