© 2005 Heron Publishing—Victoria, Canada
Aluminum fractions in root tips of slash pine and loblolly pine families differing in Al resistance
Jaroslaw Nowak (1, 2) and Alexander L. Friend (3)
1. School of Forest Resources and Conservation and North Florida Research and Education Center, Institute of Food and Agricultural
Sciences (IFAS), University of Florida, 155 Research Road, Quincy, FL 32351-5677, USA / 2. Corresponding author (jnowak@ufl.edu) / 3. North Central Research Station, USDA Forest Service, 410 MacInnes Drive, Houghton, MI 49931-1134, USA / Received June 17, 2004; accepted August 22, 2004; published online December 1, 2004
Summary
Aluminum (Al) distribution among several cellular fractions was investigated in root tips of seedlings of one Al-resistant
and one Al-sensitive family of slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) grown in nutrient solution containing 100 μM AlCl3 (pH 4) for 167 h. Aluminum present in 5-mm-long root tips was fractionated into cell-wall-labile (desorbed in 0.5 mM citric
acid), cell-wall-bound (retained after filtering disrupted cells through 20-μm mesh) and symplasmic (filtrate following cell
disruption) fractions. When averaged across both species, 12% of Al absorbed by root tips appeared in the symplasmic fraction
and 88% in the apoplasmic fraction (55% as cell-wall-labile, and 33% as cell-wall-bound). On a fresh mass basis, total Al
in root tips was lower in loblolly pine than in slash pine, lower in the Al-resistant slash pine family than in the Al-sensitive
slash pine family, and lower in the Al-resistant families than in the Al-sensitive families across species. Although the data
support the hypothesis that Al-resistant plants limit Al uptake to root apices, they do not exclude other mechanisms of Al
resistance. Differential Al resistance between the species and between slash pine families may also be associated with the
size of the total non-labile and cell-wall-labile Al fractions, respectively. We were unable to identify the basis for differential
Al resistance in loblolly pine.
Keywords:
aluminum tolerance, aluminum toxicity, cellular Al, genetic variation, Pinus elliottii, Pinus taeda.
