The 1973 book "The Secret Life of Plants" by Peter Tompkins and Christopher Bird advanced the notion that plants are sentient and can experience emotions and pain. The book has been widely discounted as pseudoscience since its publishing, but recent studies indicate that plants are more aware than we understand.

I came across the book in high school after encountering my first vegan who explained that she did not eat anything that could feel pain. Being a natural born contrarian, I set out to prove that even though plants lacked a central nervous system, they could indeed feel pain. "The Secret Life of Plants" is a great book if you want to believe — and I do.

"Primary perception" (sometimes called "plant perception") is a theory advanced by Cleve Backster after he attached plants to polygraph machines in the 1960s. He reported that the lie detector machine registered when the plants were harmed and even when there was only the threat of harm. Over the years his findings have been discredited. Even the popular television show "MythBusters" tackled the experiment and labeled it "Busted" after Backster's findings could not be replicated. 

7 signs plants are more sentient than we think

Modern science may prove Backster and others were onto something.

In a study published in the journal Science in 2010, researchers reported that plants emit "green leaf volatiles" (GLVs) in response to herbivore damage. This "botanical SOS" carried by the modified compounds attracts predatory bugs to deal with the threat by eating them.

Scientists from Ben-Gurion University in Israel discovered that the common pea used its roots to signal neighboring plants when it experienced drought-like conditions. This caused surrounding plants to react as if they too were experiencing drought and prepare for the drought.

Plants are talking to insects and other plants; we just cannot hear them with the naked ear. The smell of a freshly cut lawn, the aroma rosemary emits when you crush the leaves between your fingers: that's the scent of plants screaming in agony.

Using a laser-power microphone, scientists at the Institute for Applied Physics at the University of Bonn have also documented that plants "cry out" when they are subjected to pain. When a leaf or stem of a plant is cut, it releases the gas ethylene over its entire surface. Using specially calibrated lasers, scientists were able to make the ethylene molecules vibrate. Microphones could record the result of the vibrating molecules. "The more a plant is subjected to stress, the louder the signal we got on our microphone," Frank Kühnemann, of the Institute for Applied Physics in Bonn, said of their findings. When plants are happy and healthy, they make a gurgling sound.

You do not need a fancy research lab to observe plants communicating with each other. Take an apple and seal it in a plastic bag with a bromeliad, a common houseplant, for 10 days. As the apple ages it releases ethylene gas that, in turn, induces the bromeliad to send out a shoot and flower. The bromeliad, having received a distress message from the apple, will bloom in the hopes of attracting a pollinator that will help it set seeds in order to ensure the survival of its genetic material.

Watch 'sensitive plant' react to touch

You know that eerie sensation that shoots through your body when someone unexpectedly touches the nape of your neck? Mimosa pudica reacts in a similar manner to protect itself from foragers. When triggered, the leaves of the plant fold and shrink away to look less appetizing to herbivores.

Gardeners who play music and talk to their plants have always had a reputation of being eccentric. However, research shows that plants can emit and respond to sound. Plants can even recognize family members, and plants know when to flower by keeping track of time using sunlight. 

While these studies may not completely validate Tompkins and Bird, they demonstrate the need for further research and discussion. Plants, like animals, are capable of basic learning and communication. They experience pain; they communicate with other species, and have happy and stressed states. If we observed this level of sentience in an organism with a face, we would extend to it rights.

Plant rights are equal rights

If the argument for the rights of plants cannot be grounded in ethics, then perhaps it should be an environmental issue.

As Michael Marder, Ikerbasque research professor of philosophy at the University of the Basque Country, Vitoria-Gasteiz, recently put in in the op-ed, The Time is Ripe for Plant Rights: "The case for plant rights is, paradoxically, both straightforward and complicated. There is no doubt that plants are some of the most vulnerable living beings on the planet: even according to fairly conservative estimates, one in every five plant species is currently on the brink of extinction.

"Given this disastrous global situation, plant rights could be a useful legal instrument for decelerating the loss of biodiversity and mitigating the destruction of the flora, the cornerstone of any natural environment."

After all, if corporations are assigned rights, why not a majestic oak tree? A brownfield an underserved neighborhood converted into a community garden? Or even a meadow in the way of an onramp for yet another subdivision?

We are currently in search of signs of life on Mars, but we do not fully understand and respect the life on this planet. It's time to change that.

Ramon GonzalezRamon Gonzalez is the original urban garden blogging male espousing a DIY philosophy to gardening and garden projects. Better known online as MrBrownThumb, he's been demystifying gardening secrets for average gardeners online since 2005. Besides writing the popular MrBrownThumb garden blog, he's co-founder of @SeedChat on Twitter, the creative director of One Seed Chicago, and founder of the Chicago Seed Library.

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The case for the ethical treatment of plants
Plants communicate with each other and with the world around them, and they deserve our respect, says Ramon Gonzalez.