Roles of microtubules and microfibrils in growth and differentiation of plants.

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It is known that cortical microtubules (MTs) and wall microfibrils (MFs) play important roles in the regulation of growth and differentiation of unicellular plants. However, in multi-cellular plants, which have much more complex organization, involvement of cortical MTs and wall MFs in the regulation of growth and differentiation is not clearly revealed.The present study aimed observation of the overall arrangement of cortical MTs and wall MFs throughout tissues in organs of higher plants, such as shoot apices, stems and leaves, in relation to growth and differentiation of organs. The main results obtained are followings. 1.An improvement of immunofluorescence microscopy which made possible to examine the arrangement of cortical MTs throughout organs was established. 2.Arrangements of MTs and MFs are different between the tissues of the shoot apex, corresponding to formation and maintenance of the dome-like shape of the apex and tunics-corpus structure. 3.In elongating coleoptiles of Avena, epidermis and the inner tissue have the opposite mechanical properties each other. The arrangements of MTs and MFs are different between the epidermis and the inner tissues, corresponding to these mechanical properties. 4.Arrangements of MTs and MFs are different between epidermis and parenchyma cells of leaves. The paradermal view of arrangements of MTs and MFs in epidermal cells are different between monocotyledonous and dicotyledonous plants, corresponding to the growth patterns of leaf surface.In conclusion, these results demonstrate that much attention should be paid to the cytological differences between tissues of organs and that MTs and MFs may be involved universally in the regulation of growth pattern of organs in higher plants.