Organelles associated with the plasma membrane of tobacco leaf protoplasts.

Leaf protoplasts of tobacco (Nicotiana tabacum) heterozygous (Su/su) and normal (su/su) for the sulfur mutation exhibit a characteristic lag period before initiating cell wall formation. The early wall is composed of a network of Calcofluor positive fibrils. Large fragments of plasma membrane from freshly isolated protoplasts were examined by electron microscopy to determine the distribution of associated organelles. Coated vesicles and patches of coat material were present on the inner surface of the plasma membrane. The frequency of coated vesicles observed was considerably less than reported for protoplasts from suspension cultured tobacco cells. Very few microtubules were associated with the plasma membrane but fine filaments were frequently observed.