Reid Rob, Fitzpatrick Kate
School of Earth and Environmental Sciences, University of Adelaide, Adelaide 5005, Australia.
Plant Physiol. 2009 Sep;151(1):413-20. doi: 10.1104/pp.109.141069. Epub 2009 Jul 22.
Boron (B) toxicity is common in many areas of the world. Plant tolerance to high B varies widely and has previously been attributed to reduced uptake of B, most commonly as a result of B efflux from roots. In this study, it is shown that the expression of genes encoding B efflux transporters in leaves of wheat (Triticum aestivum) and barley (Hordeum vulgare) is associated with an ability of leaf tissues to withstand higher concentrations of B. In tolerant cultivars, necrosis in leaves occurred at B concentrations more than 2-fold higher than in sensitive cultivars. It is hypothesized that this leaf tolerance is achieved via redistribution of B by efflux transporters from sensitive symplastic compartments into the leaf apoplast. Measurements of B concentrations in leaf protoplasts, and of B released following infiltration of leaves, support this hypothesis. It was also shown that under B-toxic conditions, leaching of B from leaves by rain had a strong positive effect on growth of both roots and shoots. Measurements of rates of guttation and the concentration of B in guttation droplets indicated that the impact of guttation on the alleviation of B toxicity would be small.
硼（B）毒害在世界许多地区都很常见。植物对高硼的耐受性差异很大，以前认为这是由于硼吸收减少所致，最常见的原因是硼从根部外流。本研究表明，小麦（Triticum aestivum）和大麦（Hordeum vulgare）叶片中编码硼外流转运蛋白的基因表达与叶片组织耐受更高硼浓度的能力有关。在耐性品种中，叶片坏死时的硼浓度比敏感品种高出两倍多。据推测，这种叶片耐受性是通过外流转运蛋白将硼从敏感的共质体区室重新分配到叶片质外体中来实现的。对叶片原生质体中硼浓度以及叶片浸润后释放的硼的测量结果支持了这一假设。研究还表明，在硼毒害条件下，雨水对叶片中硼的淋洗对根和地上部的生长都有很强的促进作用。对吐水速率和吐水滴中硼浓度的测量表明，吐水对缓解硼毒害的影响较小。
