Selection Of Lead And Nickel Enriched Plants And Their Micro-ecological Characteristics In Rhizosphere

The present experiments focus mainly on selection and resources survey of heavy metal enriched plants in Southwest China, especially in Guizhou province. Solution cultures, pot experiments and chemical analysis were used to select the plant species, and then to study their enrichment mechanisms in typical yellow soils widespread in Guizhou province, including the influence of pedology and soil chemistry on the enrichment, and microorganism groups and their bio-characters in rhizosphere. The main object of the studies is to utilize the super heavy metal enrichment plants to rehabilitate the polluted soils and reestablish ecological systems by cultivation of the plants selected. Following are the main results obtained.1. Selection on the lead enriched plants1.1 Five plants species (Agrostis stolonifera, the Lolium perenne, the Cynodon dactylon, the Poa annua and tomato) with Pb tolerance, one plant specie (Asiatic Plantain) with Ni tolerance were selected out from more than 60 species of lawn grasses, crops and weeds collected as seeds and seedlings by micro-plots of field experiments with Pb added. The others died after germination or grew poorly.1.2 The solution culture was adopted to grow the four lawn grasses to realize their tolerance to Pb. Agrostis stolonifera was tallest in height and longest in roots among the four plants, indicating the high tolerance to Pb. In pots, the contents of Pb in plants changed in the sequence: Lolium perenne >Agrostis stolonifera >Poa annua>Cynodon dactylon (according to the highest content in organs). Thus lolium perenne showed strongest ability for Pb absorption which could result from unclear inner mechanisms.1.3 The ratio of Pb contents in upper parts to roots (S/R) could indicate the transportation and distribution of the heavy metal in plants. The transfer abilities of Pb from roots to leaves and stems, determined by the values of S/R, changed in the order: Agrostis stolonifera > Lolium perenne > Cynodon dactylon > Poa annua.1.4 Roots tolerance index (RTI) is the ratio of root lengths under heavy metal stress to those in blank control, well showing the tolerance abilities of the plant to heavy metal stress. According to RTI, The tolerance abilities of plants were: Agrostis stolonifera > Lolium perenne > Poa annua > Cynodon dactylon.