| Research Abstract |
1.Polyuronide and starch content in the flesh of 'La France' pear fruit were measured during 3 years. In all years, polyuronide and starch concentration was kept high during the period 107-139 days after full bloom (DAFB) and then decreased rapidly till about 165 DAFB (the commercial harvest date of 'La' France), though the absolute level was varying with rear. When fruit was harvested at the commercial harvest based on DAFB,softenibg during the subsequent ripening differed with harvest years. From these results, concentrations and compositions of starch and plyuronide in flesh at 110-120 DAFB could be an useful index for predicting softening of fruit after harvest.
2.Incorporation of 14-C photoassimilates into insoluble solid of flesh was observed in 107 and 119 DAFB during the experimantal period in this sudy (107-177 DAFB). This results shows that vigorous sinthesis of polymers in flesh decreased in maturing period.
3.Pear fruits include stone cells in the flesh. Distribution of stone
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cells in pear fruits was observed by staining with phloroglucinol reagent. Most of the stone cells was detected ouitside of the core.
4.Major component of stone cell is liglin, which is the most abundant natural aromatic organic polymers found in all vascular plants, and composed of phenolic substances such as coniferyl, p-coumaryl and sinapyl alcohols in varying ratios in different plant species. For the analysis of lignin content sulfuric acid extraction and determination method with hydroxylamine were tested.
5.For the extraction of phenolic substances in pear flesh, concentraion of several kinds of acids, alkalis and organic solvent were tested, and acetylbromide, chloric acid, sulfuric acid, and perchloric acid were comparetively effective reagents to dissolve phenolic substances.
6.In young pear fruit, contents of acetyl bromide, perchloric acid and sodium hydroxide soluble phenolic substances were greater and those decreased with fruit growth, while sulfuric andChloric acid soluble ones were increased with fruit growth.
7.Results obtained in this study indicates that phenolic substances in flesh cell wall may change during fruits growth and maturation, and/or several kind of phenolic compounds were includes in flesh cell wall. Less
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