RELATION OF WESTERN YELLOW PINE SEEDLINGS TO THE REACTION OF THE CULTURE SOLUTION

Abstract

Seedlings of Pinus ponderosa, selected from germinated seeds, were grown in culture solutions ranging in pH value from 2.7 to 11.0. Eleven sets of 35 seedlings were used, each having a different pH value but all having the same nutrients. The limits of growth were at pH 2.7 and 11.0 with maximum growth occurring in the slightly acid solutions. Tops of plants grown in alkaline solutions were stunted and chlorotic and the roots were brown and thickened, with a tendency to disintegrate. The plants were grown for 133 days, then harvested, frozen, thawed, and the sap expressed. The sap was distinctly acid in all cases, but that from the roots had less buffer action than that from the tops. The reaction of the culture solutions was changed by the plants, particularly of those solutions on the alkaline side. No explanation for this action is given.