Roles of gibberellins in increasing sink demand in Japanese pear fruit during rapid fruit growth

Abstract

Our previous work demonstrated that exogenous gibberellins (GAs) applications during rapid fruit growth significantly increases sink demand and results in a larger fruit in Japanese pear. In an attempt to unravel the mechanism of increased sink demand by applied GAs, the histology, cell wall components of the flesh, and carbon accumulation in the fruit were assessed for Japanese pear (Pyrus pyrifolia, cultivar 'Kousui'), as were the activities of sucrose-and sorbitol-cleaving enzymes. Our results show that most vascular tissues occurred in core tissue with very little vascular tissue in the flesh. Application of a mixture of GA 3 + GA 4 in lanolin paste significantly increased the amount of ethanolinsoluble solids, e.g., total pectins, hemicellulose, and cellulose in the cell walls. There was a significantly increased sink demand (assessed by 13 C accumulation in the fruit) by the applied GAs, and this increased sink strength was closely related to increased activities of cell wall-bound invertase in the core, neutral invertase and NAD-dependent sorbitol dehydrogenase in the flesh during rapid fruit growth. As well, concentrations of sorbitol and sucrose in the flesh were decreased by GA application, while glucose concentration increased. Most importantly, the fact that sink activity can be increased by GA application implies that endogenous GAs are likely to be important modulators for sugar metabolism. Hence, selecting for genotypes with elevated GA production in the growing fruit and increased activities of key enzymes for sugar metabolism could result in increased fruit size.

Hormonal regulation of fruit set, parthenogenesis induction and fruit expansion in Japanese pear

“…These results suggest that endogenous GAs are causally involved in fruit set and growth of pear. Although the changes of bioactive GAs contents in pear fruit have been investigated (Zhang et al 2007a) and the roles of GA 3+4 in increasing sink demand during rapid fruit growth has been partly elucidated (Zhang et al 2005c(Zhang et al , 2007b, there is no information their individual roles native GAs in each of fruit set and fruit growth. Auxin can also be an important factor in fruit set and development, and auxin application has often been successful in improving fruit set in such plants as tomato, citrus, and grape (Pharis and King 1985).…”

Physiological Roles of Polyols in Horticultural Crops

“…This hypothesis is supported by the finding that stem girdling and suppression of S6PDH expression decrease the supply of sorbitol into sink tissues and affect SDH activity (Berüter and Feusi, 1997;Zhou et al, 2006). Roles for gibberellins in increasing sink strength and SDH activity have also been reported in Japanese pear fruit (Zhang et al, 2007).…”

Producción y calidad poscosecha de tomate (Solanum lycopersicum L.) larga vida sometido a la aplicación de ácido giberélico

“…En frutos de pepita, el ácido giberélico es el responsable de la fuerza de vertedero (Zhang et al, 2007), lo cual genera un aumento en la translocación de agua y carbohidratos hacia el fruto. Zhenming et al (2008) determinaron que con 50 mg L -1 de ácido giberélico se aumentó la absorción de K en frutos de uva, esto podría indicar que en tomate una mayor absorción de K en los frutos generaría aumento en la translocación de azúcares que aumentarían el tamaño de los mismos, tal como se evidenció con la aplicación de 10 y 100 mg L -1 de ácido giberélico.…”