Flower herbivory has a negative impact on plant fitness, but its nature has been less critically studied compared to leaf herbivory.

To understand the effects of flower attributes on herbivory frequency, we investigated the nutrient contents, defense contents, strengths, and herbivory rates on reproductive organs and leaves in Iris gracilipes .

In May 2010 and 2011, we established 2 and 3 plots, respectively, on Mt Aoba, Sendai. For each of all flowers in the plots, we recorded flower opening, initiation of fruit development, fruit maturation, and herbivory rates on reproductive organs and leaves (in 2010, reproductive organs only) on each study day. Moreover, we collected flowers in full bloom and leaves around the plots, and measured nutrient contents, defense contents, and strengths.

Anthers tended to contain rich nutrient contents, whereas ovaries and perianths tended to contain rich defense contents. Leaves, ovaries, and shells of the fruit were harder than pistils, anthers, and perianths. Anthers and petals were more frequently eaten by herbivory than ovaries and leaves.

These results suggest that nutrient-rich organs are susceptible to herbivory, and defense-rich or rigid organs are not susceptible to one. Thus, there is a relationship between chemical composition and property and herbivory, and ovaries is the most protected organ in this species.