Structure of the stigma and style of Callaeum psilophyllum (Malpighiaceae) and its relation with potential pollinators

ALISCIONI S.; GOTELLI M.; TORRETTA J.P.

PROTOPLASMA

SPRINGER WIEN

Lugar: Viena; Año: 2018

0033-183X

The family Malpighiaceae, particularly in the Neotropic, shows asimilar floral morphology. Although floral attraction and rewards topollinators are alike, stigmas and styles show more diversity. Thestigmas were described covered with a thin and impermeablecuticle that needs to be ruptured by the mechanical action of thepollinators. However, this characteristic was only mentioned for afew species and the anatomy and ultrastructure of the stigmas werenot explored. In this work, we analyze the morphology, anatomy,and ultrastructure of the stigma and style of Callaeum psilophyllum.Moreover, we identify the potential pollinators in order to evaluatehow the disposition of the stigmas is related with their size and itsrole in the exposure of the receptive stigmatic surface. Ourobservations indicate that Centris flavifrons, C. fuscata, C. tarsata,and C. trigonoides are probably efficient pollinators of C.psilophyllum. The three stigmas are covered by a cuticle thatremained intact in bagged flowers. The flowers exposed to visitorsshow the cuticle broken, more secretion in the intercellular spacesbetween sub-stigmatic cells and abundant electron-densecomponents inside vacuoles in stigmatic papillae. This indicatesthat the stigmas prepares in similar ways to receive pollen grains,but the pollinator action is required to break the cuticle, and oncepollen tubes start growing, stigmatic and sub-stigmatic cells releasemore secretion by a granulocrine process.