褪黑素对镉胁迫下紫苏根系特征的影响

为揭示根系在褪黑素缓解植物镉胁迫效应中的作用,利用水培实验探讨了外源褪黑素对不同浓度镉处理(0、2、10 mg·kg^-1)下紫苏(Perilla frutescens)生长、根系形态及解剖结构、镉及相关必需元素含量等的影响。结果显示:镉处理显著抑制了紫苏地上部生长,未造成紫苏根系生物量显著改变,但根系形态和解剖结构发生显著变化,长度变短、直径变粗、表面积减小、中柱变粗、皮层占横切面的比例降低;低浓度镉处理的紫苏在添加外源褪黑素后,地上部生物量显著提高,根系镉含量和累积量、镉转运系数以及地上部镉含量和累积量显著下降,同时根系长度变长、中柱变细、皮层占比增加,根系中锌和铁的含量显著增加;高浓度镉处理的紫苏在添加外源褪黑素后,镉转运系数和地上部累积量显著降低,根系中锌含量显著增加,但地上部生物量没有增加。研究表明,外源褪黑素可以通过改变紫苏根系形态和解剖结构,同时增加锌和铁元素吸收,降低根系对镉的吸收以及向地上部位的转运,进而缓解镉胁迫对紫苏生长的抑制作用,但缓解作用因紫苏受镉胁迫程度不同而有所差异。

Effects of exogenous melatonin on root characteristics of Perilla frutescens under cadmium stress

To reveal the role of melatonin-induced root trait variation in alleviating plant cadmium stress, this study recorded the variation in growth, cadmium, and other metal elements contents, as well as morphological and anatomical traits of Perilla frutescens roots under different levels of cadmium stress and exogenous melatonin treatments using hydroponic experiments. The results showed that cadmium stress significantly reduced the growth rate of P. frutescens. Root biomass did not respond to cadmium stress, but root morphological and anatomical traits were significantly affected by cadmium stress. Cadmium stress resulted in shorter roots, thicker root diameter, reduced root surface area, thicker stele, and a reduction in the proportion of cortex in cross-section. Under exogenous melatonin application with low cadmium stress, the above-ground biomass was significantly increased, and root cadmium accumulation and concentration, translocation, and the content and accumulation of cadmium in above-ground parts were significantly decreased. Concurrently, the root length increased, the stele was thinner, the proportion of cortex in the cross-section increased, and the contents of zinc and iron in roots increased significantly. The application of melatonin under high cadmium stress resulted in decreased cadmium translocation and accumulation in aboveground parts and increased zinc content in roots. However, aboveground biomass did not increase. The results indicate that exogenous melatonin can reduce the absorption and translocation of cadmium in P. frutescens and reduce cadmium stress by changing root morphological and anatomical traits, as well as by increasing the absorption of zinc and iron. However, the mitigation effects are affected by the degree of cadmium stress.