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Celebrate the power of plants

Its unique orbit within the ‘Goldilocks zone’ renders planet Earth habitable. For over 450 million years the unique ability of plants, from microscopic algae to mighty Sequoias, to harvest sunlight and change carbon dioxide and water into sugar while releasing oxygen has created a habitable world for millions of animal species, including ourselves. Without the ‘Cinderella of science’ — the boring botany bit (Willis 2014) — life as we know it would not have been possible.

Ever since they first appeared, plants have littered the earth with evidence of their presence (one of the few attributes they share with humans). Then, through geological processes, fragments of this litter have been preserved in the rock record. Reading the palaeobotanical evidence begins with rigorous yet painstaking observation, identification, interpretation, and classification. A necessary step since all subsequent research depends on these fundamental conclusions, but challenging given its subjective nature. Plants, being organic entities, do not always fit neatly into classification schemes, thus complicating and challenging our preconceptions. But embrace this challenge and ‘boring botany’ can provide insights into probable continental connections, vegetation zonations, climate, and the evolution of biochemical pathways. Perhaps not so boring after all!

Let’s take a simple example. Trees have evolved over millions of years adapting to their environment, modifying their physical shape and internal functioning to maximize success and cope with competition. We can make observations on several scales:

• Macro-characters disclose form, habit, stature, and support;
• Meso-characters reveal shapes and sizes of flowers and leaves, as well as visible protective strategies;
• Micro-characters testify to reproductive strategies, stomatal responses, and chemical makeup.

Now look at the fossil record. Local vegetation can be derived directly from identifying wood, whose role is support not dispersal. Contrast this with leaves and their greater ability to disperse into the wider depositional setting. Pollen (or spores in the cryptogams) and seeds evolved for dispersal over long distances and therefore evidence a regional flora. When we compare these assemblages across continents, we start to understand past ecosystems and biomes.

The interaction between plant and environment is inherently interlinked. Fossilized plant parts act as proxies for environmental factors (Poole & van Bergen 2006):

• Growth rings record the relative favourability of the habitat, length of growing season, forest productivity, and insect infestation.
• Leaf cuticle thickness relates to aridity.
• Leaf size shows climate type.
• Stomata indicate relative deep-time pCO₂.
• Carbon and oxygen atoms in ligno-cellulose compounds record past atmospheric changes.

So one fossilized tree can provide numerous signals pertaining to both the local and regional environment. Extrapolate this to all plant parts and taxa, and the potential is enormous.

Yet obstacles, like Cinderella’s stepsisters, stand in the way. Trends in society drive funding initiatives, which determine the direction of scientific research. The ever-increasing demand to find a quick fix shouldn’t impede rigorous data gathering and analysis. Data sets need to be as large as possible, allowing plant taxa (beginning at the species level) to be traced back through geological time.

Base lines need to be anchored in modern plant science and systematics. Duly acknowledging inherent uncertainty and alternative interpretations, and accepting that past plants and environments may have no modern analog, ensures robust and rigorous extrapolations from like-with-like character comparisons. Let’s embrace what we find, accept that the natural world is more inventive than we often suppose, and invest time and money building solid foundations for future developments.

The Cinderella of science is ready for her unveiling. Let’s celebrate her contribution to our Goldilocks world by giving her the accolades she deserves.


References
Poole, I and P van Bergen (2006). Physiognomic and chemical characters in wood as palaeoclimate proxies. Plant Ecology. 182, 175–195.
Willis, K (2014). Plants: From Roots to Riches: Radio 4 airs epic series on plants. The Independent. Available at ageo.co/1svst1O

In praise of paper and pencil

Leonardo was a geophysicist

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