Effects Of Cadmium Stress On Disease Resistance Of Male And Female Poplars

The elemental defense hypothesis holds that heavy metals have certain biological toxicity to pathogenic bacteria and can enhance plant resistance when they are absorbed by plants and enriched in vivo.Because the tolerance response of different sex plants to heavy metal stress is different,based on the comprehensive element defense hypothesis and the tolerance difference of male and female plants to heavy metal stress,this study proposed the hypothesis that the accumulation of heavy metals in trees can enhance the disease resistance of trees,and the effect of heavy metals on the disease resistance of different sex plants is different.In order to verify this hypothesis,this study investigated the difference of disease resistance between male and female Populus deltoides under Cd stress under soil culture conditions,in order to provide scientific basis for the selection of tree sex for phytoremediation in heavy metal contaminated areas.The results are as follows:（1）Populus deltoides has high tolerance and can accumulate high levels of heavy metals in woody plants.It was found that Populus deltoides was highly tolerant to cadmium and could also accumulate cadmium in high concentration.At the same time,due to its high adaptability and better growth performance,Populus deltoides has been widely planted all over the world.（2）Populus deltoides treated with cadmium at 50 mg·kg^-1concentration showed a better disease resistance and no disease spot was found on its leaves compared to control.After inoculation with Pestalotiopsis,the disease index of Populus deltoides treated with cadmium was significantly lower than that of Populus deltoides untreated with cadmium.At the same time,plants grew well,seedling height and ground diameter did not change significantly.There were no significant changes in chlorophyll and nutrient contents（reducing sugar,total sugar,soluble protein）in leaves of Populus deltoides.Resistance traits such as polyphenols,tannins,flavonoids and malondialdehyde did not change significantly,suggesting that the increase of resistance of Populus deltoides was caused by cadmium,not by the change of resistant substances.The effectiveness of the elemental defense hypothesis has been proved in woody plants.（3）In this experiment,the physical and chemical properties of poplar of different sexes were different.The growth index of male poplar was higher than that of female poplar in control treatment,and the absorption of cadmium by male poplar was significantly higher than that of female poplar in cadmium treatment.Generally speaking,the tolerance and accumulation of cadmium in male Populus deltoides were higher than that in female.At the same time,the study found that the disease index of poplar was correlated with the sex of poplar,and male poplar was more resistant to disease.Poplar plantations can be constructed by differentiating the sex of poplar trees to obtain a better growth forest.For different cadmium-contaminated sites,poplar plants of suitable sex should be selected for afforestation and ecological restoration according to the situation.