Wahid A, Khaliq S
Department of Botany, University of Agriculture, Faisalabad, Pakistan.
Plant Biol (Stuttg). 2015 Sep;17(5):1005-12. doi: 10.1111/plb.12326. Epub 2015 Apr 17.
Heavy metals greatly alter plant morphology and architecture, however detailed mechanisms of such changes are not fully explored. Two experiments were conducted to investigate the influence of cadmium (CdCl2 · 2.5H2 O) on some germination, morphological, biochemical and histological characteristics of developing embryonic tissue of maize. In the first experiment, maize seeds were germinated in increasing levels of CdCl2 (200-2000 μm) in sand and measurements were taken of changes in germination and seedling development attributes. Based on these parameters, 1000 μM CdCl2 was chosen for detailed biochemical and histological measurements. In the second experiment, seeds were germinated in Petri dishes and supplied with 0 (control) or 1000 μM CdCl2 (Cd-treated). Radicle, plumule, coleoptile and coleorhiza were measured for biochemical and histological changes. The highest amount of Cd was in the coleorhiza and radicle. Free proline, soluble sugars, anthocyanin, soluble phenolics, ascorbic acid, H2 O2 and MDA were significantly higher in coleorhizae, followed by the coleoptile, radicle and plumule. Although the radicle and coleorhiza were relatively poor targets of Cd than the other tissues, Cd stress reduced cortical cell size and vascular tissues, and deformed xylem and phloem parenchyma in all plant parts. In conclusion, the main reason for reduced germination was the influence of Cd on architecture of the coleorhiza and coleoptile, which was the result of oxidative stress and other physiological changes taking place in these tissues.
重金属会极大地改变植物的形态和结构，然而此类变化的详细机制尚未得到充分探究。我们进行了两项实验，以研究镉（CdCl₂·2.5H₂O）对玉米发育中的胚组织的一些萌发、形态、生化和组织学特征的影响。在第一个实验中，玉米种子在含不同浓度CdCl₂（200 - 2000 μM）的沙子中萌发，并对萌发和幼苗发育属性的变化进行测量。基于这些参数，选择1000 μM CdCl₂用于详细的生化和组织学测量。在第二个实验中，种子在培养皿中萌发，并分别供应0（对照）或1000 μM CdCl₂（镉处理）。对胚根、胚芽、胚芽鞘和胚根鞘进行生化和组织学变化的测量。胚根鞘和胚根中的镉含量最高。胚根鞘中的游离脯氨酸、可溶性糖、花青素、可溶性酚类、抗坏血酸、H₂O₂和丙二醛含量显著更高，其次是胚芽鞘、胚根和胚芽。尽管胚根和胚根鞘相对于其他组织而言是镉的相对较弱靶点，但镉胁迫仍会减小所有植物部位的皮层细胞大小和维管组织，并使木质部和韧皮部薄壁细胞变形。总之，发芽率降低的主要原因是镉对胚根鞘和胚芽鞘结构的影响，这是这些组织中发生氧化应激和其他生理变化的结果。
