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

Abstract

The results obtained at different growth intervals on the chemical composition of the leaves and stems of pineapple plants grown in solution cultures and in the soil with different amounts of nitrate, potassium and calcium were as follows: 1. Total nitrogen in the non-chlorophyllous basal sections of leaves, of meristematic status, and in the stem, correlated positively with the concentrations of nitrate in the nutrient solution, and was greater in the preflowering than postflowering stages of plant growth. In the chlorophyllous distal sections of the leaves, total nitrogen correlated with the nitrate concentrations in the nutrient solutions, but was greater in the postflowering than preflowering growth periods. 2. Potassium in the non-chlorophyllous basal and in the chlorophyllous distal sections of the leaves correlated positively with the concentrations of potassium and negatively with those of calcium in the nutrient solutions. In the non-chlorophyllous basal sections of the leaves and in the stem, potassium concentrations were greater in the preflowering than postflowering stages, but in the chlorophyllous distal sections similar concentrations were reversed. 3. Calcium in the non-chlorophyllous basal and chlorophyllous distal sections of the leaves correlated positively with the concentrations of the same in the nutrient solutions. Calcium concentrations were almost twice as great in the stem as in the leaves, and much greater in the preflowering stage, in the stems, due to the retarded movements of calcium from stem to leaves through the incompletely developed conducting vessels in the meristematic tissues, than in the postflowering stage, with well developed vessels. 4. Sugar concentrations in the non-chlorophyllous basal sections were greater in the low- than high-nitrate cultures. Also, sugar concentrations were lower at the preflowering than postflowering periods. In the chlorophyllous distal sections, sugar concentra!nns were greater in the highnitrate cultures of the series, with variable potassium and constant calcium, they were greater in the low-nitrate cultures. The results indicate that sugars increased in the latter series due to decreased plant growth resulting from the combined effects of low nitrate and potassium concentrations. In the stem, differences in sugar concentrations between different cultures were not as great and distinct as in the leaves, except in the cultures with high concentrations of potassium and nitrate. 5. In field grown plants, sugar concentrations In the nonchlorophyllous basal leaf sections correlated inversely with the nitrate and potassium concentrations of the tissues and with growth. 6. Absolute amounts of sugars or nitrogen perplantincreased with greater plant weights, although the concentration of these substances decreased at rates slightly lower than those of growth, as measured by plant weights. 7. Ratios of sugar concentrations in the chlorophyllous distal sections to the non-chlorophyllous basal sections of the active leaves, indicating potential sugar supplies available to the meristematic tissues of the basal leaf sections for utilization in growth, were greater for the high nitrate cultures and correlated positively with plant growth.