Plant development: Keeping your distance

The outer skin of a higher plant consists of a single layer of cells known as the epidermis. The epidermal layer is established during embryogenesis and is formed continually by cell division in meristems in the developing apices of the root and shoot. The epidermis expands by cell division and cell elongation as the plant grows. In addition to the relatively unspecialised epidermal cells, more highly differentiated cell types can be found in this tissue in both root and shoot organs. In the root epidermis, specific cells can differentiate into root hairs that play important roles in nutrient acquisition. In the aerial parts of the plant, specific epidermal cells can differentiate into either polarized hair-like structures known as trichomes or stomatal guard cells, which form bicellular pores in the leaf surface through which water and gasses can be exchanged with the atmosphere. A recent study [1] has shed new light on the mechanisms by which the nonrandom spatial pattern of stomatal cells in the plant epidermis is generated.