Research on effects of continuous cropping on the growth,physiological characteristics and autotoxic substances of Codonopsis pilosula var.modesta
In order to explore the continuous cropping obstacle effect of Codonopsis pilosula var.modesta and its mechanism,pot experiments were conducted in the soil of normal crop(CK),and continuous cropping 1 year(CC1),continuous cropping 2 years(CC2)and continuous cropping 3 years(CC3)as experimental objects.The effects of continuous cropping on the growth,antioxidant enzyme system and chlorophyll of C.pilosula var.modesta were evaluated,and the types and levels of autotoxic substances in the soil of different continuous cropping years were analyzed by gas chromatography-mass spectrometry(GC-MS).The results showed that continuous cropping had an inhibitory effect on the growth of C.pilosula var.modesta at the seedling stage,flowering stage,peak growth stage and harvest stage,and the effect gradually strengthened with increase in the number of continuous cropping years.In the same continuous cropping years,with the advancement of growth process,the activities of catalase(CAT)and superoxide dismutase(SOD)in leaves initially increased and then decreased,and the activities of peroxidase(POD)initially decreased and then increased and then decreased again,but at the same growth stage,the activities of the three antioxidant enzymes all decreased year by year,and but the levels of malondialdehyde(MDA),proline(Pro),soluble sugar and the relative conductivity all increased year by year.The results of GC-MS showed that 5,17,13 and 4 chemical substances were identified from CK,CC1,CC2 and CC3,respectively,including di-2-ethylhexyl phthalate,dibutyl phthalate,ethyl propionate and oleamide,among which di-2-ethylhexyl phthalate was found in all treatments with relatively high levels.It can be seen that continuous cropping can inhibit the growth of C.pilosula var.modesta by disrupting the antioxidant enzyme system and reducing the leaf chlorophyll content,resulting in continuous cropping disorders.The autotoxicity under continuous cropping is one of the main causes for continuous cropping disorders in C.pilosula var.modesta.
Codonopsis pilosula var.modestacontinuous cropping obstaclesphysiology and biochemistryallelopathic autotoxicitygas chromatography-mass spectrometry
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