Linking environmental and pollination-related factors to touch-sensitive stigma closure dynamics in Mazus miquelii

Premise: Touch-sensitive stigmas (TSS) are specialized receptive structures in angiosperms that dynamically respond to mechanical stimulation or pollen deposition. The behavior of a typical TSS comprises three sequential events: temporary closure, reopening, and permanent closure, which optimize pollen capture, retention, and fertilization success. However, the specific environmental and pollination-related factors regulating these phases are unexplored. Methods: Here we investigated the association of environmental (temperature and humidity) and pollination-related factors (the amount of pollen deposition, pollen tube position, and pollen-tube growth rate) with the temporal dynamics of stigma movements in Mazus miquelii (Mazaceae), a species with TSS. Results: We show that temporary closure and reopening are primarily associated with temperature, and are independent of the amount of pollen deposition. In contrast, permanent closure is strongly correlated with the amount of pollen deposition, pollen tube position, and the pollen-tube growth rate. Furthermore, temporary closure and reopening time are negatively correlated, although neither show a significant correlation with permanent closure time. Conclusions: Our study provides a systematic investigation into the specific factors associated with permanent closure time. Rapid temporary closure and reopening events are primarily associated with environmental cues, whereas irreversible permanent closure is associated with pollination-related signals. These findings advance our understanding of the ecological regulation of TSS behavior, and provide a foundation for future studies into the physiological and molecular mechanisms behind this behavior.