A Study On Molecular And Physiological Mechanisms Underlying The Influences Phosphorus On Cadmium Tolerance In Populus Cathayana

Heavy metal pollution is a significant problem,especially in fast growing areas of the industry.Cadmium(Cd),a strong phototoxic heavy metal,is commonly released into the arable soil from industrial processes and farming practices.Fertilizer management can influence Cd concentration on crops.Phosphate fertilizer usually contains Cd in varying concentrations,reflecting the Cd content of the rock from which the fertilizer has been derived.As important economic and green tree species,Populus widely planted in China.In recent years,it has also become important tree species as bioenergy resources.Thus,studies on the growth dynamics,physiological characteristics and stoichiometrics of poplar trees in different phosphorus concentrations under exogenous Cd activity and exploring the optimum ratio of phosphorus to reduce Cd in the environment of important theoretical and practical significance.In this study we plant Populus cathayana Rehd which is endemic to China and is mainly grown in North and Northwest China,Liaoning and Sichuan as raw materials.Two months later,is grown with the following nutritional solutions of different phosphorus ratios.Phosphorus concentrations increased in degrees of 0 mMP(non-P),2 mM P(normal-2P),4 mM P(high-4P)and exogenous Cd(4 week treatment)The tree was harvested.Measure the physiological parameters and analyze the expression of related genes,the main results are as follows:(1)When the concentration of phosphorus is kept constant at 2 mM under the influence of exogenous Cd,the biomass,leaf area,photosynthetic rate,total root surface area reached the maximum value.At the absence of P,the biomass,leaf area and photosynthetic rate were significantly reduced,indicating the role of P in reconciling Cd stress.(2)At 2 mM P concentration,total sugar,protein,ATP and GSH increased,suggesting that the poplar has the best ability to absorb and assimilate phosphorus in this nutrient medium.(3)At the m RNA level,the up-regulated expression of ABCC and PCS indicated that 2 mM P levels could increase the tolerance of cadmium to poplar;the up-regulated expression of PHT1;5,a gene involved in P transport,at 2 mM P level promoted the assimilation of phosphorus and Increased use efficiency of P.(4)Among three different levels of P set in this study the medium P levels(2 mM)are more suitable for the development of P.cathayana plants in medium containing Cd.