Exogenous nitric oxide involved in the accumulation and subcellular distribution of Fe,  Zn and Mn in tomato seedlings under copper stress

A tomato cultivar, Gailiang Maofen 802F1, was selected as the planting material to investigate effects of NO on the absorption and distribution of Fe, Zn and Mn in tomato seedlings under copper stress using nutrient solution cultivation in greenhouse. The results show that the biomass and plant height of tomato seedlings are decreased by 33.7% and 23.1% respectively under the 50 mol/L copper stress, while the addition of 100 mol/L SNP could remarkably alleviate this inhibition effect. For mineral elements, SNP could remarkably increase the Fe and Mn concentrations in roots and stems, and Fe and Zn concentrations in petioles and leaves, and the Zn concentration in stems and the Mn concentrations in petioles and leaves are reduced under the copper stress. Meanwhile the exogenous NO could improve Fe and Zn accumulation amounts in roots, stems, petioles and leaves and Mn accumulation amounts in roots and stems, while the exogenous NO reduces the transformation of the absorbed Fe, Zn and Mn red from roots to shoots. Under the Cu stress, the exogenous NO could remarkably increase the Fe and Zn concentrations in vacuole and organelle of all organs and decrease Fe, Zn and Mn concentrations in cell wall of roots and leaves. Mn mainly concentrates on the cell walls of stems and petioles that function as transport organizations, while its concentrations in vacuole and organelle of petioles and leaves are also increased. These results suggest that the exogenous NO could effectively regulate Fe, Zn and Mn rational distributions in organs and subcellular microzone under the Cu stress, so that the seedlings could keep a better balance between mineral nutrition elements and intracellular ion homeostasis to maintain normal physiological metabolism of tomato.