Abstract Detail

Novel Approaches to Plant Evolution from Paleontological, Physiological, and Developmental Perspectives

Roddy, Adam [1].

A physiological approach to the ecology and evolution of flowers.

Flowers are one hallmark of angiosperm evolution. Their appearance among early angiosperms enabled the development of more intimate, coevolutionary relationships with animal pollinators, eventually leading to rapid diversification of both flowers and their pollinators. Although flowers are critical to successful reproduction for most angiosperms, little is known about their physiology. Flowers often encounter similar microenvironments as leaves, yet differences in their functioning imply that leaves and flowers may have divergent physiological strategies. While angiosperm leaves rapidly evolved to increase their water transport capacity because of its positive effect on carbon gain, flowers are mostly heterotrophic and need not transpire large amounts of water. As a result, flowers are predicted to have evolved to reduce their water and carbon costs. Indeed, monocot and eudicot flowers have few, if any, stomata, less leaky epidermises, lower vein densities, and low hydraulic conductances compared to basal angiosperm flowers. Furthermore, the hydraulic structure-function relationships seem to differ among major angiosperm clades, with basal angiosperm flowers having relationships more typical of leaves. Like in leaves, veins in basal angiosperm flowers are positioned to optimally supply transpiration, while lower vein densities in monocot and eudicot flowers likely evolved without a transpiration constraint. These results suggest that early in angiosperm evolution, flower hydraulic architecture transitioned from being optimized for water transport to being optimized for water storage and reduced transpiration. There is, indeed, a tradeoff among flowers between maintaining a high transport capacity and relying on stored water to maintain turgor. Furthermore, contemporary natural selection continues to influence flower physiology and ecology. Analyses of ~60 species from the California flora show that species flowering in hotter, drier conditions are more conservative with reduced rates of water loss. Limiting water loss seems to have been critical to increases in flower size among the monocots and eudicots. Thus, reducing the physiological costs of flowers may have relaxed the strength of non-pollinator selection and allowed other morphological traits to more rapidly track pollinator preference.

1 - Yale University, Forestry & Environmental Studies, 370 Prospect St, New Haven, Connecticut, 06511, United States

Keywords:
water relations
hydraulics
xylem
flower.

Presentation Type: Symposium Presentation
Session: SY11, Novel approaches to plant evolution from paleontological, physiological, and developmental perspectives
Location: 101/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 3:45 PM
Number: SY11006
Abstract ID:94
Candidate for Awards:None