The smell of fresh cut grass means very different things to green plants vs to us humans.
The smell comes from a class of chemicals called Green-leaf Volatiles (GLV) which can protect the plant against predators. When the leaf of a tobacco plant, for example, is attacked by the tobacco hornworm, GLV is released by the injured leaf and is detected by another bug which has corresponding receptor molecules on its antennae. This carnivorous bug comes and feeds on the hornworm, saving the plant (See link)
This type of chemical information exchange for survival is extremely important throughout the living world, including humans. In us, there is a peptide-receptor network that is spread all through the body, far more extensive and carrying tons more information than our nervous system. An example is endorphin, which is produced during ‘runner’s high.’ It is a peptide (a very small protein molecule). When it attaches itself to its receptor on a cell’s surface, it will trigger the sensation of calm and euphoria – the effect of endorphin on us.
This chemical network is largely responsible for a type of learning and memory we call implicit, or non-declarative, experiential learning, involving the bodily senses. It is also often non-conscious. ( For a discussion of this please see my essay, Information = Knowledge?)