Amyloplast formation in cultured tobacco cells; effects of plant hormones on multiplication, size, and starch content.

In BY-2 cultured tobacco cells (Nicotiana tabacum L.), depletion of 2,4-dichlorophenoxyacetic acid (2,4-D) and addition of benzyladenine (BA) caused amyloplast formation, a decrease in cell multiplication, and an increase in cell size. These changes were primarily triggered by the depletion of 2,4-D, and facilitated by the addition of BA. An increase in the starch content of BY-2 cells was always accompanied by a reduction in cell multiplication. However, when hormonal conditions were unsuitable for amyloplast formation, the starch content of the cells did not increase, even if cell multiplication was forcibly terminated by the addition of aphidicolin. This result indicates that the hormonal conditions themselves, and not the decrease in cell multiplication, induce amyloplast formation in BY-2 cultured tobacco cells.