Patterns of organ development in plant tissue culture and the problem of organ determination

Abstract

There is a need in plant development for greater understanding of the early determinative events in organ developmentin vitro. Two interest groups, one practically oriented and the other theoretically, are served by techniques for initiating new organsin vitro. A survey of morphogenic systems in use shows that there are a variety of routes leading to organ production. In general, a common pattern is for an intermediate callus to precede organogenesis. Because they did not involve this undesirable feature, two organogenic systems were considered in detail. One promising technique involves the use of cell layers as inocula. From these, rapid vigorous organogenesis occurs in a defined time period. Up to four different developmental sequences can be elicited from one tissue, by hormone manipulation. Biochemical events in determination in this system remain to be clarified. In another system, organ development from whole cultured meristems ofOpuntia could be chanelled into spine leaf or root development. Careful analytical study suggested that organ determination was specified directly in the meristem. The continued use of these techniques is encouraged, especially the further development of cell layer, meristem, and primordial organ methods in relation to questions of determination. Some anticipated difficulties were briefly discussed.