Plant Sciences/Introduction

Plant cells are immobile, encased in a rigid cell wall. Unlike animal cells, migration and programmed cell death play little role in the patterning of plant cell fates, nor can they move when their environment changes. If the supply of food is low or if there is a predator, animals can move, fight or fly. But plants cannot. They have to adapt constantly to their environment and their development is highly plastic. Animal development is mainly embryonic: the body shape is defined during embryogenesis and the adult derive from the enlargement of the embryo. In contrast, in plants, most of the development occurs post embryonically and never ceases. In fact, because plants can't escape from their physical locations, they adapt and "escape" through development. When there is a lack of nutrients or energy, the plant develops its root system to explore the ground or its aerial system to get some light. Under attack from a pathogen or herbivore, the plant is able to synthesise signalling molecules to change its development and defend itself.

Despite their sessile lifestyle, plant development is highly plastic, due to the important role of information exchange between neighbouring plant cells. It appears that cell are more dependent on their positional information rather than lineage origine as in animals. Almost every plant cell containing nucleus has been shown to be able to re-enter the cell cycle and divide. This occurs for example after wounding, neighbouring cells are able to divide and differentiate to replace dead cells.

In normal plant development, post embryonic growth comes from meristems. Meristem is a type of embryonic tissue in plants consisting of unspecialised, youthful cells called meristematic cells and found in areas of the plant where growth is or will take place - the roots and shoots. Meristematic cells are small isodiametric cells, the nuclei occupy most of the cell. The cytoplasm contains undifferentiated plastids and posses a small vacuole.

Pool of cells are kept meristematic and divide, cells exiting the meristematic zone, start elongating and then differentiating.

We’ll look at some of these unusual features of plant development using examples from the model plant, Arabidopsis thaliana.