PARENT SESSION
Poster Session #72: Water Relations II.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Wood density, xylem conductive efficiency and xylem cavitation resistance in twenty-two species of chaparral shrubs.

Jacobsen, Anna^*,1, Davis, Stephen¹, ¹ Pepperdine University, Malibu, California

ABSTRACT- Dehydration tolerance and minimal seasonal water potential in woody plants have been associated with high resistance of xylem conduits to cavitation. It remains unclear what xylem traits limit resistance to cavitation. Is there a tradeoff between cavitation resistance and water transport efficiency? Alternatively, does increased cavitation resistance require increased carbon allocation to xylem (e. g. greater wood density)? These questions were examined by measuring xylem conductive efficiency (m² MPa ^-1 s ^-1 ), mean vessel diameter (m), and water potential at 50% cavitation relative to wood density (kg m ^-3 ) in twenty-two chaparral species in the Santa Monica Mountains of southern California. Wood density was found to be poorly associated with xylem conductive efficiency (r² = 0.23) and mean vessel diameter (r² = 0.09). In contrast, wood density was strongly associated with water potential at 50% cavitation (r² = 0.61). This suggests that there is a correlation between the wood density of chaparral and its high resistance to xylem cavitation and that wood density may represent a cost of cavitation resistance.

KEY WORDS: chaparral, wood density, xylem cavitation