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Plant Physiology 97:175-181 (1991) © 1991 American Society of Plant Biologists Microtubules in Mesophyll Cells of Nonacclimated and Cold-Acclimated Spinach 1Visualization and Responses to Freezing, Low Temperature, and DehydrationDepartment of Horticultural Science, University of Minnesota, St. Paul, Minnesota 55108, Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108
Responses of cortical microtubules in spinach (Spinacia oleracea L. cv Bloomsdale) mesophyll cells to freezing, thawing, supercooling, and dehydration were assessed. Microtubules were visualized using a modified procedure for indirect immunofluorescence microscopy. Leaf sections of nonacclimated and cold-acclimated spinach were slowly frozen to various temperatures, fixed while frozen, and microtubules immunolabelled. Both nonacclimated and cold-acclimated cells exhibited nearly complete microtubule depolymerization after ice formation. After 1 hour thawing at 23°C, microtubules in both nonacclimated and cold-acclimated cells repolymerized. With time, however, microtubules in nonacclimated cells again depolymerized. Since microtubules in cells of leaf tissue frozen slowly are subjected to dehydration as well as subzero temperatures, these stresses were applied separately and their effects on microtubules noted. Supercooling induced microtubule depolymerization in both nonacclimated and cold-acclimated cells, but to a smaller extent than did freezing. Exposing leaf sections to solutions of sorbitol (a cell wall-penetrating osmoticum) or polyethylene glycol 10,000 (a nonpenetrating osmoticum) at room temperature caused microtubule depolymerization. The effects of low temperature and dehydration are roughly additive in producing the observed microtubule responses during freezing. Only small differences in microtubule stability were resolved between nonacclimated and cold-acclimated cells.
2 Present address: Colorado Agricultural Experiment Station, Arkansas Valley Research Center, 27901 Rd 21, Rocky Ford, CO 81607. 1 Supported by the United States Department of Agriculture Grant 85-CRCR-1-1666. This paper is a contribution from the Minnesota Agricultural Experiment Station, Journal Article No. 18755. This article has been cited by other articles:
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