The Web of Life (68) Plant Intelligence

Intelligence

Plant behaviour is active, purposeful, and intentional. The plant gathers information about its surroundings, combines this with internal information about its internal state and makes decisions that reconcile its well-being with its environment. ~ Anthony Trewavas

Intelligence is demonstrated by behaviors. Plants are so different from animals that is it commonly thought that plants do not behave at all.

Animals skitter about, bodies and limbs in motion, their communications in sounds, gestures, postures, and expressions. Chemical processes within proceed largely outside animal awareness and control. Decisions regularly take place unconsciously, only coming to awareness in their fruition.

In contrast, phenotypic plasticity and chemical production predominate plant behavior. Plant gestures and expressions are unrecognizable to us.

Plants use microfluidics and optics to move, change color, and pump water. ~ Greek American electrical engineer Demetri Psaltis

Visible plant actions largely comprise growing and discarding parts. Production and allocation of chemical resources is crucial plant behavior.

Plants intake and integrate information from among their various parts, combine it with remembered and genomically available knowledge, and intelligently make decisions. Because plant behavior is largely chemical and phenotypic, the number of choices that a plant at any moment has dwarfs any analogue of animal behavioral options.

Plants live a life of conscious chemistry. Their thoughts and behaviors are exercises of molecular awareness. The contrast to animals is incomparable.

The genomes of DNA-containing cell organelles (mitochondria, chloroplasts) can be laterally transmitted between organisms, a process known as organelle capture. Organelle capture occurs in plants. ~ Belgian biochemist Sandra Stegemann et al

As molecular mavens, plants comprehend the meaning of the informational codes behind genetics. They examine all the DNA that comes to them – whether bacterial, fungal, animal, or from another plant – to determine whether it may have value. This partly explains their ability to establish and regulate relations with other life forms.

Plants control their own genetic destiny: manipulating their genome in a vast variety of ways to achieve goals.

Part of identity is what you aren’t. Especially for plants because they are so changeable and susceptible to environmental conditions, the part of the genome that is not needed, or that might be providing exactly the wrong information, needs to be shut off reliably in each condition. This information is then passed on to daughter cells. ~ American microbiologist Doris Wagner

Deciding priorities and energy allocations is so complex that no plant behavior is autonomic. Unlike animals, there is no plant unconscious.

One aspect of existence that is the same for both plants and animals is memory. Plants remember their ecological interactions and derive meaning from them. Plants have long-term memory.

Animals process memories when they sleep. Plants rest during the night, but it is not known whether this helps them incorporate memories.

As with animals, the lessons that traumas may teach need to be learned, but the emotional impact of traumas must be set aside if a plant is to recover and lead a healthy life.

Stress memories may be maladaptive, hindering recovery and affecting development and potential yield. In some circumstances, it may be advantageous for plants to learn to forget. ~ Australian botanist Peter Crisp et al

Animal emotions play critical roles in memory retention, judgment, and motivation. Evidence of plant emotions is anecdotal, but the evolutionary advantage of emotions is such that it is hard to imagine that plants lack emotive feelings. Plants demonstrable will to live suggests there being an emotional context to their behaviors.

◊ ◊ ◊

Plants plan. Decisions about growth or defense are processes of potentiality, aimed at meeting anticipated needs.

Plants anticipate attacks from insects in much the same way that they anticipate the sunrise. ~ American biologist Michael Covington

Assessing the far-red radiation coming off the leaves of competitors, plants can predict potential loss of light in the foreseeable future. One intentional response is shade avoidance – a goal-oriented behavior.

There is an extensive spread of prerain green-up over Africa. ~ Nigerian terrestrial ecologist Tracy Adole et al

A swath of Sub-Saharan Africa has a rainy season with an attendant bloom of vegetation. Plants there anticipate rain coming and green up before the rain arrives. They also know when the rainy season ends and lose their lushness just after the rain stops, thereby conserving their resources.

Associative learning is an essential plant behaviour. ~ Australian biologist Monica Gagliano et al

Experience and calculation of relative gain determine decisions in plants just as they do in animals. Plants constantly assess the probabilities of favorable outcomes given an ample array of possibilities for root and shoot growth vis-à-vis defensive measures. Plants take risks when they feel they need to.

Competition plays a fundamental role in plant ecology. Plants evolved both the ability to detect the presence of neighbours and to plastically adjust their phenotypes in response. Plants can respond to light competition in 3 strategies, comprising vertical growth, which promotes competitive dominance; shade tolerance, which maximises performance under shade; or lateral growth, which offers avoidance of competition. Plants choose according to outcome. Plants adopt optimal scenarios. ~ German botanist Michal Gruntman et al

 Pesky Pollinator

The coyote tobacco prefers to rely upon the hawkmoth for pollination, as the moth visits many plants in its wide-ranging forays. The problem is that the hawkmoth is both pollinator and pest: it lays its eggs on the plant, and its larvae love eating tobacco leaves. Those plants which best reward hawkmoths with nectar are most likely to have eggs laid on them; a cruel irony indeed.

The coyote tobacco courts the nocturnal hawkmoth by opening its flowers at sunset and wafting an alluring scent. This benevolence shuts down when hawkmoth larvae (tobacco hornworms) make tobacco leaves their meal ticket. The plant produces specific pesticides which decrease the caterpillars’ digestive ability.

As a final gesture of disgust, the plant stops flowering in the evening and opens for business at dawn, thereby attracting hummingbirds. Hummingbirds may not be as prolific a pollinator as hawkmoths, but at least they don’t eat you alive. Once a coyote tobacco is no longer losing leaves to hornworms the plant goes back to preferring hawkmoths as their pollinating pals.

 Killer Quorum Mimic

To have any chance of success, bacteria attack plants en masse. Little pathogens determine that they have the numbers on their side via chemical quorum-sensing communications.

Plants understand quite well how bacteria operate. To thwart a mass assault, plants concoct and release chemicals that mimic those used by bacteria to signal each other that the time to attack has come.

A plant fires off its molecular mimic before bacteria have sufficient numbers to tackle their target. The microbes invade before they have enough troops, whereupon the plant picks them off.

○○○

Typically, only 1–3% of light absorbed by a flowering plant is converted to chemical energy, though it may run as high as 8%, as in sugar cane. Much of the solar energy instead goes to heating and pumping water. The reason is that plants practice a form of endothermy: keeping leaves at 21.4 °C, which is optimal for photosynthesis. Trees ranging from Alaska to Mexico keep their leaves at the ideal temperature.

Plants have sophisticated strategies to secure resources. Nitrogen is exemplary of supplies that are heterogeneously distributed in the environment. If a root senses a local shortage pending, it consults with a shoot that it services, which may suggest lateral root growth toward regions that promise better nitrate uptake.

Plants integrate local and global nutrient cues to spend resources efficiently. ~ Dutch botanists Ton Bisseling & Ben Scheres

While some determinations are made that affect a whole plant, many are local, especially in a relatively mature plant with more resources at its disposal. Plant intelligence is therefore a fluid mix of holistic and decentralized decision-making.

An experienced root tip, having encountered a situation before, knows the best way to proceed. A poplar leaf, having been scarred by an insect thug, kicks into defensive emission faster than a naïve leaf.

 Barberry Battles Barbarism

The barberry is a European shrub that produces berries with 1 or 2 seeds; typically 2. The plant has the ability to halt the development of its berry seeds.

The parasitic fruit fly Rhagoletis meigenii punctures berries to lay its eggs inside. The barberry is aware of a berry being infested.

If one of the 2 seeds in a berry is infested, a barberry aborts the infested seed to save the uninfested one. But if the berry only has a single seed, the plant gambles that the larva may die, which is a possibility. After all, losing a 1-seed berry is an utter waste of fruit.

○○○

Photosynthesis during the day lets a plant grow and pack away enough energy to last the night. When the Sun goes down, based upon its starch storage, a plant precisely calculates, on a leaf-by-leaf basis, how much energy it can use until dawn.

Optimizing efficiency, each leaf allocates its resources over time via arithmetic division. Using its internal clock, a plant monitors its accuracy by repeated calculation during the night, adjusting as necessary.

If the starch store is used up too quickly, a plant starves and stop growing. Conversely, too-slow consumption is a waste. Plants get it right, but caution is applied. Leaves leave a 5% contingency reserve.

The computational capabilities of plants are enormous. Plants uses their genome as an active database, precisely manipulating their own epigenome for remembrance.

Flowering plants remember induced states for long durations via various mechanisms, including altering the chromatin at certain genetic loci, through self-reinforcing protein modifications, and cellular memory via stable developmental or metabolic states. These are just evidentiary artifacts to the vibrant energy system that lies behind all living matter.

Growth represents resource investment. The best return-on-investment is a choice that offers relative stability.

Plants consider context. Trees manage to grow in well-spaced patterns, as a walk through the woods readily shows. Various feedback mechanisms prevent overcrowding.

Plants learn and remember which specific growth patterns are most productive. Some plants with a natural propensity toward spindly growth get bushier when pruned. Having sensed that they are somehow spatially confined, plants adjust based upon experience.

Physically, memory meets action potential by electrical impulses, analogous to animal nervous systems. Ionic signals propagate through plants cells, provoking chemical changes that often incite physiological and morphological transformations.

There are thousands of interrelated states throughout a plant. Changes in states are coordinated.

Different plant stems have varying success with their leaves harvesting light. While bright light typically encourages growth in that direction, shoot growth is halted when heading into the shade.

A plant makes growth decisions based upon all the information available to it. To optimize nutrient harvest, data from individual roots are collated to determine an overall growth pattern for further root foraging.