I think they have brains myself.

meh it's all enzymes

It has evolved over millions of years - that's why. Oh, wait. All plants do this the same way. Hmmm. I don't know how plants could be created so that they take advantage of the environmental situations.

A number of studies have shown that plants feel pain, and vegetables are picked and often eaten while still alive. Animal rights activists are often in the news, but has anyone ever protested for vegetable rights? Mythbusters prove plants feel pain? Members of PETP (People for the Ethical Treatment of Plants) should be happy with this week's episode of Mythbusters. They hooked up a machine to a plant then tortured the plant. The machine showed the plant reacting. Even just thinkng of torturing the plant caused a reaction. The episode was based on Cleve Backster work. In the study of paranormal phenomenon Plant perception, or biocommunication in plant cells, has come to mean a belief that plants feel emotions such as fear and affection. Believers hold that plants have the ability to communicate with humans and other forms of life in a recognizable manner. While plants can communicate through chemical signals, and certainly have complex responses to stimuli, the belief that they possess advanced cognitive abilities receives little support except in the parapsychology studies community and among believers in the Gaia hypothesis. Published in 1973, The Secret Life of Plants was written by Peter Tompkins and Christopher Bird. It is described as "A fascinating account of the physical, emotional, and spiritual relations between plants and man." Essentially, the subject of the book is the idea that plants may be sentient, despite their lack of a nervous system. This sentience is observed primarily through changes in the plant's conductivity, as through a polygraph, as pioneered by Cleve Backster. The book also contains a summary of Goethe's theory of plant metamorphosis. So tonight when you eat a head of lettuce, be glad you can't hear it screaming in pain.

Some plants certainly have the ability to react to some surprising stimuli. But for the most part they are doing just that, reacting. When plants 'move' towards a light source they are doing so in response to the release of hormones triggered by the light itself. It is all just a simple trigger - response mechanism To use the term consciousness when describing the innate stimulus response mechanisms of plant life is a bit of a logical fallacy and anthropomorphic in the extreme. Plants may respond to damage but they are in no way aware of the subjective experience that is pain. They have no CNS from which anything approaching consciousness could emerge.