Uptake and Partitioning of Nitrogen by Maize Infected withStriga hermonthica

The uptake and partitioning of nitrogen (N) by maize infected with the parasitic angiosperm, Striga hermonthica was investigated in sand culture in a glasshouse. The purpose was to determine the effect of Striga on N uptake and partitioning in maize. Maize was grown at 22, 66 and 133 mg N per plant and sampled five times. There was no significant Striga ×N interaction in any measured response. Leaf dry matter of Striga -infected maize, averaged over all N treatments, was 92% that of uninfected maize at the four-leaf stage but by the 18-leaf stage it had decreased to 58%. Similarly, stem dry matter of infected maize which was 91% that of uninfected maize at the four-leaf stage was only 42% at the 18-leaf stage. Root dry matter was similar for infected and uninfected maize. N concentration in the leaf, stem and root declined asymptotically from the first to the last sampling date for both infected and uninfected maize. The asymptotic value of N concentration in Striga -infected maize was 16% greater in the leaf, 55% in the stem, and 21% in the root than in uninfected maize. The concentration of N in Striga was higher than in maize at the 16- and 18-leaf stages. Uptake of N was similar for infected and uninfected plants at the four–eight leaf stage but at the eight–12 leaf stage, N uptake by infected maize was 52% that of uninfected maize. However, the proportion of total plant nitrogen partitioned to the root was greater ( P <0.001) for Striga -infected maize. These results showed that the extent to which S. hermonthica reduced maize growth and N uptake, but increased the proportion of N partitioned to the roots, did not depend on the rate of N fertilizer applied.