Morphological identification and characterization of the formation of floral primordium in Vanilla planifolia (Orchidaceae)

Abstract

ABSTRACT

Objective: To study the formation of floral primordia and individual flower development in the inflorescence of vanilla (Vanilla planifolia Jacks Ex. Andrews).

Design/methodology/approach: The study site was located at Rancho Xanathtlan, in Barriles, municipality of Gutiérrez Zamora, Veracruz. Inflorescence primordia and young inflorescences (racemes) at different stages of development were sampled from three different stem positions: basal (11-15 internodes), middle (6-10 internodes) and distal (1-5 internodes). Four samplings were made from February to May, and five replicates of each stem position were used per sampling date. Observations and characterization were carried out with a stereo microscope.

Results: Seven developmental stages were described for the racemes of V. planifolia: (I) differentiated meristem of the floral inflorescence, (II) appearance of the third bract, (III) initiation of the formation of the racemes, (IV) elongation of the floral primordia, (V) development and growth of the individual floral primordia in the acropetal direction, (VI) anthesis of the inflorescence in the acropetal direction and (VII) complete flowering of the raceme. Five developmental stages of formation of individual flower primordia within the inflorescence were also identified, which occurred from the appearance of the third bract in the acropetal direction.

Limitations on study/implications: Although this study denotes the first observations on the floral phenology of V. planifolia, there are still many questions about the biochemical processes and the interaction of environmental aspects in this floral development.

Findings/conclusions: First aspects of floral formation within the inflorescence as well as floral phenology in Vanilla planifolia were shown.

Keywords: Floral growth, floral phenology, inflorescences, orchids.