Ether-Soluble Organic Acids of Mature Valencia Orange Leaves

Abstract

IntroductionIn a series of studies (16, 18, 20) on the organic acids of citrus fruits, the authors have pointed out that large amounts of organic acids exist in the juice of the pulp, as compared with exceptionally low concentrations in the peel. The vascular system of the fruit is confined chiefly to the mesocarp (albedo), and the latter thus serves the important function of transporting water and solutes from the tree to the juice vesicles of the pulp. Since these vesicles contain relatively large amounts of organic acids, it would appear that higher concentrations than are present should occur in the mes6carp, that is, if the total organic acid radical is transferred from leaves to vesicles. This situation led to the postulation that the organic acids of the juice are possibly synthesized in the pulp vesicles rather than in the leaves and subsequently transferred to the pulp. Quantitative determination and identification of the organic acids present in the leaves should provide fundamental data necessary for a solution to this problem.The present investigation has been concerned with the extraction of the organic acids from ground, dried Valencia orange leaves with absolute ethyl ether, and with the subsequent determination of total and individual organic acids in the water solution of the ether extract. In addition, water-soluble organic acids were extracted directly from aliquot portions of the dried leaf samples, and these data were compared with the total and individual acids extracted with ether. This information revealed the amounts of organic acids present in the leaves in soluble and insoluble states. The influence of these factors on the buffer system of the leaves is discussed. Furthermore, certain relationships are proposed concerning the synthesis and translocation of organic acids from the leaves to the fruit.

Effects of calcium, potassium, & magnesium on oxalic, malic, & citric acid content of valencia orange leaf tissue

“…Approximately twice as much malic as citric acid, however, is found in citrus foliage and oxalic acid as insoluble Ca-oxalate occurs in even greater concentrations than malic acid in citrus foliage (10).…”

Calcium Concentration and Distribution in Healthy and Decline Peach Tree Tissues1

“…Therefore, based on Chandler's evidence (2), these crystals of Ca-oxalate account for most of the Ca found in peach leaves (Table 1). No report on the presence of Ca in this precipitated form in peach tissues could be found in the literature, although the presence of Ca-oxalate has been reported in tissues of apple (14), elm (7), citrus (12), and tobacco plants (1). There is also strong evidence linking oxalic acid metabolism to Ca-oxalate formation (1,3,6).…”

Oxalate contents of Thai rice paddy herbs (L. aromatica and L. geoffrayi) are affected by drying method and changes after cooking

“…The insoluble oxalates are highly correlated with the insoluble calcium. If this form of calcium is to be utilized by the plant, an enzymatic mechanism or some other process would have to change the insoluble calcium oxalates to other soluble compounds [24]. Oxalates are known to interfere with calcium absorption by forming insoluble salts with calcium [1].…”