Measuring shortcomings in tissue culture aeration and their consequences for explant development

Abstract

An outstanding characteristic of plant tissue culture and micropropagation methodology is the high level of precision with which cultural requirements are usually defined. A large and growing literature describes, in detail, ingredients of culture media needed to achieve particular developmental ends for a given species or cultivar [3]. However, despite authors’ carefully assembled protocols, it can often be difficult to reproduce results from other laboratories. One of several factors contributing to the problem could be the absence of any clear definition of the ventilation characteristics of culture vessels. The gaseous atmosphere in culture vessels is susceptible to several influences, but is dominated by the consumption and production of gases by the tissue, by the volume of the enclosing vessel and by the extent to which the vessel is sealed. Gases of particular significance for plant growth include carbon dioxide, especially in relation to respiration and photosynthesis, and ethylene (ethene), which is physiologically active at sub-parts per million (v/v) concentrations. For plants growing in the open, with their roots in freely draining soil, impedances to gas exchange are too small to decrease inward diffusion rates sufficiently to slow respiration and photosynthesis, or to entrap sufficient ethylene to change developmental patterns. However, the need to protect tissue cultures from desiccation and contamination by micro-organisms requires at least partial sealing. This inevitably impedes the inward and outward movement of gases and thus may interfere with gaseous exchange necessary for normal growth and development. There is also the risk of entrapping potentially toxic volatiles emitted from any plastics used in the construction of tissue culture vessels or their closures.