THE INFLUENCE OF NITROGEN ON GROWTH AND PHOTOSYNTHESIS OF SORGHUM INFECTED WITH STRIGA-HERMONTHICA FROM DIFFERENT PROVENANCES

The influence of Striga hermonthica on sorghum growth and photosynthesis is dependent on the provenance of the parasite seed. Inter-provenance differences are correlated with emergence time of the parasite above ground, as well as with the mass (but not number) of Striga hermonthica plants supported by the host. The greater effects of early attachment on host growth and photosynthesis were demonstrated by inoculating S. hermonthica plants to both 3-day-old and 19-day-old hosts. There were statistically significant interactions between nitrogen supply and provenance on the relationship between (1) host biomass and parasite biomass and (2) photosynthetic impairment and parasite biomass. There was no statistically significant interaction between nitrogen supply and provenance on the relationship between host biomass and parasite emergence time. Thus, nitrogen may influence provenances through processes which occur post-germination. Potential explanations for inter-provenance difference on these later processes are discussed.