Effects of several vesicular-arbuscular mycorrhizal (VAM) fungi on shoot growth and mycorrhizal development in ‘Citation’ perennial ryegrass (Lolium perenne L.) were studied as a function of inoculum placement depth. Soil columns were layered with inoculum at 0, 5, 10, or 20 cm prior to seeding. Three inocula were tested: 1) chopped roots and soil from sorghum (Sorghum bicolor L.) plants previously infected with the VAM fungus Glomus macrocarpus Tul. and Tul. var. macrocarpus; 2) a mixed inoculum from plants infected with G. macrocarpus var. macrocarpus; G. mosseae (Nichol. and Gerd.), G. faciculatum (Thaxter) Gerd. and Trappe, Gigaspora margarita Becker and Hall; 3) roots and soil from noninoculated sorghum plants. Shoot growth was greatest when VAM inoculum was placed at the surface, and declined progressively with deeper placement. Greatest mycorrhizal fungal infection of the root system occurred at the site of inoculum placement regardless of depth. The effectiveness of the surface-applied inoculum on enhancing the initial shoot growth (70 days) of perennial ryegrass in this study suggests that inoculation with VAM fungi might prove useful in low maintenance turfgrass culture.
Root lengths of an adventitious root system (creeping bentgrass, Agrostis palustris Huds.) and a woody plant fiberous root system (Hetz juniper, Juniperus chinensis L. ‘Hetzii’) were estimated using an automated method employing a video camera and an area/length meter to count scanning line and root intersections. A grid method of root length estimation was used for comparison. Under- and overestimation was random when the automated method was used for creeping bentgrass samples (<80 cm) and the shorter group of juniper root samples (150-550 cm). However, these estimates were much closer to the actual root length, in the ranges evaluated, than the estimates from the grid method. The lengths of long juniper root samples (600-3000 cm) were underestimated consistently with the automated method. The magnitude of this underestimation increased with increasing length. However, the relationship between estimated and actual root length remained linear and was about 76% of the actual length. For the ranges of root length evaluated, this method was found to be useful for root length estimation.