Interaction between the pollen tube and transmitting tract of Allamanda cathartica (Apocynaceae)

• Grant number: 23/05893-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2023
• End date: July 31, 2024
• Field of knowledge: Biological Sciences - Botany - Plant Morphology
• Principal Investigator: Diego Demarco
• Grantee: Amarylis Lins Torres
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Apocynaceae is a diverse family, with the highest degree of floral synorganization of the eudicotyledons. The various unions between organs of the same whorl and between different whorls gave rise to a complex morphology that is also reflected in an elaborate pollination system. These characteristics of the flowers of the family are linked, in large part, to a varied set of secretory tissues, which provide the attraction of pollinators, deposition of pollen on the stigma and direct the pollen tubes through the gynoecium to the micropyle of the ovules. Although the structure of the transmitting tissues is known, there are no data on how the interaction between the apex of the pollen tubes and the cells of this tissue along the gynoecium occurs. The objective of this study is to determine how substance exchange occurs between the pollen tube apex and the stylar transmitting tissue in Allamanda cathartica, investigating the factors involved in its nutrition and guidance. For this purpose, pre-anthetic flowers were cross-pollinated and the time for locating the tube apices in the intermediate region of the style was determined as 6h. The styles of the pollinated flowers were isolated and fixed for observation under light and transmission electron microscopy. Structural and histochemical analysis will be performed to investigate the characteristics of the stylar transmitting tissue and ultrastructural analysis will be used to verify interaction between the pollen tubes and carpel tissue. With these analyses, we hope to identify key factors in the interaction between the gametophytic structure and sporophytic tissues in A. cathartica that may be related to the reproductive success of the family.