Influence of water stress and assimilation area on the sugar content and organic acid during the growth period in the pear fruits (Pyrus communis L.)cv. 'Williams'

Influence of the early and late water stress and the assimilation area on t he sugar content (glucose, fructose and sucrose), sorbitol and organic acid s (malic, citric, fumaric and shikimic) and the related changes during the growth period in the pear fruits of cv. 'Williams' was studied in 1997. Sug ar and organic acid contents were determined by HPLC analysis. The experime nt encompassed four observations: early water stress (from June 1 till July 15), late water stress (from July 15 till August 17), the 30 per cent defo liation (July 22) and control. Water stress and defoliation had no impact e ither on the diameter, length or weight of fruits, but did influence the su gar and organic acid contents. Late water stress did effect the soluble sol ids, whereas defoliation had negative effect on the soluble solids content. Early water stress caused the decrease of glucose, fructose, sucrose and s orbitol if compared with control. Glucose content rapidly decreased after d efoliation, but oscillated up and down with late water stress, however, it was still lower than that of control.