Influence of abiotic and biotic stressors on the sensitivity defenses of Mimosa strigillosa

Background/Question/Methods

In plants, both physical and chemical traits are involved in the defense against environmental stress and herbivory. In the case of Mimosa plants, touch-sensitive responses through leaf-closure provide a unique form of mechanical defense. While past research has shown that the impacts of stressors such as competition or short-term drought may cause the chemical defenses in plants to increase or decrease, it is unknown how the interaction of these stressors may influence the efficiency of touch-sensitive responses. In this study, we hypothesized that the touch-sensitive responses of Mimosa strigillosa would strongly differ from regularly watered individuals when subjected to short-term drought. Additionally, we hypothesized that competition would hinder the touch-sensitive response, particularly from competitors in closely related taxa. To test these hypotheses, an experimental design was performed with three competition groups of Mimosa: competition within itself, competition with another member of its family, and competition with a member outside its family. Within each competition group, one half of plants were regularly watered, while one half did not receive water for three days. Plants were then subjected to a tactile stimulus in a greenhouse environment, with the degree of leaf closure being measured as an estimate of recovery.

Results/Conclusions

Drought-affected plants had greater leaf closure and more efficient leaf opening times than plants that were not affected by drought. The loss of turgor pressure involved in Mimosa may create a more drastic closure and re-opening response. However, competition did not show significance as a stress factor on Mimosa’s touch responses, possibly due to the M. strigillosa species being more competitively successful and resilient compared to other Mimosa species. These results suggest that abiotic factors may be more influential drivers of plant defense traits than competition. Future work could investigate the impact of the touch-sensitive response to reducing damage under various conditions in the field.