Contrary to what it is commonly assumed, plants seem to be capable of many of the cognitive abilities traditionally assumed to be exclusive to animals. Hence, the behavioral evidence thus suggests that plants could qualify to be sentient organisms. 

Segundo-Ortin, Miguel et al.

This article recently published in the Wiley Interdisciplinary Reviews: Cognitive Science explores the evidence that plants may possess some form of sentience or consciousness. That is, they have a phenomenal experience of the world around them. There is something it is like to be a plant.

The article examines the growing body of research into plant behaviours. It then proposes some possible explanations to support consciousness, both reductive (caused as a product of biological/material processes), and non-reductive ( including the possibility that consciousness is non-local or trans local).

A brief summary of the topics covered follows. A link to the full article is at the bottom of this post. It is an interesting read.

Plant cognition.

Plants may exhibit adaptive behavioural patterns that are often flexible and goal directed. That is they react to more than just the here and now.

Communication.

Inter plant communication occurs via ‘airborne biogenic volatile organic compounds (VOCs) that are exuded via their leaves and flowers. These VOCs can signal other plants to impending threats or be used as a kind of location beacon (that is sometimes exploited by other parasitic plants).

There is also evidence to show plants are receptive to sound vibrations (for example, producing nectar in response to the sound of flying bees), and via (sometimes vast) mycelial networks under the ground.

Kin recognition.

Studies have shown that plants respond in different ways when interacting with other plants than they do with members of their own species. Some plants have photoreceptors enabling them to detect certain red light profiles of others. Plants got eyes!

Anticipatory behaviour.

It is suggested that plants are constantly monitoring the environment to guess what the world is like. Some plants have been shown to make predictive decisions about the position of the sun or location of nutrients.

Learning and memory.

Plants may be able to learn from past experience and adjust behaviours accordingly.

Nervous system.

Even though plants do not have neurons or a nervous system as we recognise it, they do have neurotransmitters (such as acetylcholine, glutamate, dopamine, histamine, noradrenaline, serotonin etc). They also produce a communication system of electrical signals that travel along vascular conduits via a complex network of bundles of phloem, xylem and cambium.
Plants also react to anaesthetic agents with decreased responsiveness and electrical signal inhibition.

While the authors warn that further good research is needed before we go ascribing states of consciousness to our houseplants, they also encourage us to keep an open mind:

even if we cannot rule out the possibility that consciousness emerges from the activity of a sophisticated nervous system, we have no scientific or empirical reasons to exclude the possibility that other forms of life have evolved different structures for subjective awareness. Hence, even if we agree that ascribing sentience to plants may be too premature, inasmuch as there is no consensus on what biological features are required for consciousness, concluding that plants do not have it because they lack brains is a matter of presumption and begs the very question we are trying to address.

Dive deeper and read the full article here: Consciousness and cognition in plants

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Main photo:  cleo stracuzza