Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA.
Forestry Department, Bulolo University College, Bulolo, Morobe Province, Papua New Guinea.
New Phytol. 2012 Jan;193(1):229-240. doi: 10.1111/j.1469-8137.2011.03917.x. Epub 2011 Oct 13.
• The lack of extant lianescent vessel-less seed plants supports a hypothesis that liana evolution requires large-diameter xylem conduits. Here, we demonstrate an unusual example of a lianoid vessel-less angiosperm, Tasmannia cordata (Winteraceae), from New Guinea. • Wood mechanical, hydraulic and structural measurements were used to determine how T. cordata climbs and to test for ecophysiological shifts related to liana evolution vs 13 free-standing congeners. • The tracheid-based wood of T. cordata furnished low hydraulic capacity compared with that of vessel-bearing lianas. In comparison with most nonclimbing relatives, T. cordata possessed lower photosynthetic rates and leaf and stem hydraulic capacities. However, T. cordata exhibited a two- to five-fold greater wood elastic modulus than its relatives. • Tasmannia cordata provides an unusual example of angiosperm liana evolution uncoupled from xylem conduit gigantism, as well as high plasticity and cell type diversity in vascular development. Because T. cordata lacks vessels, our results suggest that a key limitation for a vessel-less liana is that strong and low hydraulically conductive wood is required to meet the mechanical demands of lianescence.
• 缺乏现存的无导管木质藤本植物支持这样一种假说，即藤本植物的进化需要大直径的木质部导管。在这里，我们展示了一个来自新几内亚的不寻常的无导管木质藤本被子植物例子，即 Tasmannia cordata（木通科）。 • 我们利用木材力学、水力和结构测量来确定 T. cordata 如何攀爬，并测试与藤本植物进化相关的生态生理变化，与 13 种自由生长的近缘种进行比较。 • 与具有导管的藤本植物相比，Tasmannia cordata 的基于管胞的木材提供的水力容量较低。与大多数非攀爬的亲缘植物相比，T. cordata 的光合速率、叶片和茎的水力容量较低。然而，T. cordata 的木材弹性模量比其亲缘植物高 2 到 5 倍。 • Tasmannia cordata 为被子植物藤本植物的进化提供了一个不寻常的例子，它与木质部导管巨型化无关，同时在血管发育方面表现出较高的可塑性和细胞类型多样性。由于 T. cordata 缺乏导管，我们的结果表明，对于无导管的藤本植物来说，一个关键的限制因素是需要具有高强度和低水力传导性的木材，以满足藤本植物的机械需求。
