Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 341

Adventitious shoots originate from adventitious meristems. Non‐meristematic tissue can be induced to form plant organs (e.g. embryos, flowers, leaves, shoots, roots). Differentiated plant cells (with specific functional roles) can be induced to dedifferentiate from their current structural and functional state, and then embark upon a new developmental path to produce new structures. Adventitious shoot production through organogenesis occurs by one of two pathways – indirect or direct.

1 Indirect organogenesisThe indirect organogenetic pathway goes through a stage in which a mass of dedifferentiated cells (callus) forms (i.e. the explant forms a callus from which adventitious meristems are induced and from which plant regeneration is initiated). The callus consists of an aggregation of meristem‐like cells that are developmentally plastic (can be manipulated to redirect morphogenic end point). The negative side of this method is that the callus phase sometimes introduces mutations (somaclonal variation, making this not always a 100% clonal procedure). The callus phase also makes it more technically challenging than shoot tip micropropagation.

2 Direct organogenesisDirect organogenesis bypasses a callus stage in forming plant organs. The cells in the explant act as direct precursors of a new primordium. This pathway is less common than the callus mediated pathway.