Effect of water deficit on the cell wall of the date palm (Phoenix dactylifera 'Deglet nour', Arecales) fruit during development

Abstract

Date palm is an important economical crop in many countries. However, in recent years, the Kebili region with the largest palm groves of Tunisia faced an important deficit of rain fall that can impaired the maturation and quality of the fruits especially in non-irrigated plantation. Water deficit does not stop fruit development but has a dramatic effect on fruit growth, pulp content and the cell wall composition and remodeling during maturation. The data indicate that the cell wall was more hydrophilic suggesting that these subtle changes in the cell wall property may participate in maintaining the water status of the cells and the flexibility of the cell wall under water deficit. Date palm (Phoenix dactylifera) is an important crop providing a valuable nutrition source for people in many countries including the Middle East and North Africa. In recent years, the amount of rain in North Africa and especially in the Tunisian palm grove areas has dropped significantly. We investigated the growth and cell wall remodelling of fruits harvested at three key development stages from trees grown with or without water supply. During development, cell wall solubilization and remodelling was characterized by a decrease of the degree of methylesterification of pectin, an important loss of galactose content and a reduction of the branching of xylan by arabinose in irrigated condition. Water deficit had a profound effect on fruit size, pulp content, cell wall composition and remodelling. Loss of galactose content was not as important, arabinose content was significantly higher in the pectin-enriched extracts from non-irrigated condition, and the levels of methylesterification of pectin and O-acetylation of xyloglucan were lower than in irrigated condition. The lower levels of hydrophobic groups (methylester and O-acetyl) and the less intensive degradation of the hydrophilic galactan, arabinan and arabinogalactan in the cell wall may be implicated in maintaining the hydration status of the cells under water deficit. © 2012 Blackwell Publishing Ltd.