Effects of continuous cropping on plant morphology and physiological characteristics of tartary buckwheat seedlings under hydroponics

【Objective】The purpose of the study was to explore the effect of continuous cropping on the growth of tartary buckwheat seedlings and differential response of different tartary buckwheat varieties to continuous cropping obstacles,and to provide theoretical and technical support for high-yield cultivation of tartary buckwheat.【Method】 Two tartary buckwheat varieties, Jiujiang buckwheat and Jinqiao 2, were used as experimental materials. Under the condition of hydroponics, continuous cropping was carried out for 6 times,including 0(CK),1(C1),2(C2),3(C3),4(C4)and 5(C5). The effects of each continuous cropping treatment on the morphological and physiological characteristics of tartary buckwheat seedlings were comparatively analyzed.【Result】 The plant height,plant fresh weight,total root length,root surface area,root activity,chlorophyll and soluble protein content in leaves of Jiujiang buckwheat and Jinqiao 2 all showed a continuous decreasing trend with the increase of continuous cropping times,among which the root surface area decreased the most, compared with CK, Jiujiang buckwheat and Jinqiao 2 decreased by 79.28% and 68.81% respectively in C5 treatment. The activities of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) in tartary buckwheat leaves increased at first and then decreased with the increase of continuous cropping times. The activities of SOD,POD and CAT in Jiujiang buckwheat leaves reached the maximum in C2 treatment,while that of Jinqiao 2 leaves reached the maximum in C3 treatment. The contents of malondialdehyde(MDA)and superoxide anion radical in tartary buckwheat leaves gradually increased with the increase of continuous cropping times. Compared with CK,the content of MDA in C5 treatment of Jiujiang buckwheat and Jinqiao 2 increased by 36.34% and 25.04% respectively, and the content of superoxide anion radical in C5 treatment of Jiujiang buckwheat and Jinqiao 2 increased by 77.82% and 52.87% respectively. With the increase of continuous cropping times,the contents of chlorophyll and soluble protein in the leaves of two tartary buckwheat varieties decreased continuously. The chlorophyll content of Jiujiang buckwheat and Jinqiao 2 in C5 treatment decreased by 70.96% and 54.09% respectively,and the soluble protein content decreased by 38.89% and 32.23%,respectively.【Conclusion】 Continuous cropping will affect the growth of tartary buckwheat seedlings to certain extent,and there are differences among buckwheat varieties in their responses to continuous cropping obstacles. In general,Jiujiang buckwheat is more affected by continuous cropping obstacles than Jinqiao 2.