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Pollination biology of Theobroma and Herrania (Sterculiaceae)—I. Floral Biology

  • Allen M. Young (a1), Eric H. Erickson (a2), Melanie A. Strand (a3) and Barbara J. Erickson (a4)


Floral characteristics related to pollination were studied in four species of Theobroma and one species of Herrania (Sterculiaceae) in Costa Rica. Anthesis was complete in T. cacao, T. simiarum, T. speciosum, and T. mammosum at 0615 hr following an extended period of floral development throughout the night. Flowers of both T. cacao and Herrania cuatrecusana were fully open by dawn and pollen sacs dehisced throughout the morning hours. Stigma and style receptivity, assessed by hydrogen peroxide tests, were high throughout the morning and early afternoon in T. cacao. Bagged flowers resulted in no fruit-set. When petal ligules were experimentally removed there was no change in rates of flower abortion or total numbers of aborted flowers, tentatively suggesting that these structures play little or no role in attracting pollinators. Both Theobroma and Herrania flowers possess ultraviolet light reflectance'absorbance patterns which may play a role in pollinator attraction. Uptake of neutral red stain in T. cacao and T. simiarum showed scattered glandular activity on petals and sepals, perhaps indicating location of nectaries or other secretory organs. Conspicuous glandular trichomes on the ovary, on the lower third of the style, and in a conspicuous “basal ring” between petals and sepals (most pronounced and colorful in species other than T. cacao) may be sources of both floral attractant and reward.

Differences in floral biology among Theobroma and Herrania species suggest divergence in pollination strategies. The data presented are discussed in terms of plant-pollinator specializations in the New World tropics.

Les caractéristiques florales liées à la pollinisation ont été étudiées dans quatre espèces de Theobroma et une espèce de Herrania (Sterculiaceae) au Costa-Rica. L'anthèse était complète dans T. cacao, T. simiarum, T. speciosum et T. mammosum à 06.15 hr après une longue période de développement floral au cours de la nuit. Les fleurs de T. cacao et de Herrania étaient complètement déhiscentes à l'aube et les sacs de pollen se sont ouverts pendant toute la matinée. La réceptivité des stigmates et des styles mesurée par des tests d'hydrogène peroxyde était élevé pendant la matinée et en début de'après-midi pour T. cacao. Les fleurs ensachées n'ont pas produit de fruits. Quand les ligules des pétales ont été enlevées à titre d'expérience il ne s'est produit aucun changement dans le taux d'avortement ou le nombre total de fleurs avortées suggérant que ces structures n'influencent que peu ou pas l'attraction des polliniseurs. Les fleurs de Theobroma et de Herrania peuvent toutes deux réfléchir ou absorber la lumière ultraviolette, ce qui peut jouer un rôle dans l'attraction des polliniseurs. L'absorption de colorant rouge neutre a révélé une activité glandulaire diffuse des pétales et sépales, indiquant peut-etre la localisation de nectaires ou autres organes secréteurs. D'évidents trichomes glandularies sur l'ovaire à hauteur du tiers inférieur du style et un “anneau basel” bien visible entre les pétales et les sépales (très prononcés et colorés dans les espèces autres que T. cacao) sont peut-être les sources de l'attraction florale et de récompense nourricière. Les différences de biologie florale entre les espèces Theobroma et Herrania suggèrent des différences dans les stratégies de pollinisation. Les données présentées sont discutées en termes de spécialisations des polliniseurs de plantes dans les tropiques du Nouveau Monde.



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Pollination biology of Theobroma and Herrania (Sterculiaceae)—I. Floral Biology

  • Allen M. Young (a1), Eric H. Erickson (a2), Melanie A. Strand (a3) and Barbara J. Erickson (a4)


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