Les teneurs ioniques des plants d'Isoetes setacea au cours de la réactivation par réhydratation

Ionic amounts of S, P, K+, Ca2+, and Mg2+ have been determined by chemical measures in different parts of Isoetes setacea (shoot apical meristem, cortical zone, and central stele) for plants in normal growth, in drought resistance, and during rehydration. Study of modifications in the ionic amounts during experimental rehydration showed that the significant increase of K+, Ca2+, and Mg2+ by the 24th h of experimentation was one of the earliest signals observed for the cells of the apical meristem (which are at that time blocked in G1 presynthesis phase) as well as for the differentiated cells. By the 7th day of rehydration, just before their entrance into the synthesis phase, meristematic cells have recovered ionic rates equivalent to those measured for active plants. The same thing happens in the nonmeristematic tissues. This increase of ionic amounts in the whole plant can be explained by a differential entrance of ions with water. This new balance of the ionic amounts according to the pattern found in the active plants can be considered as a prerequisite event for the recovery of an active metabolism for a meristematic or differentiated cell in water stress.