Preprophase microtubules and stomatal differentiation; some effects of centrifugation on symmetrical and asymmetrical cell division.

Abstract

Young wheat seedlings were centrifuged; premitotic and dividing cells of the leaf epidermis were examined. During the normal symmetrical, and also the first asymmetrical division (forming future guard mother cells), preprophase nuclei resisted sedimentation to a varying extent, dependent somewhat on the size of the preprophase band of microtubules. At other stages of these divisions, the spindle invariably sedimented, with accompanying structural disruption. During the second asymmetrical division (forming the subsidiary cell of the stomatal complex), all stages of division were highly polarized, and one pole remained adjacent to the GMC. Evidence is also presented which indicates that prepr..