C and N Mobilization from Stalk and Leaves during Kernel Filling by C and N Tracing in Zea mays L.

The sink capacity of the stalk in Zea mays L. (cv DEA) during the elongation period was previously investigated with (13)C and (15)N tracing. The chase experiment described here demonstrates the different behavior of intermediary reserves for C and N remobilization until full maturity of the kernels. Carbon incorporated during stalk elongation participated mainly in cellulose formation in vegetative organs appearing after the labeling period; the remobilization to kernels was low (0.5%). Soluble carbohydrates and proteins were the main intermediary sink compounds, starch being little remobilized. N first incorporated in roots, sheaths, stalk, blades was translocated to the kernel; 42% of the labeled N were recovered in kernels where they represented 8% of the total N. Cob, husk, and shank acted first as N sinks and then as N sources during ear development. It appeared that aminoacids used for synthesis of kernel proteins have a common origin, except for glutelin G(3).