Uptake Characteristics And Physiological Response Of Sugarcane To Lead And Cadmium

Lead(Pb) and Cadmium(Cd) are important contaminants in soils and bring great threaten to agriculture and human healthy with the development of industry and agriculture. In order to reduce the environmental problems brought forth by the heavy metal pollution, all kinds of methods have been applied to reduce the harm caused by heavy metals. Phytoremediaton, emerging in recent years as an "green" technology of remediation, has been reported to be a cost-effective, non-intrusive, heavy-metal reusable, aesthetically pleasing and socially accepted technology to remediate polluted soils. One important research field of phytoremediation is using high biomass plants to remediate soils polluted by heavy metal.Pot experiments were conducted to investigate the adsorption characteristics and physiological response of sugarcane to Pb and Cd. The physiological and biochemical indexes in some parts of sugarcanes were studied under single and combined pollution with Pb and Cd progressive stress. We also probed into the difference of sugarcane in uptake, translocation and accumulation of Pb and Cd from soils. At last, Sodium Dodecylbenzene Sulfonate and Tea Saponin were applied to the pot experiments in order to study the effect between Cd content and Surfactantsthe. The purpose of the research is mean to explicit understanding the physiological response of sugarcane to Pb and Cd, offering the theoretics for the tolerance, phytoremediation potential and hygienic safety of sugarcane to Pb and Cd. The results were as following:1. Pb and Cd had different effects on the growth of sugarcane. With the increasing of Pb concentration, the diameter of stems, the burl length of stems and the biomass increased first and decreased afterwards. When the soil Pb added concentration was 250 mg kg^-1, the maximum values of the diameter of stems, the burl length of stems and the biomass were gained. In comparison to the control, they increased by 9.63%, 9.02% and 13.47%, respectively. While the diameter of stems, the burl length of stems and the biomass decreased significantly with the increasing of Cd concentration in the soils.2. Different Pb and Cd concentration in soils had different effects on the physiological properties of sugarcane. In the Pb single pollution experiment, there was a positive correlation between the relative membrane permeability and the Pb concentration with a correlation coefficient 0.999. The content of chlorophyll a, chlorophyll b, and carotenoid of leaves presented significant negative correlations with the Pb concentration in the soil, the correlation coefficient was 0.994, 0.994 and 0.985, respectively. With the increase of Pb concentration, the protein content, the activity of catalase(CAT) of the leaves and the soluble sugar of stems increased first and decreased afterwards, the critical Pb concentration in soil was around 250 mg/kg. In the Cd single pollution experiment, the relative membrane permeability of the leaves increased with the Cd concentration in the soil by S-function and the correlation coefficient was 0.999. The content of chlorophyll a, chlorophyll b, the activity of catalase(CAT) of leaves and the soluble sugar of stems increased with the Cd concentration in the soil by the first order exponential attenuation function. the correlation coefficient was 0.998,0.999,0.971,0.997 and 0.996, respectively.3. In the combined pollution Pb and Cd experiment, different heavy metal in the same concentration produced different effects on the growth of sugarcane in the order: Cd >Pb+Cd>Pb. The order of the total uptake of heavy metal Pb in sugarcane was: single element treatment>Pb+Cd treatment and Cd was: Pb+Cd treatment>single element treatment. The order of the difficulties of Pb and Cd migration in sugarcane-soil systems: Pb+Cd treatment>single element treatment.4. Sugarcane had different capabilities and characteristics of uptake of Pb and Cd. The distribution of Pb was in order: roots>leaves>stems and Cd was: roots> stems > leaves. The transloction factor (TF) values and the bioconcentration factor (BCF) of Pb in every treatment were less than 1 and the capability to transport and adsorb of Pb was poor. The maximal total Pb accumulated in aerial parts of one sugarcane was 3.15 mg. TF values of Cd in every treatment were near or much higher than 1, but BCF values of Cd were less than 1. The maximal total Cd accumulated in aerial parts of one sugarcane is 6.53 mg. The Pb content in sugarcane juice was higher than the prescribed limits of China Food Safety Standard, and thus considered they were not safe to eat.5. Sodium Dodecylbenzene Sulfonate and Tea Saponin could improve the uptake of Cd concentration by sugarcane. In comparison to the control, Tea Saponin can increase the Cd concentration in roots, stems and leaves by 96.91%, 156.80% and 30.08%, respectively.6. The estimated amount of heavy metal accumulated by sugarcane was 429 g/ha for Pb and 889 g/ha for Cd.