Elastic properties of the growth-controlling outer cell walls of maize coleoptile epidermis
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The effects of tensile stress and temperature on cell wall elasticity have been investigated in the outer cell walls of coleoptile epidermis of 4- and 6-day-old Zea mays L. seedlings. The change in tensile stress from 6 to 40 MPa caused the increase in cell wall elastic modulus from 0.4 to 3 GPa. Lowering the temperature from 30 to 4 °C resulted in instantaneous and reversible cell wall elongation of 0.3–0.5 ‰. At a given temperature and stress level, the wall elastic modulus of 6-day-old seedlings tended to be 30 % higher than that of 4-day-old plants. The relationship between cell wall elasticity and mechanical stress indicated that the stress distribution within the cell wall is highly uneven. The analysis of the effect of temperature on cell wall elastic strain showed that structural differences between crystalline and amorphous load-bearing polymers were not the only cause of the uneven stress distribution. Based on the results obtained by Hejnowicz and Borowska-Wykręt (Planta 220:465–473, 2005), we suggested that the uneven stress distribution is partially related to the stress gradient between inner and outer layers of the cell wall.
KeywordsZea mays Plant cell wall Epidermis Modulus of elasticity Extension growth
We gratefully acknowledge Professor Svetlana M. Bauer for valuable discussions. We are immensely indebted to Alexandra N. Ivanova, Kirill N. Demchenko and Pavel A. Zykin for assistance with the microscopic investigations. We thank anonymous reviewers for their comments, which greatly helped to improve the manuscript. The work was partially carried out at the Core Facilities “Molecular and Cell Technologies” (SPbSU) and “Cell and Molecular Technologies in Plant Science” (Komarov Botanical Institute RAS, St.-Petersburg). This work was supported by Russian Foundation for Basic Research (Grant No. 11-04-00701).
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