Pre-prophase Microtubule Band and Local Wall Thickening in Guard Cell Mother Cells of Some Leguminosae

Abstract

An examination of leaf protodermal cells from 20 species belonging to the family Leguminosae (15 Lotoideae, three Mimosoideae and two Caesalpinioideae) revealed: (a) the organization of pre-prophase microtubule bands (PMBs), and (b) that the regions of the anticlinal walls of the guard cell mother cells (GMCs) lined by the PMB become detectably thickened. These local thickenings are deposited during the presence of pre-prophase microtubules which persist up to late prophase. During deposition of the thickenings the GMCs exhibit a significant dictyosome and endoplasmic reticulum (ER) activity. Smooth as well as coated dictyosome vesicles seem to fuse preferentially with the plasmalemma of the PMB cortical zone. The cell plate of the symmetrical division of the GMC meets the parental walls at the middle of the thickenings with surprising accuracy. It intersects the middle of the cortical cytoplasmic region traversed previously by the PMB. The observations favour the view that: (a) the deposition of the local wall thickenings in the cortical site of the plane of the future cytokinesis in GMCs must be a general feature of the Leguminosae, (b) in these plants the guard cell wall differentiation commences in GMCs and (c) the PMB is a cytoplasmic structure appearing extensively in vegetative cells of higher plants.