This article provides an overview of the early Mimosa pudica literature; much of which is in journals not easily accessible to the reader. In contrast to the contemporary plant learning literature which is conducted primarily by plant biologists, this early literature was conducted by comparative psychologists whose goal was to search for the generality of learning phenomena such as habituation, and classical conditioning using experimental designs based on animal conditioning studies. In addition to reviewing the early literature, we hope to encourage collaborations between plant biologists and comparative psychologists by familiarizing the reader with issues in the study of learning faced by those working with animals. These issues include no consistent definition of learning phenomena and an overreliance on the use of cognition. We suggested that greater collaborative efforts be made between plant biologists and comparative psychologists if the study of plant learning is to be fully intergraded into the mainstream behavior theory.

AbstractMimosa pudicais a Neotropical legume that closes its leaves rapidly in response to touch stimulation, hypothetically as herbivory defence. Habituation to non-harmful stimuli and long-term memory of past events have been demonstrated in this species, the former with relatively heavy objects and the latter under laboratory conditions. This species should not habituate to harmful stimuli if leaf movement is a response to herbivore damage. We tested in Monteverde, Costa Rica, whether (1) memory occurs in wild plants, (2) whether habituation occurs under harmful stimuli: simulated herbivory, and (3) whether wild plants can habituate to light non-harmful stimuli. The degree of closing of the leaflets and time until reopening was measured in response to repeated harmful and non-harmful stimuli. The results showed habituation to repeated non-harmful very light stimuli and showed lack of habituation to simulated leaf damage. Wild plants also showed faster rehabituation to repeated non-harmful stimuli when they had been exposed 15 days previously, suggesting possible long-term memory. These results indicate that wild plants are capable of (1) distinguishing between harmful and non-harmful stimuli (only habituating to the latter), (2) memorizing previous events, and 3) habituating very light tactile stimuli commonly experienced in the field.

Mimosa Pudica (also known as Pokok Semalu) is an action plant with unique biological cell mechanism that has great potential to be explored for next generation biomechatronics devices. The motion principle of each petiole movement occurs by an organ of motion, called pulvinus. The behavior analysis of the Mimosa Pudica plant main pulvinus and petiole against external stimulations has been investigated. The response of the plant cell was observed by optical and scanning electron microscopes (SEM). External stimulation tests on Mimosa Pudica plant such as mechanical, electrical and light stimulations were conducted. Optical microscopy and SEM observations revealed the existence of red cells in the tertiary pulvinus. Mechanical stimulation results had shown a response time of approximately 2 seconds and a recovery time of 10 to 12 minutes for the leaves and 20 minutes for the petiole. Bending force of the petiole of Mimosa Pudica was also measured. The torque generated by the bending of petiole was found to increase exponentially as the pulvinus diameter increased. A torque of 30.91 g mm was generated from the bending of a petiole with 1.5 mm pulvinus diameter. The lifting potential of the Mimosa Pudica was tested using loadings with increments of 0.42 gram. The plant responded to electrical stimulation of 1.3 Ampere and displayed side effect. The light sensitivity region of Mimosa Pudica was obtained through light stimulation using a full spectrum daylight bulb, and ranges from 50 to 300 lux. Signal transmission to neighbouring structures was observed when the leaf was stimulated with threatening stimulus, with the signal speed achieving 0.8 cm/s. Movement mechanism of Mimosa Pudica is believed to be triggered by signal through receptor cells. It was found that the torque generated during petiole lifting is relatively higher than that during petiole bending.

Although plants and animals both assess their environment and respond to stimuli, this reaction is considered a behavior in animals and a response in plants. Responses in plants are seen within various timescales- from the nanosecond stimuli is presented to a lifelong progression. Within this study, we bridge the gap between animal behavioral studies and plant response. Sensitive plants (Mimosa pudica L.) are an ideal subject for this due to the rapid closure of their primary leaflets when touched. We designed a multimodal, or stress combination, experiment to test two hypotheses with sensitive plants: if they could be distracted and if they would alter their risk assessment when exposed to external stimuli (wind and sound). To evaluate the distraction hypothesis, we measured an individual's latency to close, hypothesizing that if the plants were distracted, they would take longer to close. To evaluate the uncertain risk hypothesis, we quantified the latency to reopen, hypothesizing that if the plants were uncertain, they would take longer to reopen. We also quantified the number of pinnae closed on the selected stem to test for changes in risk assessment across treatments. We expected the unimodal treatments would distract or alter risk assessment, and the multimodal treatment would elicit an enhanced response. Multimodal stimuli had a significant effect on the number of pinnae closed before the tap, but we found no evidence that plants were distracted by any stimulus tested. We found that temperature had a significant effect on the latency to close, and that plants modified their risk assessment when exposed to experimental wind stimuli. By manipulating environmental stimuli, we found that sensitive plants trade-off energy and perceived risk much in the way that is commonly found in animals. Framing the study of plants' responses to environmental stimuli as behavioral questions may generate new insights.