Growth, morphology and gas exchange of mycorrhizal and nonmycorrhizal Panicum coloratum L., a C4 grass species, under different clipping and fertilization regimes.

Root samples collected in grasslands of the Serengeti ecosystem, Tanzania, were found to be mycorrhizal and infection frequency was positively correlated with grazing intensity across sites. To examine the role of mycorrhizae in a grazing ecosystem, I analyzed the growth, morphology and gas exchange of mycorrhizal and nomycorrhizal plants of Panicum coloratum L. under different fertilization and clipping regimes. Both severe clipping and high nitrogen promoted more prostrate shoot growth but inhibited root growth. However, mycorrhizal infection promoted a prostrate shoot morphology and enhanced root growth. Photosynthesis was inhibited by clipping, however; at the most severe clipping and nitrogen regime, photosynthesis of the mycorrhizal plants was not affected whereas the largest inhibition of photosynthesis occurred in similarly treated nonmycorrhizal plants. Discussion of the putative roles of mycorrhizae in intensely grazed ecosystems is presented.