OBSERVATION OF VESICULAR-ARBUSCULAR MYCORRHIZAL FORMATION IN THE ROOTS OF SOME SEASONAL WEEDS PROLIFERATED IN CITRUS ORCHARDS

Weeds were collected from citrus orchards in April and July to investi gate vesicular-arbuscular mycorrhizal (VAM) infection. The infection w as found to be high in the roots of spring weeds: Rumex acetosa L., Ag ropyron tsukuhiense (Honda) Ohwi var. transiens (Hack.) Ohwi, Stellari a media Villars., Vicia cracca L., Lamium amplexicaule L., and Medicag o polymorpha L., and in the roots of summer weeds: Erigeron canadensis L., Amaranthus lividus L., Cynodon dactylon (L.) Pers., Beckmannia sy zigachne (Steud.) Fern., Commelina communis L., Oxalis corniculata L., and Digitaria adscendens Henr. Spore formation was mostly found in th e roots of spring weed: Stellaria media, Vicia cracca, and Lamium ampl exicaule; no VAM infection was observed in the roots of Rumex japonicu s Houtt., Equisetum arvense L., and Polygonum blumei Meisn.