© 2003 Heron Publishing—Victoria, Canada
Photosynthate distribution patterns in cherrybark oak seedling sprouts
Brian Roy Lockhart (1, 2, 3), John D. Hodges (4), Emile S. Gardiner (5) and Andrew W. Ezell (6)
1. Louisiana State University, Baton Rouge, LA 70803-6202, USA / 2. USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776,
USA / 3. Author to whom correspondence should be addressed (blockhart@fs.fed.us) / 4. Department of Forestry, Mississippi State University, Mississippi State, MS 39762, USA / 5. USDA Forest Service, Center for Bottomland Hardwoods Research, Stoneville, MS 38776, USA / 6. Department of Forestry, Mississippi State University, Mississippi State, MS 39762, USA / Received October 17, 2002; accepted February 9, 2003; published online October 1, 2003
Summary
We used 14C tracers to determine photosynthate distribution in cherrybark oak (Quercus pagoda Raf.) seedling sprouts following release from competing mid-story vegetation. Fall acquisition of labeled photosynthates
by seedlings followed expected source–sink patterns, with root and basal stem tissues serving as the primary sinks. Four months
after the seedlings had been labeled with 14C, they were clipped to induce sprouting. First-flush stem and leaf tissues of the resulting seedling sprouts were the primary
sinks for labeled photosynthates stored in root tissues. Second-flush stem and leaf tissues, and first-flush stem and leaf
tissues the following growing season, were not primary sinks for labeled photosynthates stored in root tissues despite the
high radioactivity in root tissues. Root tissues appeared to deposit photosynthates in a layering process whereby the last
photosynthates stored in new xylem were the first to be depleted during the initiation of a growth flush the following spring.
There were more labeled photosynthates in roots of released seedling sprouts compared with non-released seedling sprouts,
indicating increased vigor of released seedling sprouts in response to greater light availability. In contrast, stem and source
leaf tissues of non-released seedling sprouts contained greater percentages of labeled photosynthates compared with released
seedling sprouts, indicating either greater sink strength or poorly developed xylem and phloem pathways that created inefficiencies
in distribution to root tissues. The 14C distribution coefficients confirmed the distribution patterns and provided additional information on the important sinks
in released and non-released cherrybark oak seedling sprouts.
Keywords:
14C labeling, carbon allocation, mid-story control, oak reproduction, Quercus pagoda, release.
