Effects of Position and Plant Growth Regulators on Morphogenesis and Growth Rate of Coconut Endosperm In Vitro

Abstract

Endosperm position (antipodal and micropylar) and plant growth regulators were investigated for their effect on morphogenesis and the growth rate of coconut endosperm cultured in vitro. This experiment was conducted at the Tissue Culture Laboratory, Horticulture Department, University of Hawaii at Manoa, USA. Embryo companion and plant growth regulators were not necessary to induce callogenesis. Coconut endosperm explants started to form callus after 3 wk of culture. Callogenesis occurred in 98.83% of all treatments on 31 wk of culture. Endosperm positions and plant growth regulators did not affect signifi cantly the growth rate of the endosperm culture. The concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4- mino-3,5,6-trichloropicolinic acid (picloram) at 1 × 10^-3 M affected signifi cantly the growth rate after 9 wk of culture but did not inhibit thereafter. The growth rate of the control was the quickest on 31 wk of culture. Addition of 6-benzylaminopurine (BAP) did not affect signifi cantly the growth rate of the endosperm culture. The growth rate of tissues increased substantially but decreased on 31 wk of culture. Embryo-like structures appeared from antipodal position calli treated with 1 × 10^-6 M picloram. This study has provided the fi rst report of embryo-like structures occurring on coconut endosperm cultured in vitro.