edited (i fixed the link)
Researchers from Michigan State University have discovered that plants have a rudimentary nerve structure, which allows them to feel pain. According to the peer-reviewed journal Plant Physiology,
plants are capable of identifying danger, signaling that danger to other plants and marshaling defenses against perceived threats. According to botanist Bill Williams of the Helvetica Institute, "plants not only seem to be aware and to feel pain, they can even communicate."
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as for wikipedia
Click Here (plant perception)
HOWEVER
Overall, there is little concrete, universally verified evidence suggesting that there is any truth to the theory, and it is therefore apt to receive a great deal of contempt among scientific circles, often disdainfully called 'the Backster Effect'. Skeptics typically criticize the fact that many experiments into 'plant perception' are not taken in controlled conditions and that therefore their results are not verifiable evidence of its existence. Many skeptics of the theory also state that, since plants lack nervous or sensory systems, they are not capable of having feelings, or perceiving human emotions or intentions, which would require a complex nervous system. The primary emotional center in the animal brain is believed to be the limbic system which is absent in plants, just like the rest of the nervous system
(also from wikipedia)
(once i get the study i will provide the link)