Structurally, the apoplast is formed by the continuum of cell walls of adjacent cells as well as the extracellular spaces, forming a tissue level compartment comparable to the symplast. The apoplastic route facilitates the transport of water and solutes across a tissue or organ. This process is known as apoplastic transport.
The apoplast is important for all the plant's interaction with its environment. The main carbon source (carbon dioxide) needs to be solubilized in the apoplast before it is taken up by chloroplasts and consumed during photosynthesis. In the roots, ions diffuse into the apoplast of the epidermis before being taken up into the symplast by specific ion channels and being pulled by the plant's transpiration stream, which also occurs completely within the boundaries of the apoplast. Similarly, all gaseous molecules emitted and received by plants such as plant hormones and other pheromones must pass the apoplast. The apoplast is also a site for cell-to-cell communication. During local oxidative stress, hydrogen peroxide and superoxide anion can diffuse through the apoplast and transport a warning signal to neighbouring cells. In addition, a local alkalinization of the apoplast due to such a stress can travel within minutes to the rest of the plant body via the xylem and trigger systemic acquired resistance.
Vitamin C protects stressed-out plants: Ozone tolerance in snap beans is associated with elevated vitamin C in the leaf apoplast.
Jan 01, 2003; People aren't the only ones in need of antioxidants to neutralize free radicals. Scientists have long known that plants use their...