EFFECT OF CONSTANT AND DIURNALLY FLUCTUATING TEMPERATURES ON ARBUSCULAR MYCORRHIZAL FUNGUS INFECTION AND THE GROWTH OF INFECTED ASPARAGUS (ASPARAGUS-OFFICINALIS L) SEEDLINGS

Effect of constant and diurnally fluctuating temperatures on arbuscula r mycorrhizal (AM) fungi [Glomus etunicatum (GE) and Gigaspora margari ta (GM)] infection and the promotion of infected seedling growth throu gh asparagus-AM fungus symbiosis were investigated. 1. At constant tem peratures, spore germination rate became maximum at 25 degrees C in GE , and at 25 degrees and 30 degrees C in GM. Hyphal growth was enhanced at 20 degrees, 25 degrees and 30 degrees C in GE, and at 25 degrees, 30 degrees and 35 degrees C in GM. 2. Under constant bed soil of 20 de grees, 25 degrees and 30 degrees C for 8 weeks after inoculation, ther e was no growth enhancement at 20 degrees C regardless of the AM fungu s species; whereas at 25 degrees and 30 degrees C, the GE- and GM-inoc ulated plants were taller than the noninoculated plants. At 30 degrees C, the GM-inoculated plants were taller than those inoculated with GE . At 25 degrees C, the GE-or GM-inoculated plants had the most shoots and storage roots than did those at other temperatures. The rate of AM fungus-infected portions in a whole root system (as percentage of the total portions infected with AM fungus in a whole root system) was ma ximum at 25 degrees C in GE-inoculated plants but at 25 degrees and 30 degrees C in GM-inoculated ones. 3. Under the bed soil temperature co nditions diurnally fluctuating in the range of 25 degrees C to 15 degr ees C and 30 degrees C to 18 degrees C, 8 weeks after inoculation, the plants were taller and had more numerous shoots and storage roots in GE-inoculated plants than in GM-inoculated ones in a regime between 25 degrees C and 15 degrees C; the reverse was noted in a regime between 30 degrees C and 18 degrees C. Little difference in the rate of AM fu ngus-infected portions in a whole root system was recognized between t he two temperature regimes in GE-inoculated plants, whereas in GM-inoc ulated ones, the rate became higher at the temperature fluctuated betw een 30 degrees C and 18 degrees C than it did at the temperature fluct uated between 25 degrees C and 15 degrees C.Consequently, it seems tha t in asparagus, the optimum temperature range for infection and the pl ant growth enhancement through symbiosis differed between Glomus etuni catum and Gigaspora margarita.