Specific patterns of cortical and endoplasmic microtubules associated with cell growth and tissue differentiation in roots of maize (Zea mays L.)

Indirect immunofluorescence using a-tubulin antibodies applied to sections of maize roots prepared using low melting point wax was found to give excellent visualisation of both cortical and endoplasmic microtubule (MT) arrays. This allows, for the first time, these arrays to be investigated in cells of the different tissues at various stages of their growth and development. Many cells in the zone between the mcristem and the cell elongation region develop a highly ordered transversal bundling of cortical MTs, which we suggest is related to vacuolation of the cytoplasm and which may also be indispensable for the ensuing rapid cell elongation. On the other hand, there are subtle differences between the cells of the individual tissues regarding the arrangement of thencortical MTs in this zone. The possible physiological significance of these tissue-specific MT arrays is discussed. Endoplasmic MTs were seen to encircle and to connect the nucleus with the cortical MT arrays in both dividing and elongating cells. Even the G, phase nuclei of the slowly dividing cells of the quiescent centre were encircled by endoplasmic MTs. The continuity of the two MT systems may provide the cell with an important signalling system whereby mechanical and physiological information is relayed from the exterior of the cell to the nucleus.