ULTRASTRUCTURAL CHANGES OF CHLOROPLASTS IN ATTACHED AND DETACHED, AGING PRIMARY WHEAT LEAVES

摘要: Degradation of chloroplasts is shown in mesophyll cells primary leaves wheat. The sequence ultrastructural changes naturally senescing compared with that detached, aging leaves. In leaves, the first indications are appearance osmiophilic globuli and reorientation thylakoidal system. membranes grana intergrana lamellae then become distended later dissociate into distinct vesicles. Concurrent these membrane changes, increase size number, stroma breaks down. Finally, chloroplast envelope ruptures plastid contents disperse throughout cell's interior. initial also include globuli, but stages degradation different. before break Swelling not pronounced and, additionally, system degenerates without forming vesicles or numerous globuli. These differences indicate rather than should be used studies senescence. THE SEQUENCE during leaf senescence varies among plant species, symptoms usually expressed (Butler Simon, 1971). Large within most conspicuous indicator Other ultrastructure loss starch grains, disappearance ribosomes, dilation thylakoids, (Barton, 1966; Colquhoun et al., 1975; Dodge, 1970; Haber 1969; Hernandez-Gil Schaedle, 1973; Ikeda Ueda, 1964; Mlodzianowski Kwintkiewicz, Ponitka, Roux McHale, 1968; Shaw Manocha, 1965). Attached allowed to senesce (Dodge, Freeman Duysen, Harris Arnott, Hurkman Kennedy, Ljubesic, Yoshida, 1961) detached discs (Dennis, Stubbs, Coulate, 1965) 1 Received for publication 14 June 1978; revision accepted 11 September 1978. I thank Mrs. Marilyn Schaller laboratory facilities Dr. G. S. Kennedy helpful discussions financial assistance. acknowledge Charles E. Bracker critically reading manuscript. 2Present address: Department Botany Plant Pathology, Purdue University, West Lafayette, Indiana 47907. have been Few those (Colquhoun Mittelheuser Van Steveninck, Such necessary determine if accurately represent This study examines both wheat MATERIALS AND METHODS-Wheat seeds, Triticum aestivum L. em. Thell. 'Chris' (Olds Seed Co., Madison WI) were surface-sterilized 5% Clorox, soaked overnight, sown trays containing moist vermiculite, grown a growth chamber (12 hr light at 800 ft-c 23 C-12 dark 17 C, 80% relative humidity). Detached, obtained by removal from plants on 10th day after sowing. ends recut under water, lots 10 placed 2.5 x 30 cm test tubes 2 ml water. kept water was changed daily. Naturally aging, 21 days. For electron microscopy, sections tissue taken mid-lamellar regions pri-