CYTOCHEMICAL-LOCALIZATION OF ADENYLATE-CYCLASE ACTIVITY IN THE SYMBIOTIC PROTOCORMS OF SPIRANTHES SINENSIS

A cytochemical method has been used to investigate the localization of adenylate cyclase [EC 4.6.1.1] activity in the protocorms of Spiranth es sinensis developing with one of its endomycorrhizal fungi, Ceratoba sidium cornigerum and in seeds cultured without fungi. In both symbiot ic protocorms and asymbiotic seeds, the reaction products precipitated on the exterior side of the host plasma membrane in contact with the host cell wall. The invagination sites of the plasma membrane and vesi cles near the membrane showed a strong reaction. Non-electron-dense de posits were found on the host membrane enveloping the hyphae and on th e fungal plasma membrane. The host membrane enveloping the hyphae stai ned with the two selective stains for plasma membrane of plant cells, phosphotungstic acid-chromic acid and alkaline bismuth. The detection of the adenylate cyclase activity on the host plasma membrane in conta ct with host cell wall suggested the presence of cAMP in orchid tissue s, and the absence of activity on the host plasma membrane enveloping the hyphae suggested that cAMP played no role in the interface between host and fungus.