School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, Australia.
Plant Signal Behav. 2009 Nov;4(11):1091-3. doi: 10.4161/psb.4.11.9798. Epub 2009 Nov 12.
High soil boron (B) concentrations lead to the accumulation of B in leaves, causing the development of necrotic regions in leaf tips and margins, gradually extending back along the leaf. Plants vary considerably in their tolerance to B toxicity, and it was recently discovered that one of the tolerance mechanisms involved extrusion of B from the root. Expression of a gene encoding a root B efflux transporter was shown to be much higher in tolerant cultivars. In our current research we have shown that the same gene is also upregulated in leaves. However, unlike in the root, the increased activity of the B efflux transporter in the leaves cannot reduce the tissue B concentration. Instead, we have shown that in tolerant cultivars, these transporters redistribute B from the intracellular phase where it is toxic, into the apoplast which is much less sensitive to B. These results provide an explanation of why different cultivars with the same leaf B concentrations can show markedly different toxicity symptoms. We have also shown that rain can remove a large proportion of leaf B, leading to significant improvements of growth of both leaves and roots.
高土壤硼（B）浓度导致 B 在叶片中积累，从而导致叶片尖端和边缘出现坏死区域，逐渐沿着叶片向后扩展。植物对 B 毒性的耐受性差异很大，最近发现其中一种耐受性机制涉及将 B 从根部排出。研究表明，编码根 B 外排转运蛋白的基因在耐受性品种中的表达要高得多。在我们目前的研究中，我们已经表明，同一基因在叶片中也被上调。然而，与根部不同的是，叶片中 B 外排转运蛋白活性的增加并不能降低组织中的 B 浓度。相反，我们已经表明，在耐受性品种中，这些转运蛋白将 B 从细胞内毒性区域重新分配到对 B 敏感性较低的质外体中。这些结果解释了为什么具有相同叶片 B 浓度的不同品种会表现出明显不同的毒性症状。我们还表明，雨水可以去除叶片中很大一部分 B，从而显著促进叶片和根系的生长。
