Pollination and Reproductive Biology of Rauvolfia grandiflora (Apocynaceae): Secondary Pollen Presentation, Herkogamy and Self-Incompatibility

Abstract

The pollination and reproductive biology of Rauvolfia grandiflora were studied in natural populations in the forest of the Recife Botanical Garden. R. grandiflora is a shrubby species (2 to 5 m), the flowers are hermaphrodite and salverform. The corolla tube is white and the five free lobes of the corolla are flushed with violet. The five stamens are attached to the corolla tube; the anthers are introrse and form a cone situated immediately above the stigmatic head. There is a space between the anthers and the stigmatic head, where the pollen is deposited. The stigmatic head has three functional regions: a) an upper sterile region; b) a median region that produces a sticky substance and c) a lower receptive region, which is located beneath a basal collar. The secondary pollen presentation and the herkogamy mechanisms are discussed. Sugar concentration in nectar was, on average, 31.7%. The pollen viability was 97.4%. R. grandiflora is melittophilous and in the study area was found to be pollinated by only one species of long-tongued bee, Exaerete smaragdina. R. grandiflora was found to be self-incompatible, and the percentage of fruit set under natural conditions was low.

Key words

Apocynaceae - Rauvolfia - melittophily - secondary pollen presentation - herkogamy - self-incompatibility