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 hypox ic stress (0.1% O-2 for 48 h) in both roots and shoots, but hypoxic acclima tion did not improve tolerance to anoxia (0% O-2). The acclimation of shoot s was not dependent on the roots: increased shoot tolerance was observed wh en the roots of the plants were removed. An adh (alcohol dehydrogenase) nul l mutant did not show acclimation of the roots but retained the shoot survi val response. Abscisic acid treatment also differentiated the root and shoo t responses; pretreatment induced root survival in hypoxic stress condition s (0.1% O-2) but did not induce any increase in the survival of shoots. Cyc loheximide blocked both root and shoot acclimation, indicating that both ac climation mechanisms are dependent on protein synthesis.