noun
keel petal
Botanical term for the two fused lower petals in flowers of the Fabaceae (pea) family, forming a keel-like structure.
マメ科の花では、竜骨弁が雄しべと雌しべを包んでいる。
In legume flowers, the keel petal encloses the stamens and pistil.
翼弁 are the two lateral petals (wings) in papilionaceous flowers, distinct from the keel formed by 竜骨弁.
Compound of 竜骨 (keel, literally 'dragon bone') and 弁 (petal), describing the keel-like shape of the fused lower petals.