Changes in Chemical Composition and Biological Activity of Developing Tung Fruit with Reference to Oil Synthesis.

In a previous study (26) of changes in chemical composition of tung fruit from June 28 through November 29, 1940, it was shown that oil, sucrose, and protein accumulated in tung kernels and that starch and reducing sugar disappeared towards the end of this period. Appreciable quantities of nitrogen and carbohydrates disappeared from the hull as the fruits approached maturity and probably were in part translocated to the kernel to contribute to the substances stored there. However, the reserves lost from the hull accounted for only a small part of those stored in the kernel; hence the oil, sucrose and protein must have been largely synthesized from substances translocated to the kernels from the leaves or from storage tissues of the tree. In the investigation to be described in this paper as in the study previously reported (26), periodic analyses were made of developing fruits to determine the amounts of accumulated oil, and changes in dry matter, carbohydrates and nitrogenous constituents. In addition data were collected concerning: (a) the mineral, pectic acid and tannin contents of the fruit, (b) the characteristics of the oil, (c) the photosynthetic activity of the leaves on bearing shoots, (d) the catalase and respiratory activity of the fruit. The oil present, in mature tung kernels is composed largely of the glyceride of alpha-elaeostearic acid (20) in which the fatty acid radicals contain a conjugate system of double bonds, not found in most vegetable oils. As pointed out previously (26), the reducing sugar and starch are the main sources of carbon for this oil. It has been noted by other investigators (11, 15, 17, 18, 23, 27) that fats and oils are formed from carbohydrates but no satisfactory account is available of the exact mechanism of transformation of carbohydrates into oil (10). A knowledge of the biological activity and changes in composition of the different parts of the tung fruit during development is desirable because it provides fundamental information concerninig the synthesis of oil in tung and because it may ultimately lead to a better understanding of the effects of orchard practices on formation of the oil. Materials and methods SAMPLES OF FRUIT.-In order to eliminate the wide variations in fruits due to genetic differences among seedlingv trees, the study was conducted through1Respectively, Associate chemist (resigned), Agent (resigned), Principal horticulturist, and Soil technologist, Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, United States Department of Agriculture.