Armstrong JE; Douglas AW 1989

• Authors: Armstrong JE; Douglas AW
• Title: The ontogenetic basic for corolla aestivation in scrophulariaceae
• Location: Bulletin of the torrey botanical club, 116 (4). 1989. 378-389.
• Abstract: The two corolla aestivation patterns that delimit the subfamilies antirrhinoideae and rhinanthoideae in scrophulariaceae were investigated in 38 genera representing 15 tribes. The ontogenetic events producing the two patterns are reported for Scrophularia atrata (Antirrhinoideae) and Rhinanthus mediterraneus (rhinanthoideae), which are representative of the the entire survey. The corolla primordia of scrophularia and other Antirrhinoideae are initiated simultaneously in a whorl. A subsequent adaxial acceleration of corolla growth along with orientational differences results in the adaxial portion of the corolla folding over the abaxial portions. In Rhinanthus and other rhinanthoideae a corolla primoridum is initiated on the abaxial side of the floral apex followed by a unidirectional initiation of the remaining corollar and androecial primordia toward the adaxial side. The accelerated abaxial growth, along with some orientational differences, results in the abaxial corolla lobes folding over the adaxial lobes. The early developmental stages of corolla formation appear to be systematically conservative, unambiguous characters that lead to characteristic patterns of corolla aestivation. The ontogenetic patterns are interpreted as evidence of independent evolution of zygomorphy in each subfamily.