99th ESA Annual Meeting (August 10 -- 15, 2014)

SYMP 23

Allocation, Stress Tolerance and Transport: How Does Phloem Physiology Impact Plant Ecology?

Carbon fixed by plants serves as the basis of most life in terrestrial habitats, but many questions remain about how plants invest carbon during their lifetime. In vascular plants, carbon is transported from photosynthetic tissue (source) to areas of active growth and metabolism (sinks) in the phloem. Because carbon transport depends on a gradient established by both source and sink activity, it integrates changes that occur throughout the plant, potentially influencing everything from growth and allocation to defense and reproduction. Although the phloem’s role in mediating these processes has intrigued ecologists for decades, proving a direct connection between phloem physiology and plant ecology remains challenging. In this timely symposium, we will bridge the divide between physiologists that are dedicated to unraveling the mechanism of carbon transport, and ecologists who are questioning how carbon movement in plants could influence ecological processes. By integrating a diverse group of scientists, we will synthesize what is known about phloem physiology, carbon allocation and stress tolerance. Our goal is to generate discussion with the larger community about how to fill in gaps that exist between our understanding of phloem function and our knowledge of plant ecophysiology, particularly in light of recent advances in phloem physiology. The organization of the symposium follows the flow of carbon transport from source to sink, highlighting the ecological importance of each part of the pathway. The opening speaker will discuss the ecological implications of different phloem loading mechanisms. Afterwards we will move into the transport pathway with one talk about modeling phloem transport and a second talk about phloem malfunction, specifically whether or not drought-induced mortality is tied to loss of turgor in the phloem. The last three talks will focus on carbon sinks, a topic that will be introduced with a discussion of how source and sink dynamics influence plant growth and allocation. Then we will delve into the biology of two important sinks, chemical defenses and reproductive structures. In these talks, the speakers will highlight how competing sinks impact the induction of defense metabolites and the importance of phloem transport in providing both carbon and water to developing fruits and flowers.