A QUANTITATIVE STUDY OF TISSUE DYNAMICS DURING CLOSURE IN THE TRAPS OF VENUS'S FLYTRAP DIONAEA MUSCIPULA ELLIS

The mechanisms by which Venus's Flytrap (Dionaea muscipula Ellis) close are not clearly understood, and several conflicting models have been proposed. We have measured the dynamics of five trap tissues from three trap regions during full closure ofyoung, fully developed, previously unclosed traps. Closure was divided into three distinct stages: 1) Capture- occurred immediately after stimulation of the trigger hairs and involved the rapid inward flexure of the trap margin and tynes. This motion interlocked the tynes, effectively capturing the prey. This was the only rapid movement of the trap; 2) Appression-completed by 30 min poststimulation, was characterized by contact of the margins; and 3) Sealing-completed by 1 hr poststimulation, was characterized by a sealed "digestive" sac formed around the potential prey, also by tight appression and recurved bending of the trap-margins. Major tissue dynamics that facilitated changes in trap morphology (hence, closure) occurred in different regions of the trap during different periods of time. The first regions where activity occurred were the A and C regions (Fig. 1), after approximately 15 min poststimulation; tissues in the C regions were most active followed by those in the B region of the trap (30 min to 1 hr poststimulation). Thus, shape changes during each stage of closure were the result of temporally separated changes in trap tissue volume. The complete sequence of events was elicited by a single 5-sec period of trigger hair stimulation. Our study showed that changes in the curvature of the trap during closure involved the expansion of opposing tissue groups (i.e., on opposite sides of trap medullary tissues). The pressure from contact of opposing trap lobes during the Appression stage may play an important role in regulating further trap closure and morphology.