Floral meristem size and organ number correlation in Eucryphia (Cunoniaceae)
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We present a comparative flower ontogenetic study in five species of the genus Eucryphia with the aim of testing whether differences in the organ number observed can be explained by changes in the meristematic size of floral meristem and floral organs. Species native to Oceania, viz. E. milliganii, E. lucida and E. moorei, have the smallest gynoecia with ca. 6 carpels, while the Chilean E. glutinosa and E. cordifolia present more than ten carpels. E. milliganii has the smallest flower with the lowest stamen number (ca. 50), while the other species produce around 200 stamens and more. Standardized measurements of meristematic sectors were taken in 49 developing flowers that were classified into three well-defined ontogenetic stages. Sizes of meristems varied significantly among species within each developmental stage as revealed by ANOVA analyses. Significant regressions between organ number and corresponding meristem size were consistent with the premise that a larger meristem size prior to organ initiation could be determining for a higher organ number. Flower organogenesis in Eucryphia also involves relevant meristem expansion while the organs are initiated, which results in a particular androecium patterning with a chaotic stamen arrangement. Meristem expansion also appears to be slower but more extensive in species with larger initial meristematic size, suggesting that flower phenotype can be determined in ontogeny by this heterochronic interplay of space and time.
KeywordsFlower development Androecium Polyandry Polycarpellate gynoecium Meristem size Meristem expansion Cunoniaceae
We acknowledge AI for providing the collection and photography of E. moorei. The present work was presented at the JPR International Symposium organized by The Japanese Society of Plant Morphology and Fundación Flores at the 80th Annual Meeting of Botanical Society of Japan in September 2016 in Okinawa. We acknowledge JPR for covering the expenses for attending to this conference. This work has been funded by Fondecyt-Conicyt grant projects 11150847 and 3130417. We acknowledge Royal Botanic Garden Edinburgh (RBGE) for providing suitable material of Eucryphia and Frieda Christie for technical assistance with the SEM. RBGE is supported by the Scottish Government’s Rural and Environmental Science and Analytical Services Division.
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