Structure of Nucleoli in Higher Plants by Scanning Electron Microscopy

Nucleoli of several species of higher plants were observed with a scanning electron microscope by the method of direct freeze-fracture and thaw-fixation. The general appearance of the nucleolus is similar in all species examined. On the surface of the nucleolus, there are many tiny pores 0.1-0.3 fan in diameter, which penetrate deeply into the organelle as narrow canals 0.1-0.3 fim in width. Based on minor differences among species, nucleoli in higher plants are classified into 3 types. (1) Compact type (Pisum and Vicia). The pores on the surface of the organelle do not penetrate deeply and there are only a few canals inside. (2) Canaliculated type (Zea, Kaphanus, Mirabilis, Cucurbita, Tradtscantia and Allium). Pores on the surface of the organelle penetrate deeply and form a complicated canal system in the organelle. (3) Nucleolonema type (Helianthus). Contorted filamentous structures, instead of canals, are conspicuous in this type. © 1985 Oxford University Press. All rights reserved.