The Natural Coast By: Jack & Anne Rudloe

Sensitive Plants

Sensitive plants represent some sort of interface between plants and animals. Touch them and the leaflets draw together and shrink away from you. My fascination with them goes way back, before high school when I was in elementary school in New York journeyed to the Brooklyn Botanic Gardens one day, there they were, three of four potted plants. When you touched the leaves of Mimosa pudica they actually closed up and shrank away from you, it was amazing. I went around and around the green house with the crowds thumping them until I wore them out. (They get tired and lose their sensitivity, if you keep hitting on them and regain it after they rest). My teacher Mrs. Silvers said they contained a magic fluid that made the leaves close up when you touch them. Whether it was true or not, the idea intrigued me.

When I moved to Florida as a teenager, I was in sensitive-plant heaven. Shrankia or Neptunia, close cousins of the plant that I saw at the Brooklyn Botanic gardens thrived in the Florida pine palmetto flatwoods and once again, I couldn't help stopping and thumping the leaves. Not all were sensitive to the touch, but all of them closed their leaves up at night. Again the questions came back to me. Why, did they do that? How did their close their leaves? How can those tiny pulvini, the swellings where the leaflets attach the midrib lift a leaflet ten times its size and defy gravity? It has to do with fulcrum effects, and it still puzzles physicists.

No one has answered the question as to why do the leaves go to sleep at night, folding together almost as if in prayer? Sensitive plants are just an extreme example of a huge group of legumes that fold their leaflets when dark comes. Albrizzia, the non-native Mimosa tree that grows like a weed in your yard that explodes in floral pink this time of year is a good example. You can't cheat them either, even if you keep them in darkness day and night, as a French natural historian found in the 1600's, they have their on endogenous rhythm of opening a closing.

The plants brought me to Florida State University, where I worked with scientists as a high school student. I was given a green house and instructions on how to measure their movements of their leaves with a goniometer. It turned into a science fair project; I entered and won regional and state competitions. They started me on my writing career; my first publication was in Scientific America, "Leaf Movements of the Wild Sensitive Pea, Cassia nictians."

But then it all fell apart. Shortly after I enrolled the university and I parted company. It was a sad day when I had to turn in my keys to the greenhouse, and give my plants away. Economic and other interests forced me to shift my focus; academic life was not for me. But this little shrub that folded its leaves at night, and shrank away when I touched it, gave me a lifetime of fascination. But no matter where I traveled in the world,
they were never far away. I met the thorny bushes of Mimosa growing in Africa and Madagascar. I found a dazzling plethora of species in Central and South America, in the Bahamas, in Malaysia, Borneo and Thailand-- everywhere except China. Whenever I went I thumped the leaves, and watched them close.

During my travels I collect stories about it. In Central and South America the natives claim this low growing, thorny shrub with its spectacular explosions of pink spherical blossoms, almost has a hypnotic effect on people and is used extensively in voodoo. The Miskito Indians of Nicaragua call it King Alau, and say that if you're dragged into court, you put a bit under your tongue and tell your story, and the judge will let you go. If the police catch you with it in Surinam, they'll take it away from you. Mimosa pudica It’s used to cover up infidelity, put some under your spouses pillow and he and she will sleep through his misbehavior.

In sports, kids have been known to chew it up and spit it on baseball plates, to make the opposing team become sluggish and inattentive. In Malaysia there is an elaborate myths how her father turned a disobedient princess into a sensitive plant, and the name translates to "shy virgin". The stories go on and on. But it's real magic comes from keeping village kids busy for hours, thumping the leaves. Recently I saw a program on the Discovery channel, showing monkeys in India, thumping the leaves with rapt attention, seeming to ask the same questions. Sensitive plants were my introduction into science.

I have this fantasy, in my old age, someday if I retire and achieve economic stability, I'll have this giant green house with collations of sensitive plants from all over the world. They'll growing in pots, as trees, and shrugs, in a great array of flowering profusion. I'll bring them in from all over the world: bull thorn Acacias from thorn thickets of Africa, Mesquite bushes from the desert, Mimosas, Cassias, and Acacias in great array. And there I will end my days, watching them opening and closing their leaves in unison, and putting forth their beautiful fragrant flowers. And every night I watch the Mimosa tree, Albrizzia fold its leaves and go to sleep, something scientists call "nyctotroic movements".

I might putter around with electronics, wiring up plants, measuring and recording the transmission of stimuli as moves along the midrib, causing the leaflets to fold; or contemplate the mystery of the plant's pulvinus, and how this tiny hinge manages to defy gravity and hoist a leaflet ten times its size into the air. But in the end, I would never really know how or why their leaves close up at night, or when you touch them, any more than I know why horseshoe crabs come to the shore to lay their eggs after a lifetime of study, or why parchment worms living down in their dark tubes beneath the mud glow in the dark with a beautiful eerie blue light.

Everything alive emits electricity and broadcasts waveforms. A single cell in a corn plant discharges a billionth of a volt, and doctors declare legal death when electrical activity ceases in the brain. With their pinnate leaves shaped like television antennae, sensitive plants, and all other living things are massagers of God transmitting the condition of our world to the universe, all saying "we're here, we're here." And likewise the fiddler crabs on the beach, waving their claws are crying out that same message until the developers come and smother them with dirt and they are heard no more. Who can say that when the signals or voices of the needlerush, cordgrass and marsh mallows are silenced, will the deity that made billions of galaxies and a hundred trillion stars notice it?

Sensitive plants like disturbed sites. Partridge plants, Cassia species thrive in bare mineral soils. Like other weeds, they become scar tissue that covers the wounds that bulldozers inflict on the earth. Our greed and the anti-environmental policies of our government grows worse daily and our beautiful habitats fall daily to the bulldozer, leaving raw scraped up, "cheap dirt” behind. Sensitive plants are legumes,they have little nodules on their roots that put nitrogen back into the soil. Is doom at hand or will the beautiful little sensitive plant that grows in the diminishing forests with its festive pink blossoms save us?