XVI International Botanical Congess

Pea primary roots are tolerant to flooding at 10°C, but at 25°C flooding after roots are 10cm long causes rapid cessation of growth. At 25°C, flooded root tips showed discoloration, curling, or narrowing. Histological examination showed that cells in the primary meristem had died, often asymmetrically. Data suggest that cell death was apoptotic. TEM revealed chromatin aggregation and chromatin drops in nuclei. The tissues were positive for TUNEL. Analysis of extracted DNA revealed a DNA ladder. Changes of chromatin in these cells preceded changes in cytoplasm and organelles. Changes in nuclear structure and chromosomal integrity are symptoms of apoptotic cell death. An apoptotic response possibly can reduce sink strength and allow more rapid diversion of resources to lateral roots growing in more permissive conditions.