PHOSPHORUS AND CARBON BUDGETS - MYCORRHIZAL CONTRIBUTION IN HYACINTHOIDES NON-SCRIPTA (L) CHOUARD EX ROTHM UNDER NATURAL CONDITIONS

The extent of host benefit from arbuscular mycorrhiza (AM) in terms of phosphorus (P) assimilation under natural conditions has rarely been demonstrated or quantified. An apparently obligately mycorrhizal host, Hyacinthoides non-scripta (L.) Chouard ex Rothm., was selected and, throughout the season September-July 1989-90, entire clones were collected from a field site at frequent intervals without experimental modification of the host, its mycosymbiont or their environment. in a concurrent glasshouse experiment, sand-cultured non-mycorrhizal plants given a nutrient solution containing a supply of P were unable to assimilate sufficient to maintain tissue P content. We provide correlative evidence of mycorrhizal behaviour in an undisturbed, natural ecosystem by demonstrating the temporal coincidence of root colonization by mycorrhizal fungi and the inflow of phosphorus in adult H. non-scripta. Annual carbon (biomass) and phosphorus budgets are described. Carbon was reallocated from the resting bulb, first for root production and, later, to developing leaves and inflorescences. A similar pattern was observed in P allocation. A substantial amount of P was lost in seed, leaves, roots and scapes shed at the end of a season, when bulb biomass had increased, but P content had not.