DEPENDENCE OF LACCARIA-BICOLOR-BASIDIOME DEVELOPMENT ON CURRENT PHOTOSYNTHESIS OF PINUS-STROBUS SEEDLINGS

Development of the Laccaria bicolor (Maire) Orton basidiome in associa tion with container-grown Pinus strobus L. seedlings was influenced by photosynthetic photon flux densities (PPFD). Three growth patterns we re observed. At a PPFD of 330 mu mol.m(-2). s(-1), basidiome growth wa s rapid, and complete development was achieved after 16 days. At a ver y low PPFD (20 mu mol.m(-2).s(-1)), the basidiome development ceased, although some residual growth was observed for a few days. At an inter mediate PPFD (50 and 90 mu mol.m(-2).s(-1)), basidiome growth was less rapid than that observed at 330 mu mol.m(-2).(s-1). Significant diffe rences in the net photosynthesis of the host plant resulted in corresp onding changes in basidiome biomass. The effect of basidiome removal o n the photosynthetic response of the host plant was evaluated at three stages of basidiome development (2- to 4-, 6- to 8-, and 10- to 15-mm pileus diameter). At each developmental stage, removal of the basidio me induced a very rapid decrease in both net photosynthesis and stomat al conductance of the host plant. This decrease in net photosynthesis indicates that the growth and development of the basidiome are depende nt on the host plant's current rate of net photosynthesis.