BRC-BIO: Understanding tree phloem functioning during drought

点击翻译按钮获取中文摘要

In this time of relatively extreme climate change, it is crucial that we understand how plants interact with the climate, to accurately predict future climate conditions and to inform CO2 mitigation efforts. Currently, forests sequester upwards of 25% of anthropogenic CO2 emissions, annually. However, it is unclear how their ability to sequester CO2 will change in the future, especially in areas that are predicted to have increased droughts. This project will investigate a key unknown underlying our uncertainty around how trees respond to drought: the phloem. The phloem is the “sugar highway” of the plant. It is the pipe that transports sugars that are photosynthesized in leaves to areas that need sugar to grow. If the phloem loses functioning during drought, the resultant lack of an ability to transport sugars to areas in need could reduce photosynthesis or even cause plant mortality. This project will investigate how phloem functions in the context of drought for forest trees. We will use novel Raman spectroscopy methods that allow us to visualize sugar throughout the plant and quantify phloem functioning, among other methods. Additionally, this project will focus on increasing the availability and quality of research experiences for students from under-represented communities through collaborating with students and faculty from the neighboring Holyoke Community College, integrating art into the research process, and providing research opportunities for Smith College students.Droughts are predicted to increase in intensity and frequency around the world. This project seeks to further our understanding of how trees respond to drought by investigating phloem function in whole-plant physiology under drought. The phloem is responsible for transporting sugar from sites of production to sites of need and is driven by positive pressure generated by water. Due to its integral role in whole plant function and its dependence on water, the phloem is hypothesized to be a key regulator of drought responses e.g., photosynthetic down-regulation and mortality. The objectives of this proposal are three-fold: to quantify differences in phloem function during control and drought conditions for mature, forest trees, to understand when the phloem loses function in relationship to photosynthesis, and to investigate how phloem functioning relates to plant mortality. We will approach these objectives through the use of Raman spectroscopy and measuring the rate at which carbon moves in the phloem, alongside other physiological methods. A forest rain-fall manipulation experiment will be established and used in controlled mortality experiments on saplings of northeastern US tree species in controlled environments. This project should improve our understanding of phloem function, and subsequently whole-tree function, in drought conditions.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.