Root oxygen deprivation and leaf biochemistry in trees.

Plants are aerobic organisms, that is, they depend on oxygen for their life. Therefore, oxygen deficiency impacts on the biochemical and molecular processes of the plant cell. However, plant cells have evolved inducible strategies to cope with low oxygen stress conditions. When O 2 is reduced, energy production in the form of ATP is reduced too. Cells respond to this energy crisis by switching to fermentative metabolism, producing ATP and regenerating NAD + through the glycolytic and fermentative pathways. Roots are the organs most easily subject to low O 2 stress, but changes in fermentative enzymatic activities are also seen in leaves. Nevertheless, leaves already possess a constitutive expression of these enzymes. Since leaves are the plant organs less likely exposed to low O 2 conditions, they should have evolved in addition an alternative role for the enzymes usually related to fermentative metabolism. Leaves seem to have the ability to take advantage of the enzymes of a metabolic pathway commonly useful in parts of the plant which can undergo anoxia or hypoxia stress: they make use of fermentative metabolism in a different way, to limit the damage that stress condition imposes to the whole plant.