The development of phloem anastomoses between vascular bundles and their role in xylem regeneration after wounding in Cucurbita and Dahlia
The development of phloem anastomoses between vascular bundles and their role in xylem regeneration after wounding in Cucurbita and Dahlia
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DOI：
10.1007/bf00262647
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发表时间：
1996-04-01
期刊：
影响因子：
4.3
通讯作者：
Barnett, JR
中科院分区：
文献类型：
--
作者：
Aloni, R;Barnett, JR
已在 Cucurbita maxima Duchesne、C. pepo L. 和 Dahlia pinnata Cav 的茎节间研究了连接纵向维管束的韧皮部吻合的分化。这些吻合包含天然存在的再生筛管，其从年轻节间的束间薄壁细胞重新分化。在所有三个物种中，切断幼嫩节间的维管束会导致木质部再生，从而在伤口周围立即形成弯曲的旁路。这些年轻节间的大量韧皮部吻合不参与该过程，再生血管仅源自束间薄壁组织。相反，在大丽花成熟节间，再生血管起源于束间形成层的起始部分，其韧皮部吻合不影响木质发生的模式。另一方面，在南瓜的老节间，束间形成层尚未发育，束间的薄壁细胞失去了再分化为导管成分的能力，而是在韧皮部吻合处产生了再生导管。因此，血管束的受伤区域并没有通过最短的弯曲路径绕过，而是通过距离伤口更远的更迂回的路径。韧皮部吻合中产生的一些再生血管非常宽，可能是有效的水导体。有人提出，韧皮部吻合的致密网络在进化过程中发展起来，作为适应成熟节间可能损伤的机制，通过为具有有限或没有束间形成层的植物的有效木质部再生提供灵活的替代途径。
The differentiation of phloem anastomoses linking the longitudinal vascular bundles has been studied in stem internodes of Cucurbita maxima Duchesne, C. pepo L. and Dahlia pinnata Cav. These anastomoses comprise naturally occurring regenerative sieve tubes which redifferentiate from interfascicular parenchyma cells in the young internodes. In all three species, severing a vascular bundle in a young internode resulted in regeneration of xylem to form a curved by-pass immediately around the wound. The numerous phloem anastomoses in these young internodes were not involved in this process, the regenerated vessels originating from interfascicular parenchyma alone. Conversely, in mature internodes of Dahlia, the regenerated vessels originated from initials of the interfascicular cambia, and their phloem anastomoses did not influence the pattern of xylogenesis. On the other hand, in old internodes of Cucurbita, in which an interfascicular cambium was not yet developed, the parenchyma cells between the bundles had lost the ability to redifferentiate into vessel elements, and instead, regenerated vessels were produced in the phloem anastomoses. Thus, the wounded region of the vascular bundle was not bypassed via the shortest, curved pathway, but by more circuitous routes further away from the wound. Some of the regenerated vessels produced in the phloem anastomoses were extremely wide, and presumably efficient conductors of water. It is proposed that the dense network of phloem anastomoses developed during evolution as a mechanism of adaptation to possible damage in mature internodes by providing flexible alternative pathways for efficient xylem regeneration in plants with limited or no interfascicular cambium.