XVI International Botanical Congess

Increased vacuolization of developing root cells is induced by environmental stressors that can either delay or accelerate aerenchyma formation. The objective of this ultrastructural and anatomical study was to determine how low oxygen affects the regions of cell vacuolization, cell elongation and cell collapse along rice roots. Using light microscopy, the locations of these regions were established within seminal roots exposed to normal and reduced oxygen concentrations. Transmission electron micrographs of root tip cortical cells showed that vacuole size increased and vacuole number decreased after 22 hr of reduced oxygen treatment. Vacuolization was similar to control values within 24 hr of re-aeration. Root elongation was slowed by reduced oxygen but returned to normal rates within 24 hr of re-aeration. Elongation rates were used to relate cell developmental age with distance behind the root apex.