Occurrence of a Putative Precursor to the Amyloplast, the “Amyloplast Initial” in Developing Stolons of the Potato

The proliferation of amyloplasts in meristematic cells of developing stolons of potato and apple callus: Progenitors of proplastids

“…They were slender and still small; in some cases they were 5-7 mm in length and 0.3-0.6 mm in width ( Figure 5; see also Sagisaka and Akita, 1994). Their characteristic features were elongation and subsequent constriction at random sites, with resultant increases in number (Figures 5 and 6).…”

“…In meristematic tissues (Marinos, 1967;Possingham, 1980;Possingham and Lawrence, 1983;Sagisaka and Akita, 1994) and developing pollen grains (Ameele, 1982;Nepi et al, 1996;Pacini et al, 1992), cells are rich in proplastids (formed via the A pathway) that are heterogeneous in terms of ultrastructure and metabolic activity (Akita and Sagisaka, 1995). These proplastids can be divided in terms of their development into younger ones (y proplastids) and older ones (o proplastids) (Akita and Sagisaka, 1995;Sagisaka et al, 1999).…”

“…Both y and o proplastids are visible. Some of them reached about 5-7 mm(Sagisaka and Akita, 1994) in length but are less than 1 mm in width, resulting in a narrow and slender form. The y and o proplastids contain neither thylakoid membranes nor starch granules*.…”