Plants engage actively with their environment, and communicate with other plants. Usually by secreting some kind of chemical ("secondary metabolite"), which makes sense given they don't move very fast.
Things that don't move very fast are at an advantage where energy efficiency is important. The general trend is that low-energy things modify their environment chemically and high-energy things modify their environment mechanically. Compare the diversity of human-discovered secondary metabolites from plants/fungi (low power), insects/reptiles/amphibians (medium power), mammals/birds (high power)
Plant communication is certainly fascinating, but I wouldn't call it a sign of consciousness. Isn't it just another reaction to stimuli?
I can imagine an experiment where some plants are placed in an environment where the communication chemical they secrete interacts with a gas in the air, slowly poisoning the plants. Would the plants adapt by changing their own behavior, or would some later generation survive due to a mutation? If they changed their own behavior, that might point toward a kind of individual consciousness.
Us humans are kind of undergoing that experiment right now with climate change and everything else, and even with the strategies available to us it is unclear whether humans will survive the coming hundreds of years :)
From a philosophical standpoint, and considering the spirit rather than the details: Is this hypothetical experiment just giving plants a challenge at them which they're too dumb or helpless to solve?
It seems there are plenty of analogous challenges which humans alone or in groups are unequipped to deal with.
Is any "challenge" humans respond to not a homeostatic correction, like if everything were perfectly perfect for a person would they do anything different at all? Considering also the homeostases we're built to maintain "just because", like novelty vs boredom.
If a thing "decided" to change its reproductive rate, or selected different sexual partners based on environmental conditions, is this necessarily a phenomenon unconnected to individual agency? Humans do this too.
Developmental neuroscience strongly supports the claim that physical brain architecture requires environmental stimuli, and psychology strongly supports the importance of "nurture" contributing to a person's "self". Do these stimulus responses have no bearing on consciousness?
If your conscious experience suddenly became transferred to a tree, and a lumberjack came to cut you down, how could you convince them you're conscious using the behaviors available to you?
Consider a conscious alien unfamiliar with human society, or a Stone age tribesperson who somehow doesn't embody human cognitive biases like assuming consciousness of things that look like them. If they observe a financial services office for a few hours, do they think the workers are modifying the environment in an individually considered manner?
If plants and humans were both considered by definition to be conscious, would life change?
The medical definition of conciseness includes things like responding to bright light by constructing the iris. It’s not high on the scale, but it’s very much part of the current definition in active usage. So, in practice it’s useful have level of consciousness and as such the minimum can be extremely low without becoming less meaningful.
More importantly as we understand more about the brain we may eventually understand how everything works. Any definition that would then exclude humans as conscious becomes irrelevant.
I can imagine an experiment where some plants are placed in an environment where the communication chemical they secrete interacts with a gas in the air, slowly poisoning the plants. Would the plants adapt by changing their own behavior, or would some later generation survive due to a mutation? If they changed their own behavior, that might point toward a kind of individual consciousness.