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

Touch-sensitive stigmas (TSSs), specialized receptive structures in angiosperms, dynamically respond to mechanical stimulation or pollen deposition. The typical sequence comprises 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.

Here we systematically investigated the association of environmental (temperature and humidity) and pollination-related factors (amount of pollen deposited [load], position of pollen tube, and growth rate of pollen tube) with the temporal dynamics of stigma movements in Mazus miquelii, a species with TSS.

Temporary closure and reopening were primarily associated with temperature and were independent of the pollen load. In contrast, permanent closure was strongly correlated with the pollen load and position and growth rate of pollen tube. Furthermore, temporary closure and reopening time were negatively correlated, although neither were significantly correlated with permanent closure time.

Rapid temporary closure and reopening events were primarily associated with environmental cues, whereas irreversible permanent closure was associated with pollination-related signals. These advances in our understanding of the ecological regulation of TSS behavior provide a foundation for future studies into the physiological and molecular mechanisms of touch sensitivity of stigmas.