Arabidopsis roots and shoots have different mechanisms for hypoxic stress tolerance

Arabidopsis has inducible responses for tolerance of O-2 deficiency. Plants previously exposed to 5% O-2 were more tolerant than the controls to hypoxic stress (0.1% O-2 for 48 h) in both roots and shoots, but hypoxic acclimation did not improve tolerance to anoxia (0% O-2). The acclimation of shoots was not dependent on the roots: increased shoot tolerance was observed when the roots of the plants were removed. An adh (alcohol dehydrogenase) null mutant did not show acclimation of the roots but retained the shoot survival response. Abscisic acid treatment also differentiated the root and shoot responses; pretreatment induced root survival in hypoxic stress conditions (0.1% O-2) but did not induce any increase in the survival of shoots. Cycloheximide blocked both root and shoot acclimation, indicating that both acclimation mechanisms are dependent on protein synthesis.