The New Gastronome
Power of Plants
by Matilde Garzotti
by Matilde Garzotti
“Plants are nature’s alchemists, experts at transforming water, soil, and sunlight into an array of precious substances, many of them beyond the ability of human beings to conceive, much less manufacture. While we were nailing down consciousness and learning to walk on two feet, they were, by the same process of natural selection, inventing photosynthesis (the astonishing trick of converting sunlight into food) and perfecting organic chemistry. As it turns out, many of the plants’ discoveries in chemistry and physics have served us well. From plants come chemical compounds that nourish and heal and poison and delight the senses, others that rouse and put to sleep and intoxicate, and a few with the astounding power to alter consciousness – even to plant dreams in the brains of awake humans (Micheal Pollan, The Botany of Desire).”
Photosynthesis is, indeed, an important and indispensable event for the existence of our planet. Through it, carbon becomes life, and oxygen becomes available – chemically using the sun’s energy. The availability of oxygen, in turn, has shaped our atmosphere, as the accessibility of complex organic substances has forced the development of trophic chains, organised by levels of complexity, among living beings. At the base of these energy flows, we have the primary producers – autotrophs – on which the consumers – heterotrophs, once again organised in the hierarchical levels of detritivores, herbivores, carnivores, etc. – depend. Without primary producers, consumers would not exist.
Plants are the most widespread autotrophic organisms on earth, representing 85% of its biomass. They colonised the planet by creating deep and complex relationships with the surrounding environment and by fighting enemies despite lacking the ability to move actively. They respond to stimuli and communicate despite a lack of sight and hearing. Yet, somehow, they perceive the duration of day and night, temperature, gravity, humidity, pressure, the presence of nutrients and toxic substances, of competitors, predators and parasites.
The ability of plants to interpret the environment and to develop strategies and synergies is the result of a complex evolutionary story and versatile and creative adaptability, thanks to which plants are now able to determine processes and offer goods and services that, directly or indirectly, guarantee the survival of all living beings. Thus, they are also satisfying the needs of man through ecosystem services. There is, in fact, a strong dependence on plants for the basic needs of our daily life and even our economic-industrial development, which has played a fundamental role in the cultural evolution of human society.
Plants are autotrophic organisms. The word, deriving from Greek autotrophos, 丟ὐ件ός “self” and 件伏έϕ企 “nourish”, means supplying one’s own food, which plants do using their greatest evolutionary achievement: photosynthesis, the only biologically important process that allows direct use of solar energy.
Although very simple compared to plants, the first photosynthetic organisms were already much more complex than primitive heterotrophs. In fact, the use of solar energy required a complex system of pigments to capture the energy of light and to conserve that energy in an organic molecule. With the arrival of autotrophs, the flow of energy in the biosphere – the set of living organisms and the environment in which they live – began to take on its present form: the radiant energy emitted by the sun was conveyed through the photosynthetic autotrophs to all other forms of life. It didn’t take long for photosynthetic organisms to increase in number and change the appearance of our planet by making life as we know it possible.
This biological revolution occurred because one of the most efficient photosynthesis strategies involves the breakdown of the water molecule and the consequent release of the oxygen contained in it. Therefore, the quantity of gaseous oxygen in the atmosphere increased progressively. This had two important consequences: the first being that a part of the oxygen of the atmosphere’s outermost layer was converted into ozone, which can absorb ultraviolet radiation when present in sufficient quantities, thus making it possible to survive on the surface of water and land. Secondly, the increase in free oxygen opened a new path for more efficient use of the organic molecules rich in energy produced by photosynthesis. Indeed, many organisms acquired the ability to break down these organic molecules through a process that uses oxygen, known as respiration.
In practice, this means that without the evolution of these primitive autotrophs, life on earth would have soon come to an end.
Evolution of Communities: Biomes and Ecosystems
The conquest of land by plants has profoundly changed the appearance of the continents, as plants are, in a broad sense, the earth itself.
Rainforest, savanna, steppe, woodland, tundra, amazon: each of these words brings to mind a landscape. The main features of each landscape are made up of its plants, which in an imaginary tropical forest would surround us like a large dark-green cathedral; in a meadow, they would cover the ground beneath our feet; in the prairie, they would move in big golden waves.
Only when we have described these biomes – large climate-controlled natural communities characterised by specific groups of plants and animals – in terms of trees, shrubs, and herbaceous plants – will we be able to complete our landscape with other characteristics like a deer, a tropical bird or a snake. The plant and animal communities, together with their environment, constitute the ecosystem, a sort of communal entity made up of transitory organisms. Some parts of the ecosystem, the largest trees, can live for several thousand years, while others, like microorganisms, live only a few hours or even a few minutes. The ecosystem itself, however, tends to be very stable as it will try to remain in balance. Although many of the organisms of an ecosystem compete with each other for the same resources, the ecosystem functions as an integrated entity: all living beings, including the smallest fungal spores and bacterial cells, constitute a source of food, and, therefore, of energy, for some other organism. In this way, the energy captured by green plants flows neatly through a large number of organisms before being dissipated.
Moreover, the interactions between organisms as well as between them and the environment generate a regular cycle of essential elements. While the ecosystem must constantly supply the energy, the elements passing through the organisms are returned to the soil and, by the action of decomposing fungi and bacteria, return into the cycle. These transfers of energy and elements imply a complex succession of events in which each group of organisms plays a particular and specific role. Consequently, it is impossible to change even a single element within an ecosystem without risking the destruction of the balance on which its stability depends.
Plants, algae and photosynthetic bacteria are responsible for the productivity of all ecosystems, as they are the only organisms capable of capturing solar energy and manufacturing the organic molecules necessary for their life and that of other organisms. There are about 500,000 species of organisms capable of photosynthesis and an eight to ten times greater number of heterotrophic organisms completely dependent on them – including us.
Plants as Food
As paradoxical as it might seem, the consequence of the plant’s fixity is them being incredibly creative and intelligent from an evolutionary point of view – with intelligence understood as a general ability to solve problems. As animals equipped with a mobile body, we use our intelligence to move away from problems: if it is hot, we move towards cooler areas; if it rains, we seek shelter; if danger looms, we do everything to avoid it. But how do stationary plants do it? In the course of evolution, they compensated for their fixity with an incredible ability for chemical synthesis. Plants, thus, turn into alchemists capable of producing a myriad of warning signals with intense, sometimes poisonous, odours and flavours in order to discourage other organisms from attacking them. Among the various chemical weapons, there are toxic and bitter alkaloids such as caffeine in coffee or solanine in eggplant; the cyanide contained in cassava or in apricot seeds; irritating compounds such as capsaicin in chillies or alliinase in onions; substances that interfere with digestion such as tannins, polyphenols that inhibit digestive enzymes; essential oils and aromatic substances.
Plants have spread their functions to all their cells, thus making it possible to remove up to 80-90% of their organisation without destroying the plant’s life. For us, the idea of being eaten is a nightmare, while plants have evolved to withstand just that. In fact, when 20-30% of it is eaten by an animal, the plant does not activate its defence mechanisms since, from an energy point of view, it would be more expensive than simply rebuilding the part that was eaten. If, instead, 20% of an animal’s body were removed, it would certainly limit its chances of survival, as different bodily functions are concentrated in specialised organs. And so, the diffuse system developed by plants turns out to be an antidote to fragility.
“While the ecosystem must constantly supply the energy, the elements passing through the organisms are returned to the soil and, by the action of decomposing fungi and bacteria, return into the cycle.”
In order for plants to communicate and reproduce, they need to circumvent immobility by relying on mobile go-betweens like wind or animals. To encourage animals to help them out, plants created flowers, whose shape, colour and scent are designed to attract a particular insect that, flying around and collecting nutritious nectar or pollen for food, spreads the pollen from one plant to another, ensuring fertilisation. To avoid competition and overshadowing, successful plant families developed ways to disperse their seed far and wide, including seed containers, appendages and structures. Fruits are actually plant organs with the function of attracting animals through their colours, scents and textures, in order to be eaten and for the seed to be carried away.
According to the “State of the World’s Plant” report of the Kew Royal Botanical Gardens, there are an estimated 391,000 plant species known to science, of which 369,000 are flowering plants. Around 30,000 of these have a documented usage. At least 7,039 are edible plant species, but only 417 are considered food crops, of which just over 200 have economic significance.
Another Form of Preservation
Defined as ‘the multiple benefits provided by ecosystems to mankind’, ecosystem services include functions essential for the life of mankind that are supportive (soil formations, nutrient cycle, organic energy production, …), that supply (drinking water, fibres, wood, …), that regulate (the climate, tides, water purification, control of pathogens, …) and that are cultural (aesthetic, recreational, spiritual, …). Plants are the engines of ecosystem services, as they are the primary producers of an admirable combination of aesthetic value and ecological indispensability. They play an essential role in the biosphere, regulating the balance of important phenomena underlying life with their own energy processes.
But, putting man as the focus is not the right way to preserve its survival as it loses sight of the network to which it belongs and on which it is directly dependent. Man has arrived relatively recently in the world of the living. If we reduced the earth’s entire history to a period of 24 hours, at dawn, we would see the first cells appear; in the late evening, the first multicellular organisms. Man, instead, would make his appearance less than 20 seconds before midnight.
However, much more than any other animal, we have modified the planet’s surface by shaping the biosphere according to our own needs, ambitions and follies. We represent 0.01% of the earth’s biomass, and yet we believe that intelligence is the result of our brain and that the rest of the earthlings are organic machines that respond automatically to the environment. For us, life is a collection field that is there to be used. We have a predatory approach to any resource on the planet, which is absurd in terms of sustainability, especially if we consider that our world is an island. Instead, we should imitate the concept of the cooperative plant communities: communities based on mutual support as a factor of evolution, in which the community would become more and more important, especially if there were a survival problem. This, because the community is the environment and must be preserved as such; this, because it is home.
Photos @Aarón Gómez Figueroa