Relationship between Pectic Substances and Calcium in Healthy, Gelated, and Granulated Juice Sacs of Sanbokan (Citrus sulcata hort. ex Takahashi) Fruit

概要

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In order to ascertain the mechanism of hardening of juice sacs during granulation, a physiological disorder of citrus fruit, the stoichiometric relationship between pectic substances and levels of Ca^<2+> in healthy, gelated, and granulated juice sacs from Sanbokan fruit was investigated. Pectic substances in the hot-water fraction had higher concentrations of methoxyl groups and acetyl groups, while those of the EDTA fraction had lower concentrations of these groups. The amount of Ca^<2+> in the hot-water fraction was approximately equivalent to the amount of free carboxyl groups, but that in the EDTA fractions was, in most cases, more than equivalent to the amounts of those groups. The amount of Ca^<2+> per unit amount of pectic substances in the EDTA fraction was higher in gelated and granulated juice sacs than in healthy juice sacs. The possibility is discussed that crystallization of pectic substances, as a result of increased levels of Ca^<2+> in the middle lamella, causes the hardening of the juice sacs.
日本植物生理学会の論文