Scientia horticulturae vol:118 issue:3 pages:242-245
For decades bromeliad growers have to face severe leaf damage problems occurring as necrotic spots on leaves of sensitive CAM-plants such as Aechmea, both in cultivation and transport. These physiological problems mainly arise during the summer period from June to September. Previous research made clear that high malic acid concentrations in the early morning generate the driving force for cellular osmotic uptake of water and can consequently induce lethal turgor pressures in sensitive Aechmea cultivars. Although it is commonly known that CAM and its related metabolites can be influenced by different environmental factors, this relationship is poorly investigated under commercial greenhouse conditions.
Therefore the authors carried out 4 seasonal diurnal experiments with a high leaf damage sensitive Aechmea cultivar spread equally over a 1-year period. Malic acid dynamics revealed that during the critical summer period plants fail to induce malic acid consumption in the early morning causing prolonged high levels of malic acid in the leaves. Moreover, Relative Water Content measurements did confirm that enough water is always available inside the leaves and that even slight changes in water status can be disastrous for the leaves. During the rest of the year malic acid is consumed early in the morning and is not long enough available in the leaf to cause lethal water flow. The comprehension of why this damage induction mechanism is closely related with the summer period is essential to search for possible solutions to prevent the appearance of this physiological leaf damage problem in the future.