Reproduction of, and ultrastructural changes induced by,Spiroplasma citri in sieve tube of citrus leaves

摘要: Electron microscope examination of ultrathin sections leaf veins “stubborn”—affected citrus seedlings revealed three morphotypes ofSpiroplasma citri free in the cytoplasm mature sieve elements. In addition to these, inclusions believed beSpiroplasma citri, some various stages degeneration, were occasionally found inside spherical, ovoid, or angular membraneous structures (= packets) which occurred elements devoid any recognizable organelles. These packets varied size from 1.0 1.8 μm wide an 1.9 3.5 long bounded by unit membrane ca. 9 10 nm thick. Spiroplasmas and apparently absent healthy seedlings. Three types recognized based on spiroplasmas contained: type I contained large, intermediate, small spiroplasmas, but forms predominated; II a mixture large intermediate forms, while III essentially tightly—packed forms. Results study suggested that spiroplasma-containing are either definite reproductive peculiar toSpiroplasma sieve-tube cells plasmolysis. Evidence is presented indicating within given packet produced process cell constriction followed fission, budding. Since these spiroplasma—containing infrequently observed infected tissues we suggest division budding, fission into unequal daughter may be principal mode reproduction inSpiroplasma citri.