<P> The three common pathways of plant tissue culture regeneration are propagation from preexisting meristems (shoot culture or nodal culture), organogenesis and non-zygotic embryogenesis . </P> <P> The propagation of shoots or nodal segments is usually performed in four stages for mass production of plantlets through in vitro vegetative multiplication but organogenesis is a common method of micropropagation that involves tissue regeneration of adventitious organs or axillary buds directly or indirectly from the explants . Non-zygotic embryogenesis is a noteworthy developmental pathway that is highly comparable to that of zygotic embryos and it is an important pathway for producing somaclonal variants, developing artificial seeds, and synthesizing metabolites . Due to the single cell origin of non-zygotic embryos, they are preferred in several regeneration systems for micropropagation, ploidy manipulation, gene transfer, and synthetic seed production . Nonetheless, tissue regeneration via organogenesis has also proved to be advantageous for studying regulatory mechanisms of plant development . </P> <P> The tissue obtained from a plant to be cultured is called an explant . </P> <P> Explants can be taken from many different parts of a plant, including portions of shoots, leaves, stems, flowers, roots, single undifferentiated cells and from many types of mature cells provided are they still contain living cytoplasm and nuclei and are able de-differentiate and resume cell division . This has given rise to the concept of totipotentency of plant cells. (1) However this is not true for all cells or for all plants . In many species explants of various organs vary in their rates of growth and regeneration, while some do not grow at all . The choice of explant material also determines if the plantlets developed via tissue culture are haploid or diploid . Also the risk of microbial contamination is increased with inappropriate explants . </P>

Who started the technique of plant tissue culture