Introduction

Pimento (Pimenta dioica) is an economically valuable tree yielding ‘allspice’, leaf and berry essential oils, an indispensable part of Caribbean and global cuisines. Under threat locally, this study of its floral biology identifies and confirms functional dioecy –male and female flowers borne on separate individual trees (which appear isophenotypical).

Methodology

Assessments of floral morphology and physiology from bearing (‘female’) and non-bearing (‘male’) trees were carried out on samples from sites around the island (figure 1).

Results

There were significant differences in size and number of floral parts:

• Male unilocular flowers were twice as large, bearing twice asmany stamens as bilocular female flowers, but 17% more flowers were in the female cluster.
• Pollen grains are aperturate yet pollen tubes from female flowers ruptured early in their germination (figures 2 and 3).
• Flowers were entomophilous (figure 4). Unbagged flowers set fruit completely while flowers isolated with bridal tulle and by plastic bags all aborted (figure 5).
• The annual flowering event of pimento progresses west to east, initiated by confluent increases in rainfall, temperature and daylength (figure 6).

Conclusion

Pimento flowers are definitely insect-pollinated. Differential allocation of reproductive resource is operative for the maximization of male function in pollen delivery and optimization of female function in berry-bearing. Rupture of female pollen tubes reveals one aspect of the cryptic dioecy inherent in the reproductive biology of this plant.

Relevance and Potential Application

Investigation provides for the development of orchard cropping to increase the quantity and qualityof this commodity which of great significance to the local economy