sorghum -- 002

sorghum -- 002

close-up aphids on sorghum

The flavonoids are not present in the phloem — vascular tissue in plants that conducts the sugars aphids seek — but are in the epidermal cells that form the outermost layer of defense. When aphids repeatedly probe and puncture the epidermal cells with their stylets, or beaks, they take up the flavonoids that lead to their demise.

IMAGE: USDA