PALMYRAH PALM IN VITRO EMBRYO CULTURE AND HISTOLOGICAL ANALYSIS OF EMBRYONIC DEVELOPMENT IN CULTURE MEDIA

Abstract

Palmyrah palm (Borassus flabellifer) propagation relies solely on seeds due to the lack of vegetative methods. Seed germination, a slow hypogeal process forming a “cotyledonary tube” (apocolon), takes 5-6 months. This study presents the first attempt at in vitro culture of Palmyrah palm embryos with a histological analysis of their development. After 150 days, plumule emergence from the apocolon was observed in a limited number (2 out of 240) of cultured embryos. Half-strength Y3 medium yielded the fastest apocolon growth (88.33%), followed by half-strength MS medium (85%). However, shoot formation (3.33%) was observed only in half-strength Y3 medium. Histological analyses revealed an absence of clear differentiation in mature embryos during initial apocolon development. Higher magnification visualized meristematic centres within the embryonic axis, where cell division formed a proembryonal cell complex. As development progressed, the embryonic axis relocated towards the apocolon’s tip. Leaf primordia formation was observed within the germ tube’s posterior end after 120 days of incubation. These findings demonstrate the potential of in vitro culture for Palmyrah palm propagation, although further optimization is required to improve shoot development.