PARENT SESSION
Poster Session #46: Seed Production, Recruitment, and Pollination.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Effect of pollen load and source on pistillate-phase duration, seed production, and floral developmental rate in Mimulus guttatus.

JOHNSTON , TAMMY ¹, ALGERS-GARCIA, JANICE¹, NAKAZATO, TAKUYA¹, ¹

ABSTRACT- Floral longevity is important for reproductive success, both through pollen deposition and dispersal. It varies greatly both among and within species and is affected by many factors. We examined the effect of pollen quantity (high versus low) and pollen quality (self versus outcross pollen) on duration of stigma receptivity and floral development rate in Mimulus guttatus. High pollen led to decreased duration of the pistillate-phase and increased seed number and mass regardless of pollen source (p<0.05 at 4 of 5 nodes). Planned comparisons showed that outcrossed flowers exhibited decreased duration of the pistillate phase and increased seed number and mass relative to selfed flowers only at high pollen loads. There was a negative relationship between the duration of the pistillate phase in an individual flower and the rate of flower production of the plant. Regardless of the treatment, maternal lines differed in length of stigma receptivity and floral development rate, suggesting that these traits are genetically based and may therefore be subject to selection. Results of this study indicate a possible trade-off between the benefit of acquiring more outcrossed pollen and the cost of lengthening pistillate phase, and are discussed in relation to increased opportunities for delayed selfing, geitonogamy, and pollen-pistil interference.

KEY WORDS: floral phenology, stigma receptivity, Mimulus guttatus