What are the functional consequences of xylem organization?
Fern vascular systems are fundamentally different than most woody plant species, in that they only utilize primary xylem and there is no secondary growth. We’re interested in the functional consequences of xylem organization in ferns and how adaptations in xylem connectivity influence species distributions and drought tolerance. Some species like Bracken Fern (Pteridium aquilinum) have very integrated xylem with many connections, while other species have discrete bundles of xylem that rarely come into contact.
Does xylem organization influence disease and drought tolerance?
Xylem and phloem networks are complex transport systems that deliver water, nutrients, and signals across long distances in plants. They are also the target site and preferred habitat for a variety of xylem- and phloem-dwelling pathogens. The organization of xylem networks can be viewed as a delicate balance between safety and efficiency. Networks with few wide conduits are more efficient at bulk water transport, but aren’t nearly as safe as a network with many narrow, redundant conduits. The number, frequency, and spatial distribution of connections between xylem conduits also plays a major role in how easily water can be redistributed around a blockage in the network (e.g. the xylem networks of leaf tissue highlighted in yellow in the image above). Xylem is a relatively low-resistance pathway through the plant compared to other tissue, an adaptation that facilitates bulk water transport. However, along with water and nutrients, bacteria and air embolisms are also able to travel long distances and between conduits using the same pathways. My research is aimed at better understanding the tradeoffs between safety and efficiency in a wide range of plants, with a special focus on the vascular systems of citrus and how we can optimize those networks to increase productivity and develop tolerance or resistance to bacterial pathogens that live in the xylem or phloem. I use a combination of analytical and visualization tools like high resolution computed X-ray microtomography to study these systems.
