Influence of atmospheric oxygen on leaf structure and starch deposition inArabidopsis thaliana

Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weig ht, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L,) Heynh, (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2.5, 5.1, 10.1, 16.2, and 21.3 kPa O-2, 0.035 kPa CO2 and the balance nitrogen under contin uous light. Fully expanded leaves were harvested and processed for light an d transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been describ ed for plants grown under carbon dioxide enrichment, However, at the lowest oxygen treatment (2.5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespirat ion, resulting in very thick leaves and a dwarf morphology, This study esta blishes the leaf parameters that change during growth under low Oz, and ide ntifies the lower concentration at which Oz limitation on transport and bio synthetic pathways detrimentally affects leaf development.