Mode of Carbon Dioxide Action on Metabolism of Organic and Amino Acids in Crisphead Lettuce

Abstract

<jats:p>Leaf tissues of crisphead lettuce (<jats:underline>Lactuca sativa</jats:underline> L.) were kept in air or in air enriched with 5% to 20% CO at OC for 2 to 9 days followed by transfer to air or to CO<jats:sub>2</jats:sub> <jats:sup><jats:underline>2</jats:underline></jats:sup>enhanced atmospheres at 20C for 1 day to study the mode of CO<jats:sub>2</jats:sub> action on metabolism of organic and amino acids. The 20% &lt;ch&gt; treatment caused a decrease in intracellular pH, which alone or, in combination with, other CO<jats:sub>2</jats:sub> effects, inhibited succinate dehydrogenase but activated glutamate decarboxylase. This resulted in an accumulation of succinate and γ-aminobutyrate and a reduction in concentrations of malate and glutamate. Elevated CO<jats:sub>2</jats:sub> atmospheres did not affect other organic and amino acids. These effects of CO<jats:sub>2</jats:sub> were influenced by temperature and concentration/duration of exposure to CO<jats:sub>2</jats:sub>, while type of tissue (green vs. white) and cultivars of lettuce generally had no influence.</jats:p>