Osmotic Pressure and pH Measurements on Cell Sap of Pinus ponderosa

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Abstract
Osmotic pressure measurements made by means of freezing point depressions, and pH values determined electrometrically were made on 1st, 3rd, and 5th yr. needles of P. ponde-rosa. There is a high pH and low osmotic pressure during the period of growth, and a lower pH and higher osm6tic pressure during the dormant period. The pH and osmotic pressure of the cell sap increase with the age of the needles for any given time. The fluctuation of osmotic pressures and pH values becomes less as the age of the needles increases. The needles fell when the pH was approximately 4.1.