Marîa Félix Ramos-Ordoñez

Parthenocarpy and Seed Predation by Insects in Bursera morelensis

BACKGROUND AND AIMS While parthenocarpy (meaning the production of fruits without seeds) may limit fecundity in many plants, its function is not clear; it has been proposed, however, that it might be associated with a strategy to avoid seed predation. Bursera morelensis is a dioecious endemic plant that produces fruits with and without seeds, and its fruits are parasitized by insects. Its reproductive system is not well described and no published evidence of parthenocarpy exists for the species. The purpose of this work was to describe the breeding system of B. morelensis and its relationship to seed predation by insects. METHODS The breeding system was described using pollination experiments, verifying the presence of parthenocarpic fruits and apomictic seeds. Reproductive structures from flower buds to mature fruits were quantified. For fruits, an anatomical and histological characterization was made. The number of fruits in which seeds had been predated by insects was correlated with parthenocarpic fruit production. KEY RESULTS The major abortion of reproductive structures occurred during fruit set. The results discard the formation of apomictic seeds. Flowers that were not pollinated formed parthenocarpic fruits and these could be distinguished during early developmental stages. In parthenocarpic fruits in the first stages of development, an unusual spread of internal walls of the ovary occurred invading the locule and preventing ovule development. Unlike fruits with seeds, parthenocarpic fruits do not have calcium oxalate crystals in the ovary wall. Both fruit types can be separated in the field at fruit maturity by the presence of dehiscence, complete in seeded and partial in parthenocarpic fruits. Trees with more parthenocarpic fruits had more parasitized fruits. CONCLUSIONS This is the first time the anatomy of parthenocarpic fruits in Burseraceae has been described. Parthenocarpic fruits in B. morelensis might function as a deceit strategy for insect seed predators as they are unprotected both chemically and mechanically by the absence of calcium oxalate crystals.

The fruit of Bursera: structure, maturation and parthenocarpy

This study provides new information on fruit ripening of Bursera, from a structural and phenological point of view, we show some development patterns that must be taken into account in future physiological, ecological and management studies.

Parthenocarpy and Seed Production in Burseraceae

Seed production is determined by biotic and abiotic factors; however, crop viability can be affected negatively by phenomenon such as parthenocarpy (production of seedless fruits). Bursera morelensis is a deciduous species endemic to Mexico that occurs in the Tehuacan Valley and illustrates the strong effect of parthenocarpy. There is high annual variability in the production of fertilized and parthenocarpic fruits. In some years, crop yield is greater, and fruit removal and visits by birds are higher as compared to a year with poor crops. In mast years, parthenocarpy is a factor that helps to attract seed dispersers, which also reduces predation by insects and birds. These advantages of parthenocarpy probably cannot be observed in years with low fruit production but in years with large crops, this phenomenon can help maximize profits by increasing plant reproductive success.