EFFECT OF ARBUSCULAR MYCORRHIZAL FUNGUS I NFECTION ON GROWTH AND MINERAL NUTRIENT CONTENT OF ASPARAGUS-OFFICINALIS L SEEDLINGS

The effect of inoculating seedlings of asparagus (Asparagus officinali s L.) with the arbuscular mycorrhizal (AM) fungus (Glomus etunicatum) on their growth and N, P, K, Ca and Mg contents was investigated. AM f ungus infection became distinct approx. 7 days after inoculation. Arbu scules (the organs of nutrient transfer between the host and fungus) a nd vesicules (fungal storage organs) were formed approx. 12 and 32 day s after inoculation, respectively. The rate of AM fungus-infected port ions in a whole root system (percentage of total portions infected wit h AM fungus in a whole root system) increased most rapidly between 2 a nd 4 weeks after inoculation. The emergence of shoots and roots and th eir elongation were promoted by host-fungus symbiosis, especially afte r the second emergence. Dry weights became greater in AM fungus-infect ed plants than in noninoculated plants after a lapse of 4 weeks from i noculation. The 5 mineral nutrients contents, especially that of P per plant, were increased by the infection, with or without the increase in nutrient concentration. P concentrations increased considerably 4 w eeks after inoculation, particularly in the 3rd and 4th shoots, the 1s t and 2nd roots, and the rhizome including buds. The available-P conce ntration in bed soil used for raising infected plants decreased more r apidly than that for raising noninoculated plants. These results indic ate that, in asparagus seedlings, the growth enhancement due to AM fun gus infection was mainly caused by the increase of phosphorus concentr ations in the plants.