Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species
Article first published online: 29 JUL 2011
© 2011 The Authors. New Phytologist © 2011 New Phytologist Trust
Volume 192, Issue 4, pages 885–897, December 2011
How to Cite
Plavcová, L. and Hacke, U. G. (2011), Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species. New Phytologist, 192: 885–897. doi: 10.1111/j.1469-8137.2011.03842.x
- Issue published online: 11 NOV 2011
- Article first published online: 29 JUL 2011
- Received: 25 May 2011, Accepted: 29 June 2011
- electron microcopy;
- pit membrane;
- ray parenchyma;
- •Intervessel pits act as safety valves that prevent the spread of xylem embolism. Pectin–calcium crosslinks within the pit membrane have been proposed to affect xylem vulnerability to cavitation. However, as the chemical composition of pit membranes is poorly understood, this hypothesis has not been verified.
- •Using electron microscopy, immunolabeling, an antimonate precipitation technique, and ruthenium red staining, we studied the distribution of selected polysaccharides and calcium in the pit membranes of four angiosperm tree species. We tested whether shifts in xylem vulnerability resulting from perfusion of stems with a calcium chelating agent corresponded with the distribution of pectic homogalacturonans (HG) and/or calcium within interconduit pit membranes.
- •No HG were detected in the main part of intervessel pit membranes, but were consistently found in the marginal membrane region known as the annulus. Calcium colocalized with HG in the annulus. In contrast to intervessel pits, the membrane of vessel-ray pits showed a high pectin content.
- •The presence of two distinct chemical domains, the annulus and the actual pit membrane, can have substantial implications for pit membrane functioning. We propose that the annulus could affect the observed shift in xylem vulnerability after calcium removal by allowing increased pit membrane deflection.