DISTRIBUTION OF NITROGENOUS AND CARBOHYDRATE FRACTIONS AND OTHER SUBSTANCES IN EXPOSED AND COVERED PINEAPPLE SISTER SHOOTS

Abstract

40 pairs of sister shoots, 1 pair per mother plant, were subjected to different intervals of light vs. darkness experimentation. 1 of the shoots from each pair being covered with an oilcloth bag, the other left exposed. At 17, 56, 77 and 105-day intervals 5-10 plants were harvested, weighed and their moisture, dry matter, and electrical resistance detd. They were analyzed for chlorophyll, titratable acidity, pH, Ca, reducing sugars and sucrose and for different nitrogenous fractions. Water content, electrical resistance, and titratable acidity were higher and dry-matter values and pH lower in the covered than in exposed plants. Organic acid formation in the chlorophyllous sections of the exposed plants appeared to be associated with photosynthetic processes since it was favored by light and inhibited by darkness. In the non-chlorophyllous tissues of the stem and leaves formation of organic acids was of a respiratory type. The chlorophyll content was greater in the exposed than in the covered plants. In the old leaves of the covered plants chlorophyll broke down; in the new leaves it failed to develop. Nitrate N moved more readily into and was assimilated at a greater rate by the exposed than the covered plants. Organic N was considerably greater in the exposed than in the covered plants. There was little or no difference in the reducing sugar content of the exposed and covered plants. However, the sucrose content of exposed plants was considerably greater than that of covered plants, indicating that storage substances did not accumulate in the absence of light. Ca, moving with the transpiration stream, was more abundant in the tissues of the exposed than of the covered plants.