The relationship between the endoplasmic reticulum and microtubular aggregation and disaggregation

Summary During mitosis groups of microtubules appear consecutively at three different sites in dividing plant cells. They are found at the pre-prophase band encircling the nucleus, at the mitotic poles from which they radiate into the spindle, and at the edge of the cell plate during its development. In the meristematic cells of wheat root-tips it is possible to synchronize the cell divisions by the use of 5-amino-uracil and to layer the organelles of the cells by gentle centrifugation of the whole root. These techniques make it possible to investigate the cell sites at which the microtubules arise during their formation and to see the particular organelles which occur at these sites together with the microtubules. From this type of study it is suggested that profiles of smooth endoplasmic reticulum are concerned with the processes of transport and aggregation of the microtubular sub-units.