Amyloplasts as a possible indicator of morphogenic potential in sunflower protoplasts

Abstract

Sunflower plants (inbred line 47 302 bcd) can be regenerated from hypocotyl protoplasts. During the regeneration process, we have observed two kinds of calli differing by their cell types. Morphogenic calli, from which regeneration of shoots was possible, were characterized by the presence of starch granules, and clusters of small meristematic-like cells. Non-morphogenic calli did not contain either meristematic-like cells or starch, but a varying proportion of the typical callus cells at more or less advanced stages of degeneration. We have analyzed samples from each step of protoplast culture for the presence of starch, i.e. the initial protoplast population, micro- and macro-colonies and calli. On each step, only a small percentage of the structures contained starch. These results are discussed in view of a possible origin of these morphogenic calli from particular cell types existing in the donor tissue, i.e. stomatal guard cells and endodermis cells.