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

Effects of improved iron nutrition of peanut intercropped with maize on carbon and nitrogen metabolism and nitrogen-fixing of peanut nodule

研究了石灰性土壤上玉米 (Zea mays L.) /花生 (Arachishypogaea L.)混作改善花生铁营养对花生光合速率、光合产物的运输、花生各部位糖类含量、固氮酶活性以及根瘤内碳氮代谢及其有关酶活性的影响。结果表明 ,玉米 /花生混作改善花生铁营养能够明显增强固氮酶活性 ,进而增加了间作花生根瘤氨基酸的含量 ,这主要是由于玉米 /花生混作改善花生铁营养促进了花生光合作用 ,提高光合产物数量 ,增加光合产物由地上部向地下部的运输 ,但是处理间花生根瘤蔗糖和可溶性糖含量变化不大 ,单作花生根瘤还积累较多淀粉 ,说明不是光合产物的供应导致了花生固氮活性的差异。玉米 /花生混作对花生根瘤碳水化合物代谢水平影响较大 ,混作花生根瘤异柠檬酸脱氢酶 (IDH)、苹果酸脱氢酶 (MDH)、琥珀酸脱氢酶活性明显高于单作 ,而磷酸烯醇丙酮酸羧激 (PEPCK)活性低于单作花生 ,表明混作花生根瘤内三羧酸循环代谢水平较高 ,形成类菌体直接吸收利用的能量物质苹果酸和琥珀酸多 ,能够满足类菌体的固氮需求 ,因此 ,玉米

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.