Increased respiration in flooded tomato hypocotyls does not depend on aerenchyma-promoted internal aeration

MIGNOLLI, F.; COWPER COLES, PATRICIO; VIDOZ, M.L.

Córdoba

Congreso; XXXII Reunión Argentina de Fisiología Vegetal; 2018

Flooding is one of the most frequent and extensive abiotic stresses that negatively influence terrestrial plant growth and productivity and may result in plant death. In tomato, aerenchyma formation enables oxygen (O2) to move towards hypoxic hypocotyls of flooded plants restoring normal internal O2 concentration. Conversely, silver nitrate (AgNO3) treated plants failed to develop aerenchyma and O2 levels were maintained markedly below than in control plants. We then asked whether internal aeration was able to restore respiration in submerged hypocotyls. Surprisingly, rate of carbon dioxide (CO2) evolution was constantly higher in flooded and in flooded AgNO3-treated hypocotyls with respect to normoxic controls. O2 uptake was also enhanced in flooded and in flooded AgNO3-treated hypocotyls in comparison with controls. Triphenyl tetrazolium chloride (TTC) is a redox indicator used to mark cellular respiration. In fact, when hypocotyl slices are simultaneously incubated with TTC and potassium cyanide, which inhibits mitochondrial cytochrome c oxidase activity, TTC reduction is impaired. Interestingly, in slices of flooded and flooded AgNO3-treated hypocotyls, TTC dyeing was more intense than in controls. In conclusion, respiratory metabolism in tomato hypocotyls appears unexpectedly exacerbated in the hypoxic environment and, although aerenchyma improves oxygenation in submerged hypocotyls, it does not affect respiration.