We have been examining the response of maize seedling roots to oxygen stress. Previously, we have shown that maize seedlings with primary root lengths of 10cm or greater require a pretreatment with low oxygen (hypoxia) for survival of greater than 12 hours of anoxia. During the pretreatment there is induction of mRNA and increase in enzymatic activity of alcohol dehydrogenase (ADH) and other enzymes that are necessary for alcoholic fermentation. However, we have found that younger seedlings do not need a pretreatment to survive anoxia. They appear to have high levels of ADH and other enzymes that are needed for anaerobic survival at levels equivalent to those that are induced in older seedlings. These results suggest that, at the time of seedling emergence, seedlings may be more adapted to oxygen stress than during later stages of growth.
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