Coconut Inflorescence Sap: Novel Supplement for Enhancing Somatic Embryogenesis from Immature Inflorescence of Coconut (Cocos nucifera)

Abstract

Coconut exhibits recalcitrance to invitro regeneration due to its distinct morphological, anatomical, and physiological characteristics. Explant type and culture media composition are major factors influences embryogenic callus and somatic embryo induction. Immature inflorescence explants show greater responsiveness for somatic embryogenesis compared to plumule explants, which are less vegetative and represent a single embryo. Studies showed undefined organic additives could enhance invitro responses by promoting morphogenesis. Hence this study evaluated the effect of unfermented coconut inflorescence sap (CIS) on somatic embryogenesis from immature inflorescence explants invitro. Explants at various developmental stages were cultured on a standardized callus induction medium supplemented with CIS alone or combined with phytohormones. Explants at stages i3 (5–10 cm) and i4 (0–5 cm) exhibited superior morphogenic response and reduced browning with 10 ml L⁻¹ CIS. Among treatments, a medium containing 5.38 \(\mu\)M NAA, 4.5 \(\mu\)M TDZ, 66 \(\mu\)M 2,4-D, and 10 ml L⁻¹ CIS yielded the highest embryogenic callus induction (80.79%), while somatic embryo maturation peaked (72.93%) in medium with 4.54 μM 2,4-D, 20 μM BA, and 10 ml L⁻¹ CIS. These findings highlight CIS as a beneficial additive for improved somatic embryogenesis in coconut tissue culture.