Abstract:

Continuous cropping is one of the main factors that affect the peanut yield. There are about 250 000 ha continuous cropping areas with a yield loss of about 110 000 t every year in Shandong province. Understanding the effect of continuous cropping on peanut photosynthesis and metabolism is very important to explore the yield-reducing reasons and relieve the loss of continuous cropping. In this study, photosynthetic performance of three peanut cultivars (8130, from Virginia; Luhua 12, from Spanish; Luhua 14, from interspecies crossing) was compared in field experiments with two farming patterns of continuous cropping(CP)and rotation cropping (RP) and the reactive oxygen metabolizing feature of plant under different cropping modes (One-year continuous cropping, T1; two-year cropping, T2; rotation cropping, T0) was observed using pool test to understand the mechanism of CP press on growth and development of peanut. Results showed that CP press of peanut significantly decreased the rate of leaf net photosynthesis（P_n）and canopy apparent photosynthesis (CAP) , as well as leaf area index（LAI）, while little influenced chlorophyll (Chl) content. Significant positive correlations of LAI with CAP and with crop growth rate (CGR), as well as Chl content with P_n were observed. Therefore, the decrease of LAI was the dominant factor that hampered dry mass accumulation and lowered pod production in CP peanut. Sensitivity of different peanut variety types to CP press was evident: Luhua 12 >Luhua14>8130. The change of all the characters mentioned above became larger with the plant development. CP decreased the activities of SOD, POD, and CAT, and increased MDA content in leaf, and the changes were larger when the year of CP increased. CGR was significantly correlated with activities of POD and SOD in leaves and not correlated with MDA, CAT and soluble protein. The activity decrease of protective enzyme, such as POD and SOD, was one of the reasons for poor growth and development and early senescence in CP peanut.

Key words: Peanut, Continuous cropping, Photosynthesis, Metabolism of reactive oxygen, Variety type