The Effects of the Form of Nitrogen and the Amount of Base Supply on the Organic Acids of Tung Leaves

Abstract

Recent research (10) on the nutrition of the tung plant has demonstrated a close relationship betwen cation uptake and the form of nitrogen supplied. For example, tung seedlings grown with all or part of the nitrogen supplied as the ammonium salt have a lower calcium requirement for optimal growth than do those supplied with only nitrate as the nitrogen source. It has been demonstrated that a close relationship exists in the tung plant between the growth of the tree and the balance of the cations supplied (9). It was the purpose of the present investigation to determine if the form of nitrogen and ratios of cations supplied affect the production of anions within the plant, particularly the organic acids. MethodsOven-dried, midshoot leaves were available from the 1947 experiments on nutrient balance of tung (10). These one year old seedlings had been grown in sand culture in a factorial experiment with three levels of Mg and K (0.5, 2, and 4 millimoles/l.) and three ratios of nitrate N to ammonium N (all NO3; i NO3 to i NH4; i NO3 to i NH4). In a supplementary experiment, the highest levels of K and Mg of the main experiment were supplied with three levels of calcium (0.4, 2, and 5.7 millimoles/l.) in an all nitrate solution, and also in a j NO3 to j NH4 solution. Thus the material represented plants grown under a wide range of cations and of forms of nitrogen supply.Comparable leaves from these trees had been previously analyzed for mineral content, and determinations for total organic acid and oxalic acid content were made essentially as described by PUCHER et al. (7,8), using a Goldfisch extraction apparatus and a Beckman pH meter calibrated at pH 2.6 and 8.0 with appropriate standard buffers. It was found that an organic acid fraction that deteriorated rapidly in alkaline solution was present in the ether extract of tung leaves. This necessitated keeping the extract in ether until within an hour of the time the titrations were made. The ether extract was made alkaline, then the ether was quickly evaporated, the solution cooled, made acid, and the titrations made immediately after adjustment to pH 8.0.The data obtained were calculated as milliequivalents of H per gram of dried leaf, and the difference between the total organic acids by titration and the oxalic acid by permanganate oxidation was calculated as non-oxalic acid fraction. The data for the total and non-oxalic acid fractions are GILBERT ET AL.: ORGANIC ACIDS OF TUNG LEAVESpurely comparative since a proper correction factor (7) was not established for the unknown acids. Oxalic acid was isolated from tung leaves and identified by the formation and melting points of the monohydrate and p-toluidide. The relationships between these three fractions and the treatments supplied the plants were examined in two ways. The organic acid data were tested by analysis of variance for the main effects and interactions of the factorial treatments in the main and supplementary experiments. Multiple regression (11) was used to test for relationships between the organi...

Changes in the concentrations of malic acid, citric acid, calcium and potassium in the leaves during the growth of normal and iron-deficient mustard plants (Sinapis alba)

“…Our results do not contradict this finding, for at no time was there a fall in the amount of calcium per leaf during the period of sampling, so long as the leaves remained green. Gilbert et al (1951), using tung leaves, and Rasmussen & Smith (1961), using Valencia-orange leaves, have shown a correlation between the concentration of calcium and that of oxalic acid.…”

“…Much still remains to be discovered about the relationship between the inorganic and organic constituents, although a few general statements can be made. For example, several workers have found that the content of malic acid or oxalic acid in leaves is related to that of calcium (Gilbert, Shear & Gropp, 1951;Rasmussen & Smith, 1961).…”

Calcium Transport in Apple Trees

“…Ca moved into leaves that were high in metabolic activity. It moved into young leaves and into those sprayed with growth regulators that in- nutrition synthetized less oxalic acid and required less Ca for its neutralization (14). The failure of solutions of salts of these elements to release Ca when passed through stem sections indicates that they do not act through the exchange mechanism.…”

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

“…Several investigations have dealt with the effect of nutrition on organic acids of leaf and fruit tissues (2,3,5,13). In general, the effects of cations on the organic acids in leaf tissue are rather complex.…”

“…For example, Cooil (1) found that the higher total acids associated with high K in expanding guayule leaves was largely accounted for by high citric acid levels, whereas in mature leaves high malic acid levels were associated with high Ca levels. In tung, oxalic acid formation is directly related to nitrate and Ca supply (3).…”