GROWTH OF ANANAS COMOSUS (L.) MERR., AT DIFFERENT LEVELS OF MINERAL NUTRITION UNDER GREENHOUSE AND FIELD CONDITIONS. II. CHEMICAL COMPOSITION OF THE TISSUES AT DIFFERENT GROWTH INTERVALS

This report supplements the earlier report (13) which discussed the growth rates, water and mineral nutrient intake by the same group of plants. The data herein considered deal with the chemical composition of the leaf and stem tissues at different growth intervals of pineapple plants grown in nutrient solutions in the greenhouse and in soil under field conditions with different amounts of nitrate, potassium, and calcium. The plant tissues were analyzed for total nitrogen, soluble organic nitrogen, potassium, calcium, reducing and total sugars; the latter hydrolyzed by invertase. The methods for potassium and calcium were reported in a previous publication (9). Total nitrogen and soluble organic nitrogen were determined by the Kjeldahl procedure, using selenium oxychloride as catalyst in the oxidation of organic matter. The fractionation of total and soluble organic nitrogen was conducted according to technique reported previously (7, 8). Reducing sugars, total sugars, and sucrose, the latter by the difference between total and reducing sugars after hydrolysis with invertase, were determined according to the method of Quisumbing and Thomas (6). Starch was determined by the method of Pucher and Vickery (5).