The response of ectomycorrhizal (ECM) fungi under water stress induced by polyethylene glycol (PEG) 6000

Abstract

The growth models, diameter growth rates and biomass yield of three ectomycorrhizal (ECM) fungi, Suillus tomentosus (Kauff.) Sing. Snell and Dick, Suillus laricinus (Berk.in Hook.) O. Kuntze and Aminita vaginata (Bull.: Fr.) Vitt., were investigated under water stress induced by polyethylene glycol-6000 (PEG-6000) in pure culture. The results showed that the growth models of the three ectomycorrhizal fungi were not significantly affected by water stress, but the growth rates and biomass were changed. Lower water stress (-0.15 MPa) could stimulate the growth of three ectomycorrhizal fungi, but greater water stress restricted growth, and inhibitory effect became greater with the increasing water stress from -0.30 to -1.37 MPa. Their drought resistance was ordered by S.laricinus>S. tomentosus>A. vaginata. With the increasing water stress (-0.02 ~ -0.73 MPa), the contents of gibberellin (GA) and auxin (IAA) in mycelium reduced from 26.53 to 0 μg g-1 and 180.98 to 0 μg g-1 respectively. S. laricinus accumulated the most (184.36 μg g-1) abscisic acid (ABA) at -0.30 MPa; when water stress was beyond the tolerance of S.laricinus (-0.49 MPa); however, it inhibited the accumulation of abscisic acid (ABA). Key words: Abscisic acid, ectomycorrhizal fungus, phytohormone, water stress.