ADVENTITIOUS ROOT FORMATION AND ASSOCIATED BIOCHEMICAL CHANGES IN MICRO SHOOTS OF TECTONA GRANDIS CLONES

Globally, Tectona grandis (teak) is mass-produced through tissue culture. Being a perennial species, an understanding of adventitious rooting would significantly increase its production. This study investigated biochemical and histological changes and media compaction associated with rooting in eight tissue-cultured T. grandis clones. Root emergence was observed from the 3rd to 8th day in 4–5 cm long shoots treated with 5 mM indole-3-butyric acid (IBA). Root primordia became visible after 3 days in good rooters while root initiation, elongation and root emergence occurred between the 3rd and 7th day depending on the clone. Grade 5 vermiculite facilitated root formation and improved primary and secondary root thickness and length. Sugars and proteins increased during root initiation from day 1 to 3, reflecting active cell division using available energy sources. An initial low, followed by increased indole-3-acetic acid (IAA) levels revealed inhibition of endogenous auxin due to external supply, replaced later by the shoot’s auxin. The polyphenol oxidase (PPO) and indole-3-acetic acid oxidase (IAAO) levels increased during rhizogenesis. Therefore, it is clear that sugars, enzymes and proteins play a significant role during various rooting phases. The findings indicated the influence of biochemical pool composition on root system architecture. Genotype variation demands clone-specific protocols for successful commercial propagation of the species.