Abstract
Redox status in apoplast is an important factor for cell wall metabolism and cell growth in plants. Previously, we found that glutathione strongly stimulated cell elongation of excised stem segments of light-grown azuki bean and suggested an importance of apoplast rather than symplast for the effects. Here we determined endogenous levels of glutathione in light-grown lettuce seedlings to see the possible roles of transportable glutathione in the growth. We found that glutathione levels in cotyledons rapidly decreased while those in hypocotyls and first leaves newly emerged increased with age. Horizontal clinorotation stimulated growth of hypocotyls and first leaves of the lettuce seedlings, where their glutathione levels also increased. Such an increase in growth rate was not observed in azuki bean plants, which contained homoglutathione as a major thiol. From these results, we concluded that glutathione has an important role in growth of stem and leaf organs in lettuce plants.
