| Summary: | 碩士 === 國立中興大學 === 園藝學系所 === 96 === The purpose of this study was to investigate the composition changes in the pulp, peel and cladode of H. undatus at different gowth stages. After onset of peel color change, the concentration of total soluble solids and total soluble sugars in the pulp gradually increased, while starch concentration decreased until the fruit was fully ripened. Mineral nutrition content declined gradually due to dilution effects of fruit growth. Upon ripening, mineral nutrition content in the peel tended to be higher than in the pulp. Despite stable total soluble sugars content throughout fruit growth, starch concentration in the peel declined consistently, implying dehydrated starch might have been transferred to the pulp. Sugars in the pulp, mainly composed of glucose, fructose and a small amount of sucrose, showed the same tendency of variation as the total soluble sugars content. Acid invertase (AI), neutral invertase (NI) and α-amylase are enzymes affecting the accumulation of soluble sugars in pulp. AI, as the key enzyme, was associated with a rapid accumulation of glucose. Malic acid as the predominant organic acid in the peel increased gradually during fruit growth. Titratable acidity of pulp showed a short-lived sugar at the start of color change. Malic acid, also the main organic acid in pulp, showed a similar pattern to its titratable acidity. Other organic acids in pulp were citric acid, ascorbic acid and oxalic acid, but all in small amount. Nutrition levels of cladode remained stable throughout fruit growth.
Spraying lead arsenate caused injury symptoms like brownish and hollowed bruises on the peel surface. The higher the concentration sprayed, the more serious the injury. The titratable acidity, malic and citric acid levels of fruit slightly increased after spraying, while the total soluble sugars, starch, glucose and fructose contents were not affected.
Malate dehydrognase (MDH) activity significantly declined after the spraying, but it gradually recovered and even overtook the control upon maturation of the fruit. Results of mineral analysis showed no increase of arsenic in pulp, therefore the possibility of direct lead arsenate pollution on pulp titratable acidity and organic acid levels had been excluded. Instead, the increment of acidity might be caused by stress injuty of lead arsenate toxicity on the fruit. K and Mg concentrations in pulp were slightly raised after the spraying, while other nutrition elements were not affected.
With fruit bagging treatment, none of the fruit compositions was affected except an increment of L value of peel. Girdling cladode at 16th day after flowering partly promoted fruit maturity and early onset of peel color change. Fruit size, pulp titratable acidity, organic acids, total soluble sugars, fructose and glucose levels significantly decreased mainly due to girdling cladode treatment reduce carbohydrate translocation during this active starch synthesis period in fruit.
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