Abstract

We developed a method to measure mechanical properties of single fibers of callose in liquid protoplast cultures of Larix leptolepis and Betula platyphylla, which were formed in media containing 50 mM of MgCl₂ or 100 mM of CaCl₂, respectively. Tensile test was performed using two micromanipulators loading micropipettes under an inverted microscope. Spring constant of the pipette used was first calibrated and calculated from using a microbalance. The callose fiber was wired between the two micropipettes. The Young’s modulus of single fibers for Larix and Betula was 7-9 kPa (1.4-1.9 x 10⁴ N/m²) though the diameters of the fiber varied from 10 μm for Larix and 22-26 μm for Betula. No difference was found between experiments with and without medium containing high concentrations of salts. Tensile strength at break was 1.1-1.8 kPa (2.3-3.6 x 10³ N/m²). The values are compared to other materials including cellulose containing plant cell wall, cell membranes, and amorphous callose. The value of the Young’s modulus observed was discussed.

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