Effects of improved iron nutrition of peanut intercropped with maize on carbon and nitrogen metabolism and nitrogen-fixing of peanut nodule
玉米/花生混作改善花生铁营养对花生根瘤碳氮代谢及固氮的影响

The effects of improved iron nutrition of peanut(Arachis hypogaea L.) intercropped with maize (Zea mays L.) on photosynthesis rate, the transport of products of photosynthesis from shoot to root and nodule, the content of sucrose and soluble sugar in different organs of peanut, carbon and nitrogen metabolism and nitrogen-fixing of peanut nodule and its related enzyme activity were studied on calcareous soil in pot experiment. Iron deficiency chlorosis occurred in the young leaves of peanut in monocropping and was particularly obvious at the flowering stage, while the young leaves of peanut grown in intercropping with maize remained green throughout the experiment. The results showed that improvement of iron nutrition of peanut intercropped with maize could improve nitrogen -fixing activity of peanut and increase amino acid content of peanut nodule. The reasons were that improvement of iron nutrition of peanut intercropped with maize could promote photosynthesis of peanut, increase the amount of products of photosynthesis and hasten the transport of products of photosynthesis from shoot to root. However, the content of sucrose and soluble sugar in the nodule had not significant difference between monocropping and intercropping system. This indicated the change of photosynthesis was not a key reason that lead to reduce nitrogen -fixing activity of peanut nodule. The results showed improvement of iron nutrition of peanut in the intercropping system had great effects on carbon metabolism in the nodule. The activity of IDH, MDH and SDH enzyme in the nodule of intercropping peanut were increased, but PEPCK activity was decreased in the nodule of peanut intercropped with peanut. This indicated TCA cycle activity in the nodule of intercropping peanut was higher than that of monocropping peanut, so malate acid and succinate acid produced was enough to supply bacteriods. These findings confirmed the effects of improvement in iron nutrition of peanut in intercropping system on carbon metabolism of nodule was an important factor which promoted nitrogenase activity of peanut nodule.