Vascular constraints on leaf out and flowering in plants

University Of Minnesota Duluth, Duluth MN

Investigators

Abstract

The timing of major events like flowering and germination mediates how plants respond to their environment, and has implications for population growth, interactions with other organisms, and large scale ecosystem processes. Relatively little is known about whether there are physiological and anatomical constraints on the timing of major events like leaf out in the spring in temperate trees. Without this knowledge, it is challenging to understand the ecological and evolutionary implications of different strategies in timing and to predict how species will respond to environmental change. The primary goal of this project is to examine the relationship between seasonal changes in the water transport system of trees and the timing of the re-distribution of resources in the early spring. This research will highlight the importance of resource mobilization in supporting leaf and flower production and examine whether vascular anatomy and physiology could explain interspecific variation in spring phenology.  A major part of the work will be completed by undergraduates, graduate students and a postdoctoral researcher, who will have the opportunity to learn valuable skills and network with scientists at multiple sites.  Research results will be used to develop laboratory curriculum on plant physiology that directly connects the vascular biology of trees to freezing tolerance. The curriculum will be used during an annual program for high school students held at the University of Minnesota Duluth. New growth relies on resources transported in the vascular system, and therefore environmental conditions that reduce vascular function, including cold temperatures, can limit the development of new tissue. Most species in temperate environments must re-activate or repair their vascular system in the early spring before they can support young leaves and flowers. In general, there are two strategies plants use to restore vascular function: activating previously differentiated cells and/or producing new transport cells from cambial initials. It has been hypothesized that plants that rely on the production of new transport cells (at least in the xylem) cannot support early leaf out. If this is true for both the xylem and phloem, then the mechanism that species use to restore vascular function could determine how early in the growing season plants can produce leaves and flowers. To test this hypothesis, this study will characterize the relationship between plant phenology and the mechanism of vascular re-activation in deciduous, woody species. Because floral hydration does not always require both parts of the vascular system, this research will also examine the mechanism of floral hydration and consider its implications for floral freezing tolerance. This research will increase knowledge of vascular re-activation in the spring, which is a core part of plant physiology in seasonal climates, and help to understand vascular re-activation, a critical but understudied process in the vascular system.