People should stop claiming plants can think - scientists

Don't feel guilty next time you're tending your garden - weeds don't have feelings, botanists are now saying.

In recent years new breakthroughs in understanding how plants adapt and react to changing conditions has led some scientists to argue they have a form of consciousness. 

The idea that plants can think and feel might sound like hippie nonsense, but it's been a subject of serious reserach since 2006, when journal Trends in Plant Science published a review called 'Plant neurobiology: an integrated view of plant signaling'.

Since then, scientists have run experiments showing plants can "learn" to respond to outside stimuli, compete with other plants for resources and even count. They say to do these, plants must have some kind of nervous system and even intelligence. 

"If consciousness literally means being 'with knowledge', then plants fit the bill perfectly," French philosopher  Michael Marder told Gizmodo last year, saying they need to be to survive. 

"That plants like all living beings on earth have a form of consciousness is very likely since it could correspond to an adaptive necessity for survival," Université Paris-Diderot plant biology professor told the site.

Some scientists have even resurrected an idea first proposed by Charles Darwin - that plants have a centralised set of receptors akin to a brain.

But not all scientists are convinced, and want an end to the flora foolishness. They're written a new article for Trends in Plant Science saying claims plants are conscious are "highly problematical" and ignore one simple fact - they don't even have a nervous system, let alone a brain. 

"What we've seen is that plants and animals evolved very different life strategies," said co-author Lincoln Taiz, a professor emeritus of molecular, cell, and developmental biology at University of California at Santa Cruz.

"The brain is very expensive organ, and there's absolutely no advantage to the plant to have a highly developed nervous system."

Brains in humans use up about 20 percent of an adult's energy.

Taiz and colleagues say recent research has suggested that "only vertebrates, arthropods, and cephalopods possess the threshold brain structure for consciousness" - ruling out worms, molluscs, jellyfish and protozoa.

"And if there are animals that don't have consciousness, then you can be pretty confident that plants, which don't even have neurons - let alone brains - don't have it either."

Taiz told the Guardian claiming plants have consciousness is "bad science", but is sympathetic.

"Is attributing consciousness to plants necessary as a psychological tactic to convince the general public of the urgent need to preserve the biosphere, whether or not it is true? 

"If the answer is yes, we are put in the intolerable position of having to choose between asserting a falsehood to promote ecological awareness, and maintaining objectivity as an uninformed populace pursues ecological catastrophe."