Morphogenesis

Plant morphogenesis is the development of a plant’s form and structure. Many overlapping processes, along with environmental factors, shape plant morphogenesis.

These processes include growth, cell differentiation, and cell-to-cell communication.

Growth includes cell division and cell expansion. During cell division, symmetry, rate, and orientation strongly influence cell fate. For example, stomatal development often begins with a meristemoid mother cell (MMC), which divides asymmetrically to produce a meristemoid and a larger sister cell. The meristemoid may go through additional asymmetric divisions before becoming a guard mother cell. This cell then divides symmetrically once, in a different orientation, to form two guard cells.

Most plant growth comes from cell expansion, which permanently enlarges cells. Plant cells mainly expand by taking in water, which enlarges the central vacuole and increases turgor pressure, and by loosening the cell wall. Together, these processes increase cell volume, leading to permanent cell expansion.

Cell division and cell expansion help shape the plant and guide its direction of growth. However, these processes vary among different types of plant cells.

Another key part of plant morphogenesis is cell differentiation, in which immature plant cells become distinct cell types. This process is guided by changes in gene expression, which turn specific developmental programs on or off.

Cell-to-cell communication also helps control gene expression during differentiation.

For example, in the root epidermis of Arabidopsis thaliana, cell position helps decide cell fate. Immature epidermal cells that contact one cortical cell become hairless cells, while those that contact two cortical cells develop into root hair cells. This pattern is linked to differential gene expression.

These cellular processes do not happen in isolation. Environmental factors such as light, temperature, water, and nutrient availability also strongly shape plant form.

Together, growth, differentiation, signaling, and environmental cues shape the final structure of a plant.