SUBMERGENCE-INDUCED ETHYLENE SYNTHESIS, ENTRAPMENT, AND GROWTH IN 2 PLANT-SPECIES WITH CONTRASTING FLOODING RESISTANCES

Submergence-induced ethylene synthesis and entrapment were studied in two contrasting Rumex species, one flood-resistant (Rumex palustris) a nd the other flood-sensitive (Rumex acetosa). The application of a pho toacoustic method to determine internal ethylene concentrations in sub merged plants is discussed. A comparison with an older technique (vacu um extraction) is described. For the first time ethylene production be fore, during, and after submergence and the endogenous concentration d uring submergence were continuously measured on a single intact plant without physical perturbation. Both Rumex species were characterized b y enhanced ethylene concentrations in the shoot after 24 h of submerge nce. This was not related to enhanced synthesis but to continued produ ction and physical entrapment. In R. palustris, high endogenous ethyle ne levels correlated with enhanced petiole and lamina elongation. No d ramatic change in leaf growth rate was observed in submerged R. acetos a shoots. After desubmergence both species showed an increase in ethyl ene production, the response being more pronounced in R. palustris. Th is increase was linked to the enhanced postsubmergence growth rate of leaves of R. palustris. Due to the very rapid escape of ethylene out o f desubmerged plants to the atmosphere (90% disappeared within 1 min), substantial underestimation of internal ethylene concentrations can b e expected using more conventional vacuum extraction techniques.