CHANGES IN SOLUBLE SUGAR, STARCH, AND ALCOHOL-DEHYDROGENASE IN ARABIDOPSIS-THALIANA EXPOSED TO N-2 DILUTED ATMOSPHERES

Proper exchange of atmospheric gases is important for normal root and shoot metabolism in plants. This study was conducted to determine how restricted air supply affects foliar carbohydrates, while using the ma rker enzyme alcohol dehydrogenase (ADH) to report on the oxygenation s tatus of tile rootzone, Fourteen-day-old Arabidopsis thaliana (L.) Hey nh, plants grown singly in 7-ml tubes containing agarified nutrient me dium were placed in coupled Magenta vessels and exposed for six days t o either ambient air or one of six different air/nitrogen dilutions, R edox potential of the agar medium was measured immediately after harve sting and freezing leaf tissue, and then root systems were quickly ext racted from the agar and frozen for subsequent analyses, Redox potenti al measurements indicated that this series of,aas mixtures produced a transition from hypoxia to anoxia in the root zones, Root ADH activity increased at higher rates as the redox potential neared anoxic levels , In contrast, ADH mRNA expression quickly neared its maximum as the m edium became hypoxic and showed little further increase as it became a noxic, Foliar carbohydrate levels increased 1,5- to 2-fold with decrea sed availability of metabolic gases, with starch increasing at higher concentrations of air than soluble carbohydrate, The results serve as a model for plant performance under microgravity conditions, where abs ence of convective air movement prevents replenishment of metabolic ga ses.