Physiological and fitness response of flowers to temperature and water augmentation in a high Andean geophyte.

Flowers are likely to be under various selective pressures not limited to reproduction and resource trade-offs. Here, we investigate the physiological responses (conductance, transpiration and respiration) of flowers under augmented temperature and supplemental watering, link these responses to actual flower longevity, and search for evidence of adaptive plasticity. Flower maintenance costs and plant fitness were investigated using the Andean geophyte, Rhodolirium montanum , in a manipulative field experiment. Maintenance determined by gas exchange was measured on fully expanded tepals; along with flower duration and its components, opening and closing. Fitness measured by fruit and seed production and seed set (mature/total) was examined. We artificially increased temperature and supplementally watered plants. Our study showed that flower longevity decreased under drier conditions, but the effect on flower opening and closing was even stronger, both of which advanced under higher temperatures without supplemental watering. Gas exchange also decreased, limiting water loss, under drier, warmer conditions. Those plants that reduced flower longevity under warming had higher total seed production and seed set. Plants that reduced conductance under warmed conditions also had higher seed set. These results suggest that plants are plastically optimizing fitness by reducing flower maintenance costs. Possible flower longevity and fitness connotations of our results under climate change are discussed. [ABSTRACT FROM AUTHOR]