GENERATION PROCESS OF GROWTH STRESSES IN CELL-WALLS .6. ANALYSIS OF GROWTH STRESS GENERATION BY USING A CELL MODEL HAVING 3 LAYERS (S1, S2, AND I+P)

The propriety of the ''unified hypothesis'' is discussed quantitatively by using a newly improved cell model. The critical MFA; namely, microfibril angle where the longitudinal growth stress switches from contraction to expansion, becomes quite larger than the experimental one in the case of using a usual cell model. To solve the above discrepancy, we developed the usual cell model into a more realistic one with the outermost layer of the secondary wall (S1 layer); thereafter, we discuss the action of the S1 layer upon the dimensional changes of the cell model during the secondary wall lignification. From this analysis, we can explain the experimental phenomena more rationally by considering the action of the S1 layer. This suggests that the anisotropic growth stresses in cell walls are generated on the basis of the mechanism of the ''unified hypothesis'' during lignification not only in the middle layer of the secondary wall (S2 layer) but also in the S1 layer.