Departamento de Genética, Escola Superior de Agricultura "Luiz de Queiroz"/Universidade de São Paulo (Esalq/USP), 13418-900, Piracicaba, SP, Brazil.
Departamento de Produção Vegetal, Escola Superior de Agricultura "Luiz de Queiroz"/Universidade de São Paulo (Esalq/USP), 13418-900, Piracicaba, SP, Brazil.
J Environ Manage. 2019 Jun 15;240:84-92. doi: 10.1016/j.jenvman.2019.03.026. Epub 2019 Mar 28.
Distinct tomato genotypes possess different tolerance degree to cadmium (Cd), but the mechanisms behind this phenomenon are scarcely understood. To this end, the physiological, biochemical, anatomical, nutritional and molecular mechanisms associated to the plant tolerance against Cd toxicity were investigated in five tomato accessions with contrasting sensitivity to Cd exposure. Firstly, the data revealed that larger biomass loss was not always coupled to higher Cd concentration, indicating that other events, in addition to the internal Cd accumulation, impact tomato performance at early stages of Cd exposure. Secondly, the results indicated that the fine regulation of nutrient status, particularly magnesium (Mg), boron (B) and manganese (Mn), is associated to the mitigation of Cd toxicity. Magnesium status was coupled to the modulation of root development, resulting in changes in root hair formation and biomass allocation. Boron accumulation in leaves was linked to Cd toxicity, suggesting that tolerance mechanisms involved strategies to decrease or even avoid B excess in photosynthetic tissues. Disturbances in Mn status, i.e. Mn excess in leaves and Mn deficiency in roots, were also related to tomato sensitivity to Cd exposure. Thirdly, plant capacity to maintain leaf blade expansion is a relevant strategy for a better tomato development after short-term Cd exposure. Fourthly, tomato tolerance to Cd-induced stress does not depend on CAT activity enhancements in such conditions. In conclusion, tomato ability to quickly manage its nutritional status is necessary for alleviation of the Cd effects at early stages of exposure to this metal. The better understanding about tolerance mechanisms and mode of action of Cd toxicity in plants can help in the establishment of strategies to mitigate its impacts on crops.
不同的番茄基因型对镉（Cd）具有不同的耐受程度，但对此现象的机制知之甚少。为此，本研究在对 Cd 暴露敏感性不同的五个番茄品种中，研究了与植物耐受 Cd 毒性相关的生理、生化、解剖、营养和分子机制。首先，研究数据表明，较大的生物量损失并不总是与较高的 Cd 浓度相关，这表明除了内部 Cd 积累之外，其他事件也会影响番茄在 Cd 暴露早期的表现。其次，结果表明，营养状况的精细调节，特别是镁（Mg）、硼（B）和锰（Mn），与减轻 Cd 毒性有关。Mg 状况与根系发育的调节有关，导致根毛形成和生物量分配的变化。叶片中硼的积累与 Cd 毒性有关，表明耐受机制涉及减少甚至避免光合组织中硼过量的策略。Mn 状况的紊乱，即叶片中 Mn 过量和根系中 Mn 缺乏，也与番茄对 Cd 暴露的敏感性有关。第三，叶片扩展能力的维持是番茄在短期 Cd 暴露后更好发育的相关策略。第四，在这种条件下，CAT 活性的增强并不是番茄耐受 Cd 诱导胁迫的原因。总之，番茄在早期暴露于 Cd 时快速管理其营养状况的能力对于减轻 Cd 影响是必要的。更好地了解植物对 Cd 毒性的耐受机制和作用模式有助于制定减轻其对作物影响的策略。
