Cross‐colonization of Scots pine (Pinus sylvestris) seedlings by the ectomycorrhizal fungus Paxillus involutus in the presence of inhibitory levels of Cd and Zn

Abstract

The effects of Cd and Zn on cross-colonization by Paxillus involutus of Scots pine seedlings was examined by using pairs of ectomycorrhizal (ECM) and non-mycorrhizal (NM) seedlings grown in the same vessel. This was done to assess, first, the ability of P. involutus to colonize NM Scots pine seedlings by growth from colonized roots of other Scots pine seedlings in the presence of Cd or Zn, and, second whether ECM colonization of Scots pine by P. involutus provided a competitive advantage over NM seedlings. Ectomycorrhizal colonization of Scots pine was shown to be more sensitive than Scots pine itself to Cd and Zn, but prior colonization did provide a competitive advantage with respect to biomass production. This beneficial effect over NM seedlings was, however, equal in the control, Cd and Zn treatments, and was due simply to growth stimulation in the presence of ECM colonization. Cross-colonization from an ECM to a NM seedling was reduced but not prevented by Cd and Zn. Cd had a more negative effect on cross-colonization than on initial colonization of seedlings, whereas Zn had an equally inhibitory effect on both parameters. These results have important implications for plant establishment on metalcontaminated sites. If cross-colonization between plants is reduced by toxic metals, plant establishment on contaminated sites might be retarded.

Mycorrhizal fungi and ectomycorrhiza associated bacteria isolated from an industrial desert soil protect pine seedlings against Cd(II) impact

“…The data indicate that mycorrhization efficiency may depend on specific interactions between fungal species and associated bacteria. Moreover, root colonization is determined by recognition and compatibility between plant host and fungus (Hartley et al 1999).…”

“…After germination, the root systems of the seedlings were dipped in the bacterial suspensions for 20 min followed by transferring of the seedlings to polyethylene pots containing 150 g of autoclaved soil, prepared according to Kawai (1997), thoroughly mixed with fungal inoculum in ratio 15:1 (v/v). In total, 80 plants, one seedling per pot, were kept in a plant growth cabinet with a 14 h photoperiod (daylight Pine mycorrhization against Cd(II) impact 451 supplemented with artificial light), 70% relative humidity, and day and night temperatures of 23°C and 18°C (Hartley et al 1999), respectively for 3 months. The seedlings were wetted with water within first 2 weeks, then they were wetted twice a week (100 ml) with Cd(II) as CdCl 2 at concentration of 10 lg Cd(II) ml -1 .…”

Genetic variation and heavy metal tolerance in the ectomycorrhizal basidiomycete Suillus luteus

“…A laboratory experiment of Hartley et al (1999) suggests that there is only a minor difference in Zn and Cd sensitivity of Scots pine and its mycobiont Paxillus involutus. In Lommel, the pine trees were able to establish because of the application of soil additives in the planting holes.…”

Toxic effects of cadmium and zinc on ectomycorrhizal colonization of scots pine (Pinus sylvestris L.) from soil inoculum

“…The role that ECM fungi play in the metal sensitivity of plants, however, is less clear [4]. Some authors report that ECM fungi confer tolerance to their host plants [1, 18], whereas others report that the beneficial effect of ECM colonization is equal in both normal and contaminated environments [11, 19]. Results from this study show that Cd and Zn are more toxic to ECM fungal infection than to Scots pine seedlings themselves, with minimal effects on shoot biomass and total root‐tip density and a lesser effect on root biomass than on ECM infection levels.…”

“…Successions of ECM fungi on plant roots rely on cross‐colonization from other plant roots or on colonization from propagules in the soil [10]. A recent study of ECM Scots pine showed that whereas cross‐colonization from one plant to another can occur in the presence of Cd and Zn for single ECM fungal isolates in vermic‐ulite culture, the process is partially inhibited by both metals [11].…”