Can I use harvested plants to gain electric power?
A company in the USA called Voltree Power has gone one step further to harvest electricity generated directly from live trees and other plants!

It seems trees are able to provide somewhere between 20 and a few hundred millivolts as well as some current, derived from a difference in pH between the trees and the soil, maintained by the trees metabolic processes.

The science behind this technology was published in 2008 by researches at MIT. 

The company claims to have demonstrated the technology by developing the first wireless sensor network powered exclusively by trees to detect forest fires! They are also developing the technology to monitor humidity and temperatures in the forest using electrical power harvested from the trees themselves and transmit the data using low-power wiremess mesh technology.

Another collaborative group from University of Michigan, MIT &amp; UC Berkeley published their research in 2009 into micro-power electricity scavenged from evaporative flows within the microchannels in trees.