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

Maximum vessel length and vessel continuity in seedlings of white oak and black walnut.

Riley, Joseph^*,1, Pallardy, Stephen¹, ¹ Department of Forestry, Columbia, MO

ABSTRACT- Relatively little is known about the conduit length properties of seedlings despite the importance of the seedling vascular system to water transport. The proclivity for shoot dieback in temperate deciduous angiosperm seedlings suggests that stems may be isolated hydraulically from the rest of the plant during this life stage. We measured maximum vessel lengths (MVL) in seedlings of white oak (Quercus alba L.) and black walnut (Juglans nigra L.) by two techniques: passage of compressed air and infusion of xylem with a 1000:1 suspension of latex paint under a gravity head. Comparisons were obtained for roots and stems as well as for passage of vessels through the root-stem junction portion of the hydraulic transport system. Maximum vessel lengths obtained by the two techniques were similar. Values of MVL were greater for Q. alba (7-13 cm) than for J. nigra seedlings (3-9 cm), and MVLs were somewhat greater in roots (highest MVL = 13 cm) than stems (highest MVL = 9). Vessel continuity across the root-stem junction appeared to be maintained in Q. alba seedlings. In contrast, roots and stems of J. nigra seedlings appeared to be more isolated hydraulically by a lack of vessel continuity across the junction. Vessel lengths exhibited by seedlings of both species were much reduced compared with values reported in the literature for larger plants of congeneric taxa.

KEY WORDS: Quercus alba, Juglans nigra, hydraulic architecture, xylem anatomy