Thigmomorphogenic responses of epiphytic bromeliads to mechanically induced stress

Abstract

AbstractVascular epiphytes represent almost 10% of all terrestrial plant diversity. Despite the extensive research on the functional ecology and challenges of epiphytic growth, there is still very little known on how exposure to mechanically induced stress affects the growth and development of epiphytes. Therefore, this study investigated the effect of such mechanical stress on the growth and biomass allocation of epiphytic bromeliads. Juvenile plants of two species were subjected to two types of mechanical stress in the greenhouse—permanent displacement and temporary, recurring mechanical flexing. ANOVAs were used to test possible treatment effects on growth, root–shoot ratio, root diameter, and root area distribution ratio. Contrary to previous studies on herbaceous plants, these bromeliads showed little to no change in root and shoot properties in either species. The root–shoot ratio increased in disturbed Guzmania lingulata plants, but not in Vriesea sp. Treatment effects on growth were inconsistent: a stress effect on growth was significant only in the first 2 months of the experiment in G. lingulata, whilst none of the stress treatments negatively affected growth in Vriesea sp. All disturbed plants showed some degree of curvature on their stems and leaves against the area of stress to obtain an upright position. This was probably related to the maintenance of a functional tank. This study provides quantitative and qualitative data to understand thigmomorphogenic responses of bromeliads to mechanical stress. Future studies could include field surveys to quantify on-site mechanical stresses and the corresponding morphological changes in vascular epiphytes.