Expansion during early apple fruit development induced by auxin and N-(2-chloro-4-pyridyl)-N′-phenylurea: Effect on cell wall hemicellulose

Expansion in apple fruit (Malus domestica Borkh. cv. Braeburn) during early development was induced by injecting 2,4-dichlorophenoxyacetic acid (2,4-D) through the calyx of the fruit and by dipping the apples in N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU). Cell wall composition was analysed, focusing on the hemicellulose fraction containing xyloglucan, a polysaccharide believed to play an important role in cell expansion. Changes were observed in the yields of the cell wall fractions of the fruit treated with either 2,4-D or CPPU, although the monosaccharide composition of the fractions exhibited few differences. There was no decrease in the molecular weight of the xyloglucan from treated fruit. These results are discussed in terms of current cell wall expansion mechanisms.