Who says plants don’t have feelings? Mimosa pudica, also known as the touch-me-not or sensitive plant, remarkably demonstrates a plant’s sentience.
Many plants close up at night and open in the morning, but this plant dramatically drops its leaves at the slightest touch. Even just being blown or shaken will cause it to wilt.
The plant’s movements occur when its cells lose turgor pressure—the water pressure that pushes up against the cell wall to keep leaves standing outwards. When agitated, the plant releases chemicals that force water out of the cell, causing the cell walls to collapse and the leaves to fall.
Scientists believe that the plant evolved this strange characteristic to defend itself against predators—animals fear fast-moving plants and the quick leaf-dropping movement flicks off dangerous pests.
Mimosa pudica has fascinated people worldwide. The following list of poetic names suggests different interpretations of the plant’s actions:
Touch me not – U.S.
Morivivi (dies then lives) – Dominican Republic
Dormilona (sleepy head) – Costa Rica
Mateloi (false death) – Tonga
Mutidare muni (angered by touch) – Karnataka (India)
Lojjaboti (shy virgin) – Bengal (India)
Dancing plants
The mimosa isn’t the only sentient plant. Codariocalyx Motorius, also known as dancing grass, semaphore plant or telegraph plant, appears to feel the beat of the music and groove along with it.
Groping flowers
The passion flowers’ (Passiflora) tendrils feel for objects, then wrap around them. As they wrap themselves around the object, the stem gets pulled into it for support so it can grow higher and grow more tendrils before repeating the process.
Hungry carnivores
The venus flytrap (Dionaea muscipula) is insectivorous (carnivorous). Since it lives in the poor boggy soil of the Carolinas, it attains better health by looking upward for meals rather than downward. When something bends the sensitive trigger hairs on the outside of the plant, its jaws shut, trapping insects inside. The plant then secretes digestive juices to dissolve the soft parts of the insect over a five to twelve day period, then opens up to “spit out” the indigestible bits.
The concept of sentience is a hotly debated one. Some feel that only beings that can experience pleasure and pain are considered sentient. Others believe that beings come in a wide range of sentience, starting with the Oxford dictionary definition: “able to perceive or feel things.” Given that definition, the Mimosa Pudica’s actions definitely make it a sentient being. Angry, shy, sensitive. All these terms have been used to explain its behaviour. It’s quite a character, that Mimosa Pudica! And its friends, the dancer, the groper, and the hungry man. There’s a full cast of herbaceous characters growing out there!
image: Pavan Srinath (Creative Commons BY-SA)
