Abstract
The effect of inoculating seedlings of asparagus (Asparagus officinalis L.) with the arbuscular mycorrhizal (AM) fungus (Glomus etunicatum) on their growth and N, P, K, Ca and Mg contents was investigated.
AM fungus infection became distinct approx. 7 days after inoculation. Arbuscules (the organs of nutrient transfer between the host and fungus) and vesicules (fungal storage organs) were formed approx. 12 and 32 days after inoculation, respectively. The rate of AM fungusinfected portions in a whole root system (percentage of total portions in-fected with AM fungus in a whole root system) increased most rapidly between 2 and 4 weeks after inoculation.
The emergence of shoots and roots and their elongation were promoted by host-fungus symbiosis, especially after the second emergence. Dry weights became greater in AM fungus-infected plants than in noninoculated plants after a lapse of 4 weeks from inoculation.
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 in-creased considerably 4 weeks after inoculation, particularly in the 3rd and 4th shoots, the 1st and 2nd roots, and the rhizome including buds. The available-P concentration in bed soil used for raising infected plants decreased more rapidly than that for raising noninoculated plants.
These results indicate that, in asparagus seedlings, the growth enhancement due to AM fungus infection was mainly caused by the increase of phosphorus concentrations in the plants.
