Buckwheat (Fagopyrum esculentum) pollen by SEM. Buckwheat is not a cereal grain but is a seed related to rhubarb and sorrel. It does not contain gluten and is a suitable substitute for cereals. Buckwheat's lipid-lowering effects are due in part to its rich supply of flavonoids, particularly rutin. Flavonoids are phytonutrients that protect against disease by extending the action of vitamin C and acting as antioxidants. Enhanced SEM. Image width: 116.4 micrometers. Magnification: 860x if the image is printed 10 cm wide.