Physiological Response Of Helianthus Tuberosus L.under Cadmium Stress And Improvement Of Polluted Red Soil

The Cd pollution in soil involves a wide area and brings a large harm.In view of the currently serious Cd pollution in soil,phytochemical remediation are characterized as targeted and green.In this paper,Using soil culture and select resistant Helianthus tuberosus L.(2 cultivars of Helianthus tuberosus from Weifang and Xuzhou)as the research object,to explore the physiological characteristics,such as growth,photosynthesis,defense enzyme system and Cd absorption and transfer characteristics of Helianthus tuberosus under different Cd stress(Ommol/L(CK)、0.1 mmol/L(T0.1)、0.5mmol/L(T0.5)、1.Ommol/L(T1)).At the same time,lime and NPK fertilizers(CO(NH2)2,KH2PO4,K2SO4)were used to improve the Cd-polluted red soil in order to study the impact of soil physical and chemical properties change on the growth and Cd enrichment of Helianthus tuberosus under Cd stress(1.0mmol/L(T1)).The main results as follows:1.Impact of Cd on physiological characteristics of Helianthus tuberosusThe impact of Cd on physiolog of Helianthus tuberosus was related to the Cd concentration,treatment time and cultivars of Helianthus tuberosus.On the 7th day,the content of SPAD,Fv/Fm,ETR,qP and MDA in the leaves of Cd treatment groups in 2 cultivars of Helianthus tuberosus had no significant change as compared with the control group,and the antioxidant enzymes activities generally presented an upward trend,T0.5 and T1 group is increased significantly than CK group(P<0.05).On the 21st day,the SPAD,fluorescence parameters,antioxidant enzyme activities and root activities of 2 cultivars of Helianthus tuberosus decreased against the increase of Cd concentration.Among them,the SPAD,root activity and SOD of Helianthus tuberosus(Weifang)T1 group dereased by 19.32%,17.12%,33.66%compared with CK group.but the MDA content and the relative plasmamembrane permeability of roots presented a positive correlation with Cd stress.In general,under the same Cd stress,the MDA content of Helianthus tuberosus(Weifang)was higher than Helianthus tuberosus(Xuzhou),and SOD,CAT and root activities decreased significantly.It can be seen from various indexes that,when the Cd stress was small,2 cultivars of Helianthus tuberosus can strengthen root activities,increase antioxidant enzyme activities,reduce membrane lipid peroxidation to resist Cd stress.However,the greater the Cd stress was,the weaker the resistance,which was more obvious in Helianthus tuberosus(Weifang).2.DNA damage by Cd on Helianthus tuberosus’s rootsUsing comet assays to get comet pictures of DNA,and then use GASP software to analyze the relevant parameters of comet DNA.the results showed that the DNA damage by Cd on roots was directly related to the Cd concentration.Under low Cd treatment,a short and dark tail appeared on the comet head;as the Cd concentration increased,the fluorescence of the tail improved,For related parameters,such as Tail Length,Tail DNA,Tail Moment and Olive Tail Moment increased,Helianthus tubersus(Xuzhou)T]group is 2.14,4.16,1.96,1.73 times that of the T0.1 group.Comparing the OTM size of 2 cultivars of Helianthus tuberosus,it was found that under low Cd stress,the Olive Tail Moment of Helianthus tuberosus(Weifang)was larger,but under high Cd stress,the opposite was true.This indicted that under the same Cd stress,the oxidative damage of 2 cultivars of Helianthus tuberosus was different,and Helianhus tuberosus(Weifang)was more sensitive to Cd.3.Study on accumulation and transfer of Helianthus tuberosus on CdIn view of the Cd accumulation,the Cd accumulation is positively correlated with the concentration of Cd.Helianthus tuberosus(Xuzhou)T1 group was 1.62 times higher than T0.1 group,while Helianthus tuberosus(Weifang)reached 3.90 times.under the same conditions,the Cd enrichment ability of Helianthus tuberosus(Xuzhou)was better.As far as Cd transfer coefficient was concerned,the transfer coefficient of 2 cultivars of Helianthus tuberosus was less than 1,which directly affected the Cd accumulation in different parts of Helianthus tuberosus.The roots were the main organs to accumulate Cd,and then it was followed by stems and leaves.There was certain difference on Cd accumulation in stems and leaves for 2 cultivars of Helianthus tuberosus.The Cd content in the stems of Helianthus tuberosus(Weifang)was higher than that in the leaves,and the opposite was true fo Helianthus tuberosus(Xuzhou).This revealed the difference in the retention degree of Cd during the xylem transfer process of 2 cultivars of Helianthus tuberosus,reflecting cultivars difference between them.4.Impact of lime and NPK fertilizers on physicochemical properties of Cd-polluted red soil and on Cd enrichment of Helianthus tuberosusUnder the action of lime,the pH of Cd-polluted soil increased significantly,reach 6.5,increasing by nearly 30%.NPK fertilizer significantly improved the content of soil organic matter,cation exchange capacity,soil alkali-hydrolyzable nitrogen,rapidly available phosphorus and rapidly available potassium,but it had little effect on soil pH.The oil organic matter cotent of NPK group in 2 cultivars was 2.10 times higher than lime group.The application of lime and NPK fertilizers significantly reduced the Cd enrichment of the in Helianthus tuberosus,and the effect of lime was stronger.As far as Cd transfer coefficient of Helianthus tuberosus was concerned,both soil conditioners promoted the Cd transfer of Helianthus tuberosus(Xuzhou),but weakened Helianthus tuberosus(Weifang).5.Impact of lime and NPK fertilizers on growth and physiological characteristics of Helianthus tuberosus under Cd stressTwo soil modifiers have some mitigative effects on the physiological stress of Helianthus tuberosus under cadmium treatment.NPK fertilizer had obvious effect in chlorophyll content and plant height,while lime has a greater impact on the antioxidant enzyme activities.There was difference in effect between NPK fertilizer and lime.NPK fertilizer increasing the content of rapidly available NPK in soil,promoted Helianthus tuberosus to absorb more nutrients,which would accelerate growth and enhance resistance;however,lime would increase the pH in the Cd-polluted soil to reduce the bioavailability of Cd,so as to weaken the toxicity on Helianthus tuberosus and maintain the normal growth of Helianthus tuberosus.