Research On The Effect Of DA-6 Alleviating Continuous Cropping Obstacles In Melon Seedling Stages

This research takes the melon non continuous cropping soil as the control,and uses continuous cropping soil-potted Japanese melon varieties "Wutu" for 5 years and 15 years to study the impact of the content of nutrient elements and the diethyl aminoethyl hexanoate in the soil sample under continuous cropping stress(referred to as DA-6 in short)treatment on melon seedling growth,antioxidant system and photosynthetic characteristics.The results are as follows,1.Under continuous cropping stress,soil pH and total nitrogen content gets increased significantly and gets increased more obviously for continuous cropping 15 years than 5 years;the organic matter content,Fe content,the Cu content and Zn content becomes significantly reduced and continuous cropping 15 years declines more obviously than 5 years.2.Under the continuous cropping stress,the leaf area,fresh weight and dry weight of the melon seedlings become significantly reduced,increasing more obviously for continuous cropping 15 years than 5 years.There was no significant difference of Melon Seedlings in the plant height under different continuous cropping years.After spraying DA-6 solution of different concentrations to compare with the control,seedling's leaf area,fresh weight and dry weight get significantly increased and when the spraying concentration is8 mg·L-1,the melon seedling's leaf area,fresh weight and dry weight reach the maximum.Spraying DA-6 solution of different concentrations has no significant effect on the plant height of melon seedlings.3.Under continuous cropping stress,the activity of peroxidase(POD)and superoxide dismutase(SOD)in the leaves of melon seedlings becomes significantly decreased.After the treatment of DA-6 solution,the activity of SOD and POD becomes increased obviously.At the same time,the content of malondialdehyde(MDA)in the melon seedling's leaves becomes significantly increased under the continuous cropping stress.After spraying DA-6 solution,MDA content becomes decreased significantly,and when the spraying concentration of DA-6 solution is 8 mg·L-1,the activity of POD and SOD in the melon seedling's leaves becomes the largest,and the MDA content is the least.4.Under continuous cropping stress,the chlorophyll content in the melon seedling's leaves becomes decreased significantly,declining more obviously for continuous cropping 15 years than 5 years;the content of the chlorophyll a(Chla),chlorophyll b(Chlb)and chlorophyll(Chla+b)all becomes decreased significantly.The photosynthetic melon seedling leaf net photosynthetic rate(PN),stomatal conduction degree(GS),and transpiration rate(TR)with the increase of continuous cropping years becomes significantly decreased,with the intercellular CO2 concentration(CI)increased and the actual photochemical efficiency(Y(?))decreased significantly,non photochemical quenching coefficient(QN)significantly increased;the difference of initial fluorescence Fo,Fv/FM and qP of melon seedling's leaves in continuous and non continuous cropping soil is not obvious.Spraying DA-6 solution treatment can effectively improve Chla,Chlb,Chla+b and carotene content in the melon seedling leaf and improve the actual photosynthetic rate(Y(?))and reduce qN,and at the same time Pn,Gs and Tr becomes significantly increased,with Ci decreased obviously and when spraying theDA-6 concentration is 8 mg·L-1,the effect is the best.There is no significant difference in the initial fluorescence of Fo,ETR,Fv/Fm and qP in melon seedling's leaves with different concentration of DA-6 solution.