Chatelet David S, Rost Thomas L, Matthews Mark A, Shackel Kenneth A
Section of Plant Biology, University of California, Davis, CA 95616, USA.
J Exp Bot. 2008;59(8):1997-2007. doi: 10.1093/jxb/ern061. Epub 2008 Apr 24.
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 approximately 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.
据推测，在转色期木质部水流大幅减少是由于浆果重新生长导致木质部物理性破坏（断裂）。在一篇相关论文中，有证据表明，尽管浆果在生长，但绝大多数木质部管状分子仍保持完整，并且有人提出，现有的管状分子会伸展以适应生长，并且在转色期后可能也会有额外的分子分化。通过测量浸渍组织中管状分子的螺距来测试伸展情况，并分析每个维管束中管状分子的数量以及外围木质部网络的分支点数量，以检测霞多丽浆果在开花后18至120天内是否持续分化。从转色前到转色后，表皮与维管系统之间的距离大幅增加，这可能增加了可用于分析对酿酒重要化合物的果皮量。在整个浆果发育过程中，现有维管束内的管状分子持续分化。额外的维管束也一直出现直至转色期之后，从而增加了外围维管网络的复杂性。结果还证实，管状分子伸展了约20%，但这并没有基于维管直径生长所预测的那么多（40%）。这些结果完成了对葡萄浆果发育过程中外围木质部的全面评估，并表明管状分子的发育在浆果成熟阶段持续的时间比之前认为的更长。
