López-Climent M F, Arbona V, Pérez-Clemente R M, Zandalinas S I, Gómez-Cadenas A
Departamento de Ciencias Agrarias y del Medio Natural, Universitat Jaume I, Castelló, Spain.
Plant Biol (Stuttg). 2014 Jan;16(1):79-87. doi: 10.1111/plb.12006. Epub 2013 Apr 10.
Industry residues, phosphate fertilisers and wastewater as a source of irrigation have considerably increased levels of heavy metals in the soil, mainly cadmium (Cd(2+)). To test the effects of a calcium (Ca(2+)) treatment on Cd(2+) accumulation and plant tolerance to this heavy metal, plants of two citrus genotypes, Cleopatra mandarin (CM) and Carrizo citrange (CC), were watered with increasing concentrations of Cd(2+), and phytochelatin (PC) and glutathione (GSH) content were measured. Both genotypes were able to synthesise PCs in response to heavy metal intoxication, although CM seems to be a better Cd(2+) excluder than CC. However, data indicate that CC plants had a higher capacity for regenerating GSH than CM plants. In this context, the effects of Ca(2+) treatment on Cd(2+) accumulation, plant survival and PC, GSH and oxidised glutathione (GSSG) content were assessed. Data indicate that treatment with Ca(2+) had two positive effects on citrus physiology: it reduced Cd(+2) uptake into roots and also increased GSH content (even in the absence of Cd(2+)). Overall, the data indicate that although Cd(2+) exclusion is a powerful mechanism to avoid heavy metal build-up into photosynthetic organs, the capacity to maintain optimum GSH levels to feed PC biosynthesis could also be an important factor in stress tolerance.
工业废渣、磷肥以及废水作为灌溉水源，已大幅提高了土壤中的重金属含量，主要是镉（Cd(2+)）。为了测试钙（Ca(2+)）处理对Cd(2+)积累以及植物对这种重金属耐受性的影响，用浓度递增的Cd(2+)浇灌两种柑橘基因型的植株，即埃及蜜橘（CM）和卡里佐枳橙（CC），并测定了植物螯合肽（PC）和谷胱甘肽（GSH）的含量。两种基因型植株在重金属中毒时均能合成PC，不过CM似乎比CC更能有效排除Cd(2+)。然而，数据表明CC植株再生GSH的能力比CM植株更强。在此背景下，评估了Ca(2+)处理对Cd(2+)积累、植株存活以及PC、GSH和氧化型谷胱甘肽（GSSG）含量的影响。数据表明，Ca(2+)处理对柑橘生理有两个积极作用：它减少了根系对Cd(+2)的吸收，还增加了GSH含量（即使在没有Cd(2+)的情况下）。总体而言，数据表明，虽然排除Cd(2+)是避免重金属在光合器官中积累的有力机制，但维持最佳GSH水平以支持PC生物合成的能力也可能是胁迫耐受性的一个重要因素。
