Counting chloroplasts (
proplastids) in meristematic cells of shoot tips or root tips is cumbersome, requires serial cuttings for electron microscopy, and has been carried out so far in only about six species of spermatophytes (references in Butterfass, 1979; Cel'niker & Maj, 1979).
Before meiosis, all of the anther cells have
proplastids, and in some cases they may accumulate starch.
Plastid nucleoid structure and protein composition vary during the development of
proplastids to chloroplasts, suggesting that genome packaging may play a crucial role in the regulation of replication, transcription, and recombination.
The streaks may be a result of the loss of chloroplasts or by dedifferentiation of chloroplasts to smaller, colorless
proplastids (Kirk and Tilney-Bassett, 1978).