Kalmar “orthotropous” sifa ce da ake amfani da ita wajen siffanta tsarin halittar kwayar halittar kwai a cikin tsirrai, ma’ana ita madaidaiciya ce kuma tana da axis. Kalmar botanical ce da aka samo daga kalmomin Helenanci "orthos," ma'ana madaidaiciya, da "tropos," ma'ana juya. Ana yawan amfani da wannan kalmar a cikin nazarin ilimin halittar shuka da ilimin halittar haihuwa.
