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Organic Acid Metabolism and Accumulation During Pineapple Fruit Growth and Development

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Title:Organic Acid Metabolism and Accumulation During Pineapple Fruit Growth and Development
Authors:Saradhuldhat, Parson
Date Issued:2005
Abstract:Pineapple fruit quality is mainly determined by the balance of acid to sugar content. The acidity of ‘Smooth Cayenne’ fruit changes significantly during the few weeks before harvest. To investigate fruit acid accumulation and metabolism, fruit from clone 36-21 a high acid clone and clone 63-555 (DIO) a low acid clone were compared during the 11 weeks of fruit growth and development before harvest. The developmental changes in fruit acidity and sugar content were different between the high and low acid clones. Fruit acidity in the low acid clone increased comparatively earlier, peaked and sharply declined just prior to harvest. In contrast, the high acid clone gradually increased in acidity, peaked at a week before harvest and then declined slightly. At harvest, the high acid clone had higher fruit acidity than the low acid clone. Developmental changes in fruit acidity resulted from changes in fruit citric acid concentration due to a high relationship between citric acid concentration and fruit acidity. The fruit malic acid concentration varied only slightly before harvest in both clones.
Developmental changes in the activities of acid related enzymes citrate synthase (CS), aconitase (AGO), phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH) and malic enzyme (ME) were determined during fruit growth and development. CS activity greatly increased a week before harvest and the increase was coincident with the peak in the citric acid content of the high acid clone. Increased AGO activity was coincident with a sharp reduction in organic acid in the low acid fruit just before harvest. The activities of PEPC, MDH and ME did not directly relate to the changes in fruit acidity. The changes in fruit potassium were significantly correlated with the changes in fruit acidity in both clones during fruit growth and development, although the potassium concentrations were similar between clones at harvest.
It was suggested that the acid accumulation in pineapple fruit during fruit growth and development was mainly due to changes in citric acid concentration. The activities of CS and AGO and the fruit potassium content participated in the regulation of pineapple fruit acid metabolism and accumulation.
Appears in Collections: Ph.D. - Horticulture

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