Pericarp development and fruit structure in borassoid palms (Arecaceae-Coryphoideae-Borasseae)

Area of Science:

• Botany
• Plant Anatomy
• Carpology

Background:

• The Borasseae tribe forms a distinct monophyletic group within the Arecaceae-Coryphoideae family.
• Coryphoideae fruits are typically small and drupaceous, with unique pericarp structures.
• Borassoid palms are characterized by large fruits containing massive pyrenes derived from the mesocarp.

Purpose of the Study:

• To describe the pericarp development process in borassoid palms.
• To identify diagnostic fruit features specific to the Borasseae tribe.
• To determine the morphogenetic fruit type within Borasseae genera.
• To compare fruit structure and pericarp development with other palm groups.

Main Methods:

• Developmental carpological study of fruits from all eight Borasseae genera.
• Analysis of pericarp anatomy using light microscopy on anatomical sections.

Main Results:

• Pericarp differentiation begins early in development.
• The mesocarp is multilayered, featuring peripheral and inner parenchymatous zones surrounding a stony pyrene.
• The stony pyrene develops from the middle mesocarp zone and contains sclereids and vascular bundles.
• The endocarp is not involved in pyrene formation, and the spermoderm varies between subtribes.

Conclusions:

• Borasseae fruits are classified as Latania-type pyrenaria.
• This specific pericarp differentiation is also observed in Eugeissona and Nypa.
• The fruits of other Coryphoideae exhibit significantly different anatomical structures and developmental patterns compared to Borasseae.