Regulation Effect Of Exogenous Jasmonic Acid On Cadmium Tolerance Of Helianthus Tuberosus L.

Helianthus tuberosus is a kind of emerging crop with both ecological and economic value.Due to the serious pollution of Cd in China and it gradually acidifies,antioxidant enzyme activity,photosynthesis and osmosis of Helianthus tuberosus are destroyed,about its promotion and cultivation are also hindered.In this paper,jasmonic acid,a plant stress-related hormone,was selected as a mitigation approach under the stress of Cd of H.tuberosus.Firstly,the H.tuberosus produced in 10 different areas were treated at same concentration for 30 days.By means of membership function analysis and cluster analysis,the experimental materials of H.tuberosus in Yulin and Chengdu with significant difference in Cd tolerance and accumulation ability were screened.Used to study the effects of 25?mol/L exogenous JA on the antioxidant capacity,osmotic adjustment,photosynthesis,Cd enrichment and the transport of H.tuberosus under 75,150 and 300mg/kg Cd concentration stress.To explore the regulatory mechanism of exogenous JA on Cd stress from the perspective of plant physiology.The findings are as follows:1.The effects of Cd stress on the emergence rate,plant height,root length,leaf area,transpiration rate?Tr?,net photosynthetic rate?Pn?,and stomatal conductance?Gs?of H.tuberosus in 10 different producing areas were different.And the content of Cd accumulated in each H.tuberosus was also different.The comprehensive evaluation of cadmium resistance?D?obtained by analyzing the average membership function of these eight indicators was less than 1,indicating that they can be used as indicators to evaluate the degree of Cd stress in H.tuberosus,and then cluster analysis can be performed,which was used to test 10 copies of H.tuberosus.Germplasm tolerance to cadmium was divided into three categories:cadmium tolerance,more cadmium tolerance and cadmium sensitivity.Class1 materials:H.tuberosus in Yulin and Chongqing were cadmium-resistant;Class 2 materials:H.tuberosus in Yichun,Ziyang,Weifang and Kaifeng were more cadmium-resistant;Class 3 materials:H.tuberosus in Xuzhou,Baoding,Xianning and Chengdu were cadmium-sensitive.The dominant and inferior species were screened based on the measurement results of various indicators,so the cadmium-tolerant H.tuberosus in Yulin and cadmium-sensitive in Chengdu were selected for the next comparative experiment.2.Under Cd stress,the activities of SOD,POD,and AsA and GSH contents showed a trend that first rose then fell with the increase of Cd concentration.When they were treated at 300 mg/kg Cd concentration for 21 days,all of them dropped sharply to the trough.A single exogenous JA treatment can improve the overall antioxidant index of H.tuberosus with different tolerance.while treated by exogenous JA+Cd,the SOD,POD activity and AsA content of each experimental group increased significantly.However,the GSH content did not change significantly and the change range of cadmium-sensitive Chengdu was larger than that of cadmium-resistant Yulin.which indicated that exogenous JA could effectively regulate the antioxidant enzyme activity,promote the mutual transformation rate of AsA-GSH,and participate in the generation and transformation of GSH under the stress,so as to clear ROS produced by the stress of Cd in vivo,and further improve the tolerance of H.tuberosus.3.With the deepening of Cd stress,content of MDA keep increasing and soluble proteins first increased and then decreased,while proline and soluble proteins continued to decline.Under the single exogenous JA treatment,the contents of proline,soluble sugar and soluble protein of H.tuberosus with different tolerance increased.Combined treatment with JA+Cd,the proline,soluble sugar and soluble protein increased significantly,but MDA content also decreased significantly.However,the proline and soluble sugar contents showed opposite trends with increasing JA treatment time.4.With the increase of Cd concentration,H.tuberosus's leaf area,plant height,SPAD value,Fv/Fm,ETR and Pn were decreasing significantly,instead F0 and qN were increasing,qP and ETR increased first and then decreased,and Gs decreased significantly at the concentration of 300mg/kg Cd,but Ci and Tr had no significant change,which showed the non-stomatal limitation.when added the exogenous JA and Cd,the other indicators?except for the qP?returned to the control group level.Although the Ci also improved,it was not achieved the remarkable level.Which indicate that exogenous JA can maintain the normal photosynthesis in the root of the composite by regulating the participation of gas exchange and chlorophyll fluorescence parameters,so as to ensure the normal growth of the plant.5.With the increase of Cd concentration,Cd content in roots,stems and leaves of H.tuberosus from 2 different places of origin increased significantly,but the enrichment coefficient and transfer coefficient of Yulin increased first and then decreased,while the Chengdu enrichment coefficient continued to decrease,its enrichment coefficients were more than 1 and the transfer coefficients were less than 1.After co-treatment with JA+Cd,it further reduced the Cd²⁺enrichment in H.tuberosus organs and also hindered the transfer of it.Under laser confocal microscope shows that Cd stress intensifies Cd2+enrichment in guard cells near stoma of leaf and inhibits stoma opening.When added the exogenous JA and Cd,the accumulation of Cd²⁺near the stoma was reduced,and the normal morphology of guard cells was restored.