The accumulation of heavy metals in soil has serious influence on plant growth and ecosystem balance. It is of great importance to explore the mechanism of plant tolerance to heavy me-tals. Although spinach is supposed to have strong Cu tolerance, the effects of Cu on mineral element absorption and cell ultrastructure are still unclear. In this study, the growth of spinach seedlings, the absorption of mineral elements and the ultrastructure of leaf cells were examined in a pot experiment. The results showed that Cu2+ accumulation in the root of spinach seedling was less than that in the shoot when CuSO4 concentration was 100 mg·L-1, with root growth being increased and shoot growth being slightly decreased. When copper concentration continued to increase, the growth parameters continuously declined. When the CuSO4 concentrations were less than 400 mg·L-1, the foliar N, K, Ca, Mg and Fe concentrations of spinach seedling increased, and that of P decreased. The concentrations of N, P and K in roots went down and that of Ca, Mg and Fe went up. All organelles in leaf cells were clearly visible. The basal granule layer was arranged orderly, and the inner and outer membranes of chloroplasts were intact. When the CuSO4 concentrations exceeded 600 mg·L-1, foliar N concentration increased while that of P, K, Ca, Mg and Fe decreased. The concentrations of N, P, K, Ca, Mg and Fe in roots declined. The cell ultrastructure of spinach seedlings substantially changed with the increases of CuSO4 treated concentrations. The chloroplast in leaf cells became rounder, the chloroplast membrane became thinner, the stroma and basal granule layer became less, and the layer accumulation height decreased. The nucleus was broken up and small black spots were found in vacuoles and cell walls, which might be attributed to the enhancement of intracellular swelling pressure caused by high accumulation of Cu2+. In conclusion, low concentration of CuSO4 had little negative effect on the life activities of spinach seedlings, and the high concentrations of CuSO4 did not terminate their growth, indicating that spinach seedlings had strong copper resistance.
土壤重金属积累严重影响植物生长和生态系统平衡,探寻植物对重金属的耐性机理尤为重要.菠菜可能具有一定的耐铜性,但Cu对其矿质元素吸收、细胞超微结构等方面的耐性机理尚不明确.本研究以菠菜幼苗为研究对象,通过盆栽试验,探究不同浓度铜处理对菠菜幼苗生长、矿质元素吸收、叶片细胞超微结构等指标的影响.结果表明: 100 mg·L-1 CuSO4处理浓度时,菠菜幼苗根Cu2+积累量小于地上部,其根系生长量增加,地上部生长量稍有下降,继续增加铜处理浓度,植物体各器官生长参数均呈下降趋势.低浓度铜处理时(<400 mg·L-1 CuSO4),菠菜幼苗叶N、K、Ca、Mg、Fe含量增加,P含量减少;根N、P、K含量减少,Ca、Mg、Fe含量增加;叶片细胞内各细胞器清晰可见,基粒片层排列仍较为整齐,叶绿体内外膜完整.高浓度铜处理时(>600 mg·L-1 CuSO4),菠菜幼苗叶N含量增加,P、K、Ca、Mg、Fe含量减少;根N、P、K、Ca、Mg、Fe含量均减少;叶片细胞内叶绿体变圆,叶绿体膜变薄,基质、基粒片层变少,层堆积高度下降,细胞核解体,液泡、细胞壁中有黑色小点分布,可能是大量Cu2+聚集导致细胞内膨压增大所致.低浓度铜处理并未对菠菜幼苗的生长生理特性产生明显的负面影响,而高浓度铜处理并未终止菠菜幼苗的生长.说明菠菜幼苗具有一定的耐铜性.
Keywords: cell ultrastructure; copper addition; copper tolerance mechanism; mineral elements transportation; spinach seedling.