Methods:
For each study species, branching roots (5-10 cm deep) will be traced from the stem and excised. Fine roots (< 2 mm) will be dyed in methylene blue solution for 8-24 hours and then scanned for later image processing. Images will be analyzed using the IJRhizo extension for the ImageJ program for branching order, branching angles, interbranch distance, and root diameter distribution. Coarse roots will be used to determine xylem vessel length and xylem vessel density using optical microscopy. The xylem vessels will be stained by forcing dye through the segment. Small cross-sections will excised from the segment and fixed on plates for later imaging at our home lab.
Unbranching or sealed root segments of 5-10 mm diameter will be selected from previously excised branches. Root axial hydraulic conductance will be measured by inducing a pressure differential across the segment and monitoring the flow of 0.1M KCl using a pressure differential sensor meter (Omega PX26-005GV). Conductance will be normalized by the branch dimensions to provide the root hydraulic conductivity. The response of conductivity to water stress will be determined by the pressure sleeve and bench dehydration methods. Measurements will be spread across the growing season to coordinate with collaborators who will be conducting research at the site
Funding agency:
UMBS Student Research Funding