Physiological Investigations on the Banana Plant: With seven Figures In the Text

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Abstract
A quantitative study has been made of the way in which the nitrogenous compounds which are present in the banana fruit are affected by the changes that ensue subsequent to harvest. This was done with special reference to Musa acuminate cv. Gros Michel as grown in Central America (Part A), but comparative data are furnished for the cultivars and for material from other areas of cultivation (Part B). In the cultivar Gros Michel from Honduras, the amides (asparagine and glutamine) and histidine play a predominant role in the soluble nitrogen fraction of the fruit. Prominent changes occur in the nitrogen (N) compounds as the fruit ripens, and these are shown to be markedly influenced by the conditions that obtain during the development of the fruit. The nitrogenous composition of the fruit (Gros Michel) is markedly affected by the season of the year at which it forms (Part C); this affects the balance between the amides (asparagines and glutamine) and histidine, and also influences the post-harvest metabolic behaviour in ways which are described. While the total protein of the fruit is relatively stable in its amino-acid composition, certain differences are noted which seem to characterize the cv. Gros Michel as it grows in Central America, and some shifts in the amino-acid balance in the protein do seem to occur with ripening. A typical growth curve for the parthenocarpic fruit of M. acuminate cv. Gros Michel is given, and the changes in the N compounds that occur during development (Part D) are related to this and to the seasonal effects referred to in Part C. The very young inflorescence is first relatively rich in soluble N compounds. After the early phase of growth (cell division) has elapsed, the fruit utilizes its soluble N in synthesis faster than it is supplied to the fruit, so the soluble N complement falls to a low level; thereafter it increases again to a new higher level at harvest. The composition of the soluble N fraction as stored at harvest is quite different from that which obtains in the inflorescence in which the fruit is being initiated. The latter emphasizes the amides (asparagine and glutamine) and hi8tidine; the former emphasizes alanine and glutamine as the only prominent amide. The trend of events is markedly affected by the time of year when the fruit develops—development in the winter leading to a low amide (especially glutamine)/ high histidine condition; whereas development in the summer leads to a high amide (asparagine and glutamine) /low histidine condition at the normal time of harvest. In the more rapid development of summer-grown fruit, certain changes in N compounds occur after harvest, which in the slower developing winter-grown fruit precede the harvest. The different regions of the fleshy fruit, i.e. the fleshy pericarp (endocarp) and the inner region composed of carpels, differ greatly in the total quantity and in the composition of the nitrogenous compounds they contain. The carpels are richer in soluble N and contain all of the amide of the ripe fruit.

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