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Enzymic hydrolysis of placental cell wall pectins and cell separation in watermelon ( Citrullus lanatus ) fruits exposed to ethylene
Author(s) -
Elkashif Mohamed E.,
Huber Donald J.
Publication year - 1988
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1988.tb00622.x
Subject(s) - pectinase , citrullus lanatus , pectin , middle lamella , ethylene , cell wall , ripening , chemistry , biochemistry , ultrastructure , botany , enzyme , horticulture , biology , food science , catalysis
Watermelon [ Citrullus lanatus (Thunb.) Matsum and Nakai, cv. Charleston Gray] fruits were examined to determine the effect of ethylene on cell wall hydrolases. pectin degradation, and cell wall ultrastructure. Enzymic studies showed that activity of polygalacturonase (EC 3.2.1.15) increased in placental tissue following 1 day of ethylene treatment and was 10 times higher after 6 days of treatment. The increase in polygalacturonase activity was accompanied by the appearance in ethanol powders of low‐molecular‐weight pectic polymers and a decrease in total pectin. The enhanced enzyme activity and decrease in total pectins were observed only in fruits exposed to ethylene. Ultrastructural studies of ethylene‐treated tissue revealed an early disintegration of the middle lamella. The onset of wall separation coincided with the first notable increase in polygalacturonase activity. Cell wall of untreated fruit showed no evidence of structural changes. The results indicate that initiation of enzymic activity and cell wall separation in response to ethylene are not characteristic phenomena of normal ripening and senescence in watermelon fruit.