Poster: Root Biology

Abs # 520: An evaluation of aluminum tolerance in loblolly pine

Presenter:	Moyer, Kari A, kari_moyer@ncsu.edu
Authors	Moyer, Kari A (A)   Silva, Ivo R (B)   Johannes, Eva  (A)   Allen, Nina S (A)   Goldfarb, Barry  (A)   Rufty, Thomas W (A)
Affiliations:	(A): North Carolina State University (B): Universidade Federal de Vicosa, Brazil

A study was initiated to evaluate Al tolerance in pine. Preliminary results and evidence in the literature have suggested that pine is extremely Al tolerant. Experiments were conducted in a hydroponics system with pH and temperature control. Soybean was included to allow comparison with an Al sensitive species. Plants were grown in complete nutrient solution maintained at pH 4.3 +/- 0.2 and exposed to Al⁺³ concentrations ranging from 0-2000 mM. Soybean root growth was inhibited 50% at 15 mM, while growth of pine roots was stimulated above controls at concentrations up to 100 mM and inhibition did not occur until Al⁺³ exceeded 400 mM. ICP analysis revealed that pine and soybean had similar amounts of Al (0.75 mg/gDW) in tissues at the root tip at 15 mM Al⁺³, but lumogallion staining showed that the Al in pine was sequestered in cells and intercellular areas at the root periphery. Plasmolysis treatments and tissue sections were used to investigate Al binding at the cellular plasma membrane-cell wall interface. Staining with lumogallion and with calcofluor white indicated that the great majority of the Al was binding to the plasma membrane in both soybean and pine. With increasing Al⁺³ concentrations, little additional Al accumulated in pine root tissue up to 400 mM Al⁺³ _ext, indicating effective Al exclusion from the root tip.