JXB Advance Access originally published online on April 24, 2008
Journal of Experimental Botany 2008 59(8):1997-2007; doi:10.1093/jxb/ern061
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
The peripheral xylem of grapevine (Vitis vinifera) berries. 2. Anatomy and development
1Section of Plant Biology, University of California, Davis, CA 95616, USA
2Department of Viticulture and Enology, University of California, Davis, CA 95616, USA
3Department of Plant Sciences, University of California, Davis, CA 95616, USA
* To whom correspondence should be addressed. E-mail: kashackel{at}ucdavis.edu
It has been hypothesized that the substantial reductions in xylemic water flow occurring at veraison are due to physical disruption (breaking) of the xylem as a result of renewed berry growth. In a companion paper, evidence was presented that the vast majority of xylem tracheary elements remained intact despite the growth of the berry, and it was proposed that existing tracheary elements stretch to accommodate growth and that additional elements may also differentiate after veraison. Measurements of the intergyre distance of tracheary elements in macerated tissue were used to test for stretching, and the numbers of tracheary elements per vascular bundle and of branch points of the peripheral xylem network were analysed to test for continued differentiation from 18 to 120 d after anthesis in Chardonnay berries. The distance between the epidermis and the vasculature increased substantially from pre- to post-veraison, potentially increasing the amount of skin available for analysis of compounds important for winemaking. Tracheary elements continued to differentiate within the existing vascular bundles throughout berry development. Additional vascular bundles also appeared until after veraison, thereby increasing the complexity of the peripheral vascular network. The results also confirmed that tracheary elements stretched by
20%, but this was not as much as that predicted based on the growth of the vascular diameter (40%). These results complete a comprehensive evaluation of grape berry peripheral xylem during its development and show that tracheary development continues further into berry maturation than previously thought.
Key words: Tracheary element, vasculature, vessel, water movement
Received 7 September 2007; Revised 11 December 2007 Accepted 4 February 2008