Floral longevity and scent respond to pollen manipulation and resource status in the tropical orchid Myrmecophila christinae

Abstract

Floral longevity (FL) is a key aspect in plant reproductive ecology. Despite this, the effect of resource status on FL has usually been ignored, and never has resource status been linked to the effects of pollen manipulation on FL. In addition, immediate changes in floral scent characteristics subsequent to pollen addition/removal have not been looked at. Here we use the tropical orchid Myrmecophila christinae to address the following: (1) Does flower bud removal (resource status change) increase FL? (2) Does pollen manipulation (addition/removal) decrease FL, and do such effects interact with plant resource status? (3) Are there rapid changes in floral scent production and composition after pollen manipulation? To answer the first question, we removed 50% of the flower buds on 24 plants (24 more were controls). To test the second question, 1 month after removing buds, one of four flowers on each inflorescence received one of the following treatments: no manipulation, pollinia removal, pollination, or pollination + pollinia removal. Finally, to answer the third question, one of four flowers on each of 15 plants (different site) received one of the above-mentioned pollen treatments. Flowers were collected 2, 4, and 6 h after manipulation to measure scent production/composition. Results showed that flowers on bud-removed plants remained open significantly longer relative to those on control plants, and that pollination significantly decreased FL. Additionally, scent production increased throughout the morning and responded differently depending on the pollen manipulation treatment; scent composition on the other hand, remained relatively unchanged throughout the sampling period. By studying both floral scent and physical changes in M. christinae, this study intends to offer a more integrated view of floral senescence within the context of resource and pollen status conditions.