Carbon sources and their osmotic potential in plant tissue culture: does it matter?

Plant cell, tissue and organ cultures require a carbohydrate supply in order to satisfy energy demands. Experiments to define type and concentration of carbon source that allow culture establishment and development are usually conducted. Several studies published in the literature have inappropriately used percentages as reference concentrations to determine the quantities of the different types of sugars contained in the treatments leading to conflicting results and conclusions. The use of percentage references adds an undesirable osmotic variable among different treatments and some authors fail to consider this aspect. Therefore, molar concentrations should be used to carbohydrate concentrations reference because it isolates the osmotic variable influence that acts concomitantly with the nutritional variable. (C) 2003 Elsevier Science B.V. All rights reserved.