We often think of plants in much the same way we think of rocks: dumb things that don't move. Okay, plants do grow, but we tend to consider them as a static part of the environment. I think that is in part due to their alien nature that we don't form a natural affection for plants in the way we do with dogs or koalas. Other than some shared biochemistry, plants are very different than animals.
Or are they?
We've known for a long time that plants can respond to direct stimuli, have circadian rhythms, and can respond to cues from their neighbors—chemical warnings of pest interactions on neighboring plants, for example.
A recent study in Australia has shown that plants, at least garden peas, can also learn by association. As reported by the researchers, pea seedlings learned that a gentle breeze was associated with light coming from a particular direction. The plants would only learn, however, when the training stimulus happened during times that the plant perceived as "day". In other words, when it was "awake." Or whatever passes as being awake for plants.
This doesn't mean plants will be learning their ABCs anytime soon, but it does have some interesting implications for evolutionary biology. I'm interested to see if other plant species respond similarly.
You can read the paper online here: http://www.nature.com/articles/srep38427?WT.mc_id=FBK_SREP_1612_PLANTLEARNING_OA
Gagliano, M. et al. Learning by Association in Plants. Sci. Rep. 6, 38427; doi: 10.1038/srep38427 (2016).