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Role of mycorrhizal fungi in loblolly pine root tolerance to aluminum.
MacFall, Janet1, 1
ABSTRACT- The response of loblolly pine (Pinus taeda L.) seedlings to exposure of aluminum solutions when planted in sand was studied. Seedlings were aseptically germinated, planted into fine sand, inoculated with Pisolithus tinctorius at 6 weeks following germination, and exposed to aluminum (0 - 1 mM AlCl3, pH 3) solutions for up to an additional 8 weeks. Seedlings were scored for mortality, distress, shoot dry weight and root dry weight. Seedlings were grown in sealed plastic pouches, in sterile sand, in growth changers with filtered air, and watered through a filtered drip irrigation system. For this range of aluminum concentrations, there appeared to be little mortality to aluminum exposure (generally less than 10%). There was no difference in mortality, shoot dry weights or root dry weights between mycorrhizal and non-mycorrhizal seedlings. Nuclear magnetic resonance spectroscopy of the mycorrhizal and non-mycorrhizal roots showed the presence of organic acid ligands in the intact root material. Staining with showed aluminum binding both to plant and fungal cell walls. It was concluded that both mycorrhizal and non-mycorrhizal pines are relatively tolerant of aluminum exposure in solution, and aluminum appeared excluded from the cell interior by cell wall binding.
KEY WORDS: loblolly, aluminum, mycorrhizae