These two cells types have distinct programs of gene expression. Because plant cells have rigid cell walls, plant cells can't migrate . Therefore, plant shape is based on the rate and direction of cell division and cell elongation. Plant development is continuous . New plant organs are formed throughout their life by clusters of embryonic cells called meristems.
Plants have tremendous developmental plasticity .
Lost plant parts can be regenerated by meristems, and even entire plants can be regenerated from single cells. In addition, environmental factors such as light and temperature can greatly influence overall plant form. The egg cell and polar nuclei are contained within the embryo sac. Th e sperm nuclei are derived from the pollen grains. This first asymmetric division provides polarity to the embryo.