Propagation from Nonmeristematic Tissues-Organogenesis

Adventitious shoots and roots are the most common forms of adventitious organ formation.• Vegetative propagation via organogenesis is an important reproduction method used natu-• rally by plants. Certain plants have evolved unique alternative life cycles that use organogenesis rather than seed propagation to exploit unique habitats. Clonal propagation via organogenesis is also an important alternative to seed propagation•in agricultural, horticultural, and forestry production systems. Organogenesis in tissue culture can be exploited in novel ways for plant improvement•including the induction of somaclonal variation and as an important step in the induction and recovery of genetically transformed plants. Organogenesis progresses through dedifferentiation and redifferentiation phases. During•these phases, plant cells become competent to respond to inductive signals and determined for organ fate (i.e., an adventitious root or shoot). The ratio of auxin to cytokinin is the critical factor determining whether morphogenesis•will result in either an adventitious shoot or root in competent explants. In addition to hormone signals, tissue maturity of the explant donor can be critical to the•explant’s competency to respond to morphogenetic signals to form adventitious organs. In the modern age of bioinformatics, the most important model systems for studying•adventitious organ formation will have tissue that is easily genetically transformed, have available or easily induced mutations, and signicant genome sequence information.