Nitrogen efficiency and metabolism in grafted melon plants

Three cultivars of Cucumis melo (Yuma, Melina and Gallicum) were grafted onto three Cucurbita maxima x moschata cultivars (Shintoza, RS-841 and Kamel), resulting in nine treatments of the corresponding crosses between stock and scion parts. In addition, for each scion cultivar, one was ungrafted and used as a control. The plants were grown under controlled conditions and constantly fertilized with macro and micronutrients. Nitrate (NO3-), nitrate reductase activity (NRA), concentrations of amino acids, proteins and organic nitrogen (N), and fruit yield were measured for all the scion parts of the plants. The results show considerable differences between controls and grafted plants. Controls presented high concentrations of (NO3-), lower NRA and greater contents of total free amino acids and soluble proteins, whereas organic N and fruit yield increased significantly in the majority of the grafted plants. These changes could be attributed to the differences in N utilization and assimilation between grafted and control plants, caused principally by the effect of the interaction and of the rootstocks in the grafted plants. (C) 1999 Elsevier Science B.V. All rights reserved.