Effect of pH on Mycorrhizal Formation of Slash Pine in Aseptic Culture
Abstract:Substrate pH strongly influenced mycorrhizal formation and growth of slash pine (Pinus elliottii var. elliottii) seedlings in aseptic culture. Vermiculite substrates changed the pH of unbuffered nutrient solutions from pH 3.0 to pH 6.4-6.7 in less than 48 hours after autoclaving. Sand substrates caused only slight changes. Phosphate and phthalate buffers were either inhibitory or lethal to Cenococcum graniforme, Laccaria laccata, and Suillus luteus grown in agar medium or aseptic sand culture in combination with slash pine seedlings or alone. Small quantities of peat moss mixed with vermiculite adequately offset the buffering action of vermiculite and established stable pH reactions. Mycorrhizal synthesis occurred with each of the three fungi at pH 4.0, 4.6, 5.6, and 6.6 when the peat moss-vermiculite mixtures were used. All mycorrhizae developed best in less acid substrates. Control seedlings lacking mycorrhizae were significantly less vigorous than those with mycorrhizae. C. graniforme, which formed the least mycorrhizae, contributed strongly to seedling growth, especially at pH 4.0 and 4.6. S. luteus also formed few mycorrhizae but contributed significantly to seedling vigor in the acid substrates. L. laccata formed abundant mycorrhizae and enhanced seedling growth at all pH levels.
Document Type: Journal Article
Affiliations: Plant Pathologist, The Forestry Sciences Laboratory, Corvallis, Ore.
Publication date: March 1, 1965
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