Developmental and Structural Section
Guo, Jinyan , Wilson, Carol .
Packing strategies and meristematic activity in flower buds contribute to the development of novel floral structures in Iris.
Iris is a petaloid monocot with two outer whorls of three parts and three carpels, a pattern similar to most monocots. Unlike most monocots, Iris has differentiated sepals and petals, a petaloid style branch, an inferior ovary and only three stamens. In Iris flowers, the three stamens are opposite to the three sepals and carpels. Novel floral structures contribute to angiosperm floral diversity and in Iris there is a novel structure called the sepal crest. While sepals are typically flattened floral organs in angiosperm, in some Iris species there are linear outgrowths adaxially that make the sepal three-dimensional. In this study, we sampled species representing four types of sepals with these novel structures as well as a species with a typical flattened sepal to determine factors that contribute to the morphological variations of the sepal. Using the light microscope and transverse sections for two or three developmental stages of flower buds we compared the packing strategies of each sepal type and the development of these novel floral structures in relationship with other floral whorls. Our study showed that the coordinated development of sepals, petals, stamens and petaloid style branches gave rise to space for the development of sepal outgrowths. Factors contributing to the space for the outgrowths of a ridge or a crest involved the lost of three stamens, inferior ovary, the displacement of anther thecae and a reduced petal compared to a typical monocot flower. The development of novel structures on the first floral whorl involved the coordination of all four whorls as well as meristematic activity from the adaxial surface of the sepal. The implications of this finding on angiosperm floral diversity are discussed.
Log in to add this item to your schedule
1 - Rancho Santa Ana Botanic Garden/Claremont Graduate University, Botany, 1500 North College Ave., Claremont, CA, 91711, USA
2 - Rancho Santa Ana Botanic Garden, 1500 North College Avenue, Claremont, CA, 91711-3157, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union D/Hyatt
Date: Tuesday, July 10th, 2012
Time: 11:45 AM