Relationship between the self-incompatibility and cAMP level in Lilium longiflorum

The elongation of pollen tubes in Lilium longiflorum cv. Hinomoto after sel f-incompatible pollination stopped halfway, but that after cross-compatible pollination (cross with cv. Georgia) did not. The elongation of pollen tub es after self-pollination was enhanced by exogenous CAMP and by pertussis t oxin or cholera toxin, which activates adenylate cyclase. The level of endo genous CAMP in pistils after self-pollination was approximately one half of that after cross-pollination. Furthermore, the activity of adenylate cycla se in pistils after self-pollination was also approximately one half of tha t after cross-pollination. By contrast, CAMP phosphodiesterase in pistils a fter self-pollination was approximately 2 times as high as that after cross -pollination. A possible correlation between self-incompatibility and the l ow level of endogenous cAMP in lily pistils is discussed on the basis of th ese results.