Hypocotyl growth of Pinus pinaster seedlings. Changes in osmotic potential and cell wall composition

The changes in osmotic potential and cell wall composition of hypocotyl cell walls from different hypocotyl regions were investigated during growth of etiolated seedlings of Pinus pinaster Aiton. The osmotic potential in the subapical 5 mm part was minimum when hypocotyl growth rate was low, and increased when the fast growth phase began. The main non-cellulosic sugars of the cell wall from pine hypocotyl were arabinose, galactose, xylose, glucose and uronic acids, although their relative proportions were different from those found for angiosperm cell walls. Non-cellulosic glucose was the sugar showing the most important changes during hypocotyl growth as well as along the hypocotyl, suggesting that a glucose-rich polysaccharide is involved in a very active turnover during growth. A partial degradation of a xyloglucan during growth is suggested.