Roots were cleared in 10% KOH for 45 min at 80 ◦C, rinsed in tap
water and immersed in 2.5% HCl for 30 min. Subsequently roots
were stained with Trypan blue (Sylvia, 1994). Mycorrhizal colonization
was estimated on slides according to the improvedmethod
described by McGonigle et al. (1990)