CAREER: Linking phloem anatomy and physiology with whole plant changes in resource allocation

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Every year many trees produce new leaves in the spring, lose leaves in the fall, and produce flowers and fruit. These changes involve the movement of resources into and out of organs through the plant vascular system, often at a rapid pace over a short period of time. Despite the importance of these changes to horticulture, agriculture and forest regeneration, relatively little is known about what happens in the vascular system during these time periods. This project uses two new methods for studying carbon transport and vascular anatomy that will address fundamental questions about sugar transport, its stability and how it influences plant growth throughout the plant life cycle. This work is critical to understanding the role of seasonality in determining plant growth and reproduction and will advance the understanding of processes that influence tree growth, crop production, and plant ecology. Being based at a primary undergraduate institution, where research and education are strongly intertwined, this project will train young scientists and mentor students in the laboratory and classroom. Students will help organize a citizen science project focused on plant seasonality and connecting the broader community with science and the local environment. The goal of this project is to better define the role of the phloem in controlling resource allocation. There are three central research aims. (1) Characterize how phloem sap flux and anatomy relate to floral size and habitat affinity. This research will focus on measuring carbon transport and characterizing the relationships between phloem anatomy, floral development and floral size in at least thirty closely related species. (2) Investigate whether phloem transport is coupled with nutrient re-mobilization and pigment production during leaf senescence. This research will examine the relationship between phloem transport velocity, leaf chemistry and nutrient flux in senescing leaves. One part of this project will test whether decreased phloem transport could trigger leaf color change. (3) Determine how phloem anatomy influences seedling allocation and tree growth. This study will investigate whether changes in phloem transport velocity can be predicted during seedling development based on vascular architecture. It will also determine how phloem anatomy scales with height using new immunolocalization protocols developed by the principal investigator.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.