Mycorrhizal infection in Pennine grassland. 2. Effects of mycorrhizal infection on the growth of some upland grasses on gamma -irradiated soils.
Abstract
The effects of mycorrhizal infection on the growth of 5 upland grass spp. (Anthoxanthum odoratum, Cynosurus cristatus, Festuca rubra, Nardus stricta and Agrostis tenuis) were assessed using 3 soils partially sterilized by gamma -irradiation. Glomus tenuis was the dominant endophyte in grasses that received a mixed mycorrhizal inoculum. Mycorrhizal infection did not significantly increase plant dry wt. after 20 wk and frequently depressed it. However, mycorrhizal infection did increase plant dry wt. and the shoot P content of grasses grown for 19 months on the soil with least available P. Grasses inoculated with G. mosseae formed mycorrhizas on only one soil, and after 43 wk the infected plants were smaller than the controls but had higher shoot P contents. The generally negative effects of mycorrhizas on grass growth can probably be attributed initially to the greater availability of nutrients in irradiated soil. The fine much-branched root system of grasses permits efficient uptake of P and mycorrhizal uptake is not significant until the soil is very severely depleted.<new para>ADDITIONAL ABSTRACT:<new para>Glomus tenuis was the dominant endophyte in grasses that received a mixed mycorrhizal inoculum. Mycorrhizal infection did not significantly increase plant dry wt. after 20 weeks and frequently depressed it, but it did increase dry wt. and shoot phosphorus of grasses grown for 19 months on soil with least available phosphate. Grasses inoculated with G. mosseae formed mycorrhizas on only 1 soil, and after 43 weeks the infected plants were smaller than the controls but had higher shoot phosphorus percentage. The generally negative effects of mycorrhizas on grass growth can probably be attributed initially to the greater availability of nutrients in irradiated soil. The fine, much-branched root system permits efficient uptake of phosphate, and mycorrhizal uptake is not significant until the soil is very severely depleted.