Effects of Potassium on Chlorophyll, Acidity, Ascorbic Acid, and Carbohydrates of Ananas Comosus (l.) Merr.

A study concerned with the effects of iron on chlorophyll, acidity, ascorbic acid, and carbohydrate fractions of Ananas comosus was reported in a previous publication (35). Also, the effects of different amounts of potassium on growth and ash constituents of the same plants were reported in a former paper of this series (36). This study is concerned with the effects of potassium on chlorophyll, acidity, ascorbic acid, and different carbohydrate fractions of the same plants. The literature pertaining to the effects of potassium on chlorophyll emphasizes the fact that potassium deficiency may cause chlorophyll breakdown with the subsequent development of brown spots and leaf necrosis comparable to those observed in A. comosus. WAu.L (46) has recognized in tomatoes two types of potassium deficiency symptoms: the first stage marked by a stunted, hard, yellow plant was associated with a high carbohydrate content; and the second, in which the carbohydrate content had greatly diminished, the plant began to grow, turned green, became soft, and at the same time the lower leaves commenced to die progressively up the stem. RIcHARDs and TEMPLEMAN (31) claim that symptoms of potassium deficiency in barley may either be a light yellow color of leaves associated with succulence and rapid death of the leaves or a dark green associated with white or brown spots on the leaves. According to ROHDE (32), leaves of plants adequately supplied with potassium are yellowish green, while those deficient in potassium are deep green and contain more chlorophyll. No yellow color was observed in the leaves of A. comosus supplied with the low amounts of potassium indicated in this study, but instead a deep green color with a few brown spots and leaf tip necrosis was extensive in old leaves. Our information pertaining to the effects of potassium on ascorbic acid is meager. However, ascorbic acid and total carboxylic acid reserves were closely associated with the chlorophyllose tissues of the plant (35, 37, 39). Comparable relationships between ascorbic acid and chlorophyllose tissues were shown by GIROUD (6, 7, 8) for other plants. Ascorbic acid, according to GUHA and GHOSH (11), is synthesized in Phaseolus mungo from mannose by an enzyme at pH 5.8 but not at 7.4. Ascorbic acid in the fruit of A. sativus, a synonym of A. comosus (L.) Merr., described as a reducing factor first by SZENT-GYtRGYI (42), was reported to occur in fair concentrations 1 Published with the approval of the Acting Director as Technical Paper no. 161 of the Pineapple Research Institute, University of Hawaii.