34.9 : Morphogenesis

Plant morphogenesis is the development of a plant’s form and structure. Many overlapping processes and environmental factors contribute to plant morphogenesis. 

Among these processes are growth, cell differentiation, and cell-to-cell communication.

Growth includes cell division and elongation. During cell division, the symmetry, rate, and plane—or orientation—of division greatly influence a cell’s fate.

For example, guard cells, which control gas exchange in plants, typically form through asymmetrical division and by a change in the plane of cell division. 

However, most plant growth is caused by elongation, which is the permanent enlargement of differentiated cells. 

Plant cells expand primarily by taking in water. Most of the water is stored in a large central vacuole.  

Cell division and cell enlargement determine a plant’s shape and direction of growth. However, these processes vary among different types of plant cells. 

The specification of immature plant cells into distinct cell types is called cell differentiation and is also a critical component of plant morphogenesis. 

Cell differentiation is guided by gene expression changes, which inactivate or activate protein-coding genes. Cell-to-cell communication likely regulates the expression of genes that influence cell differentiation.  

For example, the root epidermis of Arabidopsis thaliana produces hair cells and hairless epidermal cells. Immature epidermal cells contacting one cortical cell differentiate into hairless cells, while those contacting two cortical cells develop into root hair cells. This pattern is associated with differential gene expression. 

Environmental factors, such as light, temperature, and the availability of water and nutrients, also greatly influence plant morphology.