Effect Of Root Iron Plaque On Photosynthetic Capacity Of Acacia Auriculiformis Under Acid Stress

Acid mineral soil intensifies the pollution of heavy metal and hinders the implementation of phytoremediation techniques,thus brings great resistance to ecological restoration.Acacia auriculiformis is a fast growing tree which can survive in acid mineral soil and its roots are coated with iron plaque in acid（p H2.5）matrix.This experiment was carried out to investigate whether the iron plaque could improve the acid resistance ability of Acacia auriculiformisand the mechanism of its action.Seedlings were set into two groups of iron film and no iron film and three acidity gradients were set at the same time:p H 2.0,3.0 and 4.5 which were regulated by H₂SO₄.The light response curve and chlorophyll fluorescence parameters were measured after a week,then the content of Malondialdehyde（MDA）and hydrogen peroxide（H₂O₂）as well as the differential expression genes was sampled and analyzed.The results showed that:（1）The iron plaque content in the sand culture group was significantly higher than in water culture,and the iron plaque content reduced with the decrease of p H.（2）With the increase of acid stress intensity,net photosynthetic rate and light saturation point decreased.Under the same acid level,the net photosynthetic rate and light saturation point in the sand culture group were significantly higher than those in the hydroculture group.（3）Acid stress significantly affected the trend of OJIP curves.The fluorescence parameters Fv/Fm of the hydroculture group was less than the sand culture group,indicating that photosystemⅡof the sand culture group was less damaged under acid stress.（4）Light-trapping complex,Calvin cycle and photosynthesis related genes decreased in the hydroculture group,While some of these genes upregulated in the sand culture group.Above all,there are a significant difference in photosynthetic capacity between the sand culture group and the hydroculture group,indicating that the sand culture group covered with iron plaque may have a higher acid resistance.