Extranuclear temperature-sensitive lethality in Nicotiana tabacum L. was investigated at the ultrastructural level. Chloroplasts of temperature-sensitive and control plants were morphologically similar in plants grown at nonlethal temperatures (26 C day/20 C night); both possessed typical lamellar structure, starch grains, and plastoglobuli. At lowered temperatures (13 C day/8 C night), chloroplasts in temperature-sensitive plants gradually degenerated as evidenced by the disappearance of starch, increase in plastoglobuli, and the formation of numerous vesicles from the dilation of thylakoids. Chloroplasts in control plants continued to accumulate starch in several large grains, occupying most of the plastid volume by the end of the investigation. Mitochondria in both temperature-sensitive and control plants were morphologically unaltered by exposure to lowered temperatures. Ultrastructural evidence suggests that the site of inheritance of extranuclear temperature-sensitive lethality in the mutant is in the chloroplast.
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Nessler et al. (1980) studied this question.