Question

1. Explain the role of plant cell division in plant cell patterning

Answer 1

Plants have evolved with specialized regulatory mechanisms to achieve proper tissue growth and morphogenesis. During development, an organism acquires a characteristic shape and size and establishes vigorous organ morphologies. in order to achieve this, growing tissues undergo multiple rounds of growth, division, and differentiation until a highly organized structure is formed

The most-studied roles of patterned cell divisions in the development of flowering plants are those of shoot development (including formation of leaves and flowers) and primary root development, embryo development.  The basic body organization of a plant is laid out after the fertilization, when the plant embryo forms in the developing seed, as the seed matures development stops . On germination, the mature embryo produces a seedling consisting of the embryonic leaves (cotyledons), a root, with a root meristem, and a stem (hypocotyl) with a shoot apical meristem from which the leaves, the stem and the flowers arise.

example. in the model plant Arabidopsis, the axial pattern of the embryoduring embryogenesis is established during the first asymmetrical cell divisionof the zygote, giving rise to an apical cell(small , cytoplasmically dense) and a basal cell( large and vacuolated) . it establishes the axial polarity. nearly the entire embryo is derived from the small apical cell. the apical cell undergoes two longitudinal divisions followed by a transverse division to from an eight celled , octant stage globular embryo. additional cell division increases the number of cells in the globular embryo . the larger vacuolated basal cell also divides, but all of its division are horizontal, at right angle to the long axis, it gives a filament of six to nine cells known as the suspensor that attches the embryo to the vascular system of the plant. the basal cell derivative nearest the embryo is known as the hypophysis and it gets divited to form the quiescent center of the root apical meristem and the root cap.

by the globular stage , the embryo divides into three domains. the top and bottom halves of the embryo correspond to the apical and central domains. whereas the uppermost cell of basal cell derivatives,the hypophysis constitutes the basal domain. the shoot apical meristem and most of the cotyledons derive from the apical domain, part of the cotyledons, the hypocotyl, radicle, and part of the root apical meristemcomes from the central domain, and the quiescent center of the root apical meristem and root cap are from the basal domain.