Laboratory of Electron and Confocal Microscopy, Faculty of Biology, Adam Mickiewicz University, 89 Umultowska Street, 61-614, Poznań, Poland.
Protoplasma. 2012 Apr;249(2):347-51. doi: 10.1007/s00709-011-0285-2. Epub 2011 May 18.
Plants have developed a range of strategies for resisting environmental stresses. One of the most common is the synthesis and deposition of callose, which functions as a barrier against stress factor penetration. The aim of our study was to examine whether callose forms an efficient barrier against Pb penetration in the roots of Lemna minor L. exposed to this metal. The obtained results showed that Pb induced callose synthesis in L. minor roots, but it was not deposited regularly in all tissues and cells. Callose occurred mainly in the protoderm and in the centre of the root tip (procambial central cylinder). Moreover, continuous callose bands, which could form an efficient barrier for Pb penetration, were formed only in the newly formed and anticlinal cell walls (CWs); while in other CWs, callose formed only small clusters or incomplete bands. Such an arrangement of callose within root CWs inefficiently protected the protoplast from Pb penetration. As a result, Pb was commonly present inside the root cells. In the light of the results, the barrier role of callose against metal ion penetration appears to be less obvious than previously believed. It was indicated that induction of callose synthesis is not enough for a successful blockade of the stress factor penetration. Furthermore, it would appear that the pattern of callose distribution has an important role in this defence strategy.
植物已经发展出了一系列抵御环境压力的策略。其中最常见的策略之一是合成和沉积胼胝质，它作为抵御压力因素渗透的屏障。我们的研究目的是检验在暴露于铅的条件下，是否有胼胝质能有效地阻止铅进入小浮萍（Lemna minor L.）的根部。研究结果表明，铅诱导小浮萍根中胼胝质的合成，但它并没有在所有组织和细胞中被规律地沉积。胼胝质主要出现在根的原表皮和根尖的中心（原形成层中央柱）。此外，只有在新形成的和垂周的细胞壁（CWs）中才形成了连续的胼胝质带，这可以形成一个有效的阻止铅渗透的屏障；而在其他 CWs 中，胼胝质只形成小簇或不完整的带。根 CWs 内胼胝质的这种排列方式不能有效地保护原生质免受铅的渗透。因此，铅通常存在于根细胞内。根据这些结果，胼胝质对金属离子渗透的屏障作用似乎不如之前认为的那么明显。这表明，诱导胼胝质合成对于成功阻止压力因素渗透还不够。此外，胼胝质分布的模式似乎在这种防御策略中起着重要作用。
