BESMER, YLVA1, ROGER KOIDE1.
Department of Horticulture, The Pennsylvania State University, University Park, PA 16802, USA.
Two varieties of snapdragons with different sensitivities to exogenous ethylene were used to investigate the effect of P and VA mycorrhizal colonization on growth, vase-life and ethylene production of the flowers. In the first experiment, nonmycorrhizal plants were grown in a soilless medium at 3 and 15 mg P mL-1 . In the second experiment, all plants were grown at 3 mg P mL-1 but half the plants were inoculated with Glomus intraradices while half were nonmycorrhizal. The mean percent colonization of the inoculated plants for the two varieties were 71 and 72 %. In the first experiment, 15 mg P mL-1 significantly decreased the number of days to flowering while it increased the total number of flowers on the spike, total plant fresh weight, and flower ethylene production. There was no significant effect on cut flower vase life. In the second experiment, mycorrhizal colonization did not significantly affect plant fresh weight or the total number of flowers on the spike but significantly decreased flower ethylene production and increased the vase life by one day. The results were the same for the two varieties but in both experiments the ethylene-insensitive variety produced significantly more ethylene and lasted about three fewer days in the vase than the sensitive variety, suggesting different controls on exogenous and endogenous ethylene. Since the high P treatment increased ethylene production and mycorrhizal colonization decreased it, mycorrhizal colonization may influence ethylene production in a way unrelated to P concentration. These results indicate that inoculation could be used to prolong vase life of some cut flowers and replace environmentally unfriendly ethylene inhibitors such as silver thiosulfate.