Translocation of C^(14)‐Labeled Compounds in Mycorrhizae and It Implications in Interplant Nutrient Cycling

Abstract

Loblolly pine (Pinus taeda L.) seedlings were grown axenically in mycorrhizae synthesis cultures with either the symbiont Pisolithus tinctorius (Pers.) Coker and Couch or Thelephora terrestris (Ehrh.) Fr. Glassware was designed to allow synthesis of mycorrhizae on two seedlings physically separated except for a bridge formed between the two root systems by mycorrhizal fungus mycelium. Glucose—C14 and sucrose—C14 were used as tracers to investigate movement of labeled compounds from mycorrhizal roots to external mycelium, from external mycelium to roots and from one root system to the other via shared mycelium. Whether applied to foliage as glucose—C14 or sucrose—C14, C14 was readily translocated to pine roots. Transport of C14 from mycorrhizal roots to external hyphae of T. terrestris up to a distance of 12 cm was shown, but only slight movement of C14 occurred into external hyphae of P. tinctorius. The introduction of glucose—C14 and sucrose—C14 to isolated strands of T. terrestris resulted in the movement of C14 from strands to roots. Movement of isotope from one seedling to the other via mutually—shared mycelium did not occur in the synthesis cultures; however, C14 movement between root systems artifically linked by mycelial strands indicated that interplant exchange can take place. Evidence suggests that mycorrhizal fungi such as T. terrestris could be effective in the exchange of organic and possibly other materials between root systems in an ecosystem.

The structure and function of the vegetative mycelium of ectomycorrhizal plants IV. Qualitative analysis of carbohydrate contents of mycelium interconnecting host plants.

“…Reciprocal transfer of carbohydrates between host and mycobiont has also been reported by several workers (Reid & Woods, 1969;Read, Francis & Finlay, 1985;Duddridge et al, 1988). The form in which carbohydrates occur in the fungal tissue will be important in determining the balance of this transfer and it is clearly of interest to determine which carbon compounds move from fungus to host.…”

Ectomycorrhizal mediation of competition between coniferous tree species

“…The fact that enhanced Psetidotsuga menziesii growth in n-iixture was due solely to L. laeeata -which formed mycorrhizas on both tree species -raises the possibility of nutrient transfers between plants through shared mycorrhizas. Various studies ha\'e provided strong evidence for such transfers (Reid & Woods, 1969;Read et al, 1985;Finlay & Read, 1986a, /;;Francis et al, 1986), and we did see cross inoculation -i.e. trees inoculated only with Rhizo.-pogon formed mycorrhizas with Laccaria and Heheloma.…”

DEVELOPMENT OF MYCORRHIZAE, EXTRAMATRICAL MYCELIUM AND SCLEROTIA ON PINUS STROBUS SEEDLINGS

“…Skinner and Bowen (1974a) demonstrated the role of hyphal strands in the translocation of ^^P from the soil solution to the ectomycorrhizal host plant. In the reverse direction, Reid and Woods (1969) showed that applying [^^C]glucose or [^^C]sucrose to the leaves of Pinus taeda L. resulted in detection of radioactivity in the hyphal strands of Thelephora terrestris (Ehrh.) Fr.…”