Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

D. K. Salunkhe


D. K. Salunkhe


W. S. Boyle


H. H. Wiebe


F. R. Stermitz


R. L. Hurst


D. R. Walker


The ripening of fruit, aside from its economic consequence, is of importance in the study of the development and physiology of plants. The fruit, being the reproductive organ of the plant, is fundamentally necessary for the continuation of the species. The production of fruit is also of major economic importance.

The fruit is nurtured, not only by its own ability when young to produce carbohydrates by photosynthesis, but also by the translocation of sugar and other compounds produced int eh leaves. While young, the fruit appears to function as the modified leaf that it is believed to be. It is when the fruit matures that the changes known as ripening occur. In the ripening of the fleshy fruits, a change in color is usually observed. This change in color is through a loss of chlorophyll and an increase in the color pigments, anthocyanins, carotenes, and/or xanthophylls, etc. As the fruit ripens, an abscission layer is formed between the plant and the fruit; and the fruit eventually falls from the plant. Control of the length of time required for a fruit to develop and mature is attributed largely to genetic characters.

The relation of the ripening fruit to a senescent leaf is apparent in that both lose their chlorophyll and in some cases become colored with other pigments. The eventual fall of leaves is also associated with the formation of an abcission layer between the leaf and the plant body. It seems logical, therefore, that the ripening of fruit could be considered as a senescence process.

To the economic botanist, the control of senescence is of fundamental importance in the preservation of plant products. Control of the fruit could be useful in extending their period of utilization.

In the studies reported here, attempts have been made to investigate the ripening process of the tomato fruit (Lycopersicum esculentum Mill. var. V. R. Moscow). These studies have been oriented toward the induction of ripening and some of the chemical changes that occur thereafter. Attempts have been made to find new agents for the induction of ripening and to examine established ripening inductants such as ethylene gas. This study also reports the effects of magnetic flux on the ripening of a fleshy fruit. This is a new and controversial concept in research on senescence. The effect of light and several light frequencies on the ripening of a tomato fruit has also been investigated. The changes in the concentrations of sugars, acids, and other compounds during the ripening period of tomato fruit ripened by artificial methods are compared with fruit naturally ripened on the plant.



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