Plant Science Division, Research School of Biology, The Australian National University, Canberra ACT 0200, Australia.
Plant Cell Environ. 2012 Jan;35(1):158-68. doi: 10.1111/j.1365-3040.2011.02425.x. Epub 2011 Oct 18.
We determined effects of venation traits on hydraulic conductance of phyllodes (foliage), using an array of Acacia s.str. species with diverse phyllode morphologies as the source of variation. Measurements were made on phyllodes from 44 species, grown in common gardens but originating from different positions along a precipitation gradient. K(phyllode) varied 18-fold and was positively correlated with primary nerve hydraulic conductance, and with primary nerve (vein) density but not with minor nerve density, in contrast with previous studies of true leaves in other dicotyledons. Phyllodes with higher primary nerve density also had greater mass per area (PMA) and larger bundle sheath extensions (BSEs) from their minor nerves. We suggest that higher primary nerve conductivity and density may decrease the distance travelled in the high-resistance extra-xylem pathways of the phyllode. Further, larger BSEs may increase the area available for dispersion of water from the xylem to the extra-xylem tissue. High PMA phyllodes were more common in acacias from areas receiving lower annual precipitation. Maximizing efficient water movement through phyllodes may be more important where rainfall is meagre and infrequent, explaining relationships between nerve patterns and the climates of origin in Australian phyllodinous Acacia.
我们通过使用一系列具有不同叶状形态的金合欢属物种作为变异来源，确定了脉纹特征对叶状结构（叶片）水力传导率的影响。对来自 44 个物种的叶状结构进行了测量，这些物种生长在共同的花园中，但来自降水梯度的不同位置。叶状结构的 K(phyllode) 变化了 18 倍，与初级神经水力传导率以及初级神经（叶脉）密度呈正相关，但与小神经密度无关，这与先前对其他双子叶植物的真叶的研究不同。具有较高初级神经密度的叶状结构还具有更大的比质量（PMA）和从小神经延伸出的更大束鞘扩展（BSE）。我们认为，较高的初级神经传导率和密度可能会缩短在叶状结构高阻力的木质部外途径中的行程。此外，更大的 BSE 可能会增加从木质部到木质部外组织的水分扩散面积。在接受较少年降水量的地区，高 PMA 叶状结构更为常见。在降雨量少且不频繁的地方，最大限度地提高叶状结构中水分的有效移动可能更为重要，这解释了神经模式与澳大利亚叶状金合欢起源地气候之间的关系。
