Effect of mycorrhizal colonization and phosphorus on ethylene production by snapdragon (Antirrhinum majus L.) flowers

We determined the effects of phosphorus (P) concentration and mycorrhizal c olonization on ethylene production by flowers of snapdragons (Antirrhinum m ajus L.). Mycorrhizal colonization in a soil-less medium did not significan tly affect the total number of flowers per spike or flower P concentration, but it significantly increased flower vase-life and significantly decrease d flower ethylene production. This demonstrates for the first time that myc orrhizal colonization can have a non-localized effect on host ethylene prod uction. The reduction in ethylene production caused by mycorrhizal coloniza tion was as large as the variation in ethylene production among snapdragon cultivars, Thus, mycorrhizal colonization may be a viable alternative to to xic ethylene inhibitors such as silver thiosulfate. Increased fertilizer P concentration (15 versus 3 mu g P ml(-1)) significantly increased plant fre sh weight and the total number of flowers per spike. In contrast to mycorrh izal colonization, increased fertilizer P concentration resulted in an incr ease in ethylene production. There was no significant effect of fertilizer P concentration on vase-life. This suggests that factors other than ethylen e have at least partial control over vase-life, Postharvest amendment of in dividual flowers with phosphate also significantly increased flower ethylen e production. Phosphorus apparently does not mediate the mycorrhizal effect because mycorrhizal colonization decreased ethylene production without sig nificantly influencing flower P concentration. Moreover, treatment with pho sphate increased flower ethylene production. Mycorrhizal colonization did n ot significantly influence response to exogenous ethylene.