UPTAKE AND PARTITIONING OF NITROGEN BY MAIZE INFECTED WITH STRIGA-HERMONTHICA

The uptake and partitioning of nitrogen (N) by maize infected with the parasitic angiosperm, Striga hermonthica was investigated in sand cul ture in a glasshouse. The purpose was to determine the effect of Strig a 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 S triga x N interaction in any measured response. Leaf dry matter of Str iga-infected maize, averaged over all N treatments, was 92% that of un infected 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 w as 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 uninf ected maize. N concentration in the leaf, stem and root declined asymp totically from the first to the last sampling date for both infected a nd 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 w as similar for infected and uninfected plants at the four-eight leaf s tage but al the eight-12 leaf stage, N uptake by infected maize was 52 % that of uninfected maize. However, the proportion of total plant nit rogen partitioned to the root was greater (P < 0.001) for Striga-infec ted maize. These results showed that the extent to which S. hermonthic a 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. (C) 1998 Annals of Botany Company.