Plants have indeed many "senses", although they have no nervous system to process the input the way animals do - therefore, usually the intercellular communication is conducted solely by hormones. For example, root tips are able to distinguish between "downwards" and "upwards" and will always grow downwards. Seeds, sprout tips and leaves can sense brightness, they will grow towards the light and adapt the metabolism, which is in different "modes" at day and night. The root systems are receptive for many substances, including systems that allow them to verify whether the neighbor plant is a genetical "twin" or at last of the same species or simply a rival, and the plant will react with more or less expansion of the root system. Also, there is communication ongoing with the mycelium (fungi) that is in close contact with the fine roots and helps them to acquire water and minerals.
Another interesting example of plant perception and (so to say) "awareness" is that certain substances in the saliva of, for example, a caterpillor, are sensed when they are touching damaged plant tissue. It is similar to an immune reaction. The substance will trigger a series of biochemical reactions.
Whether the plant detects certain saliva (this has been discovered only recently and it doesn't have to be true for all plants), or it is simply the damaged tissue, the broken cells, exposed to the air, which alarms the system: in the presence of an animal that is eating their leaves, plants that use to produce toxins or substances that are bad for digestion or worsen the taste (bitterness), will react quite quickly by increasing their production rate. This may not take more than ten minutes or an hour. This is well tested for many different plants and their notorious parasites, including tobacco. Also, at last if the threat is massive, many species are communicating the presence of the predators - be it caterpillars or giraffes - by emitting pheromones to warn even all the trees in a considerable distance. Some plants will even start to produce substances that
attract predators to feed on the vermin.
Also, the apples and bananas in your kitchen or refrigerator will emitt a gas that will accelerate the ripening process - and therefore the deteriorating - of many fruits and vegetables. Therefore it is good to separate them from other fruits and vegetables. On the other hand you can make use of this effect when you, for example, bought green bananas - just put them together with several apples into a small box for a day. It has to be considered, though, that not all sorts of fruits are suitable for post-ripening, some simply will not do this after being harvested, this is a genetic peculiarity that is different between species.
Oh and yes, I mightily enjoyed the movie "Avatar".
I guess it was ripe.
