Enlivening the barren leaves

Scientific investigation is often a reductive process involving precise experiments in artificial environments. Perhaps some advice from a romantic poet will help to avoid the pitfalls of too narrow a view of plant research.

Up! up! my Friend, and quit your books;

Or surely you'll grow double:

Up! up! my Friend, and clear your looks;

Why all this toil and trouble?

The sun above the mountain's head,

A freshening lustre mellow

Through all the long green fields has spread,

His first sweet evening yellow.

Books! ‘tis a dull and endless strife:

Come, hear the woodland linnet,

How sweet his music! on my life,

There's more of wisdom in it.

These are the opening verses of the poem ‘The Tables Turned’ by William Wordsworth, which was published in the collection Lyrical Ballads, with a Few Other Poems by Wordsworth and Samuel Taylor Coleridge in 1798. This collection was a minor event at the time but has since come to mark the beginning of the Romantic movement in poetry as it attempts to move away from the convoluted use of language that characterized poetry in the eighteenth century and to employ everyday words and phrases. ‘The Tables Turned’ is a little remembered poem compared with others in the volume, which includes Coleridge's ‘The Rime of the Ancient Mariner’ and Wordsworth's ‘Lines Composed a Few Miles above Tintern Abbey, On Revisiting the Banks of the Wye during a Tour, July 13, 1798’ (also known simply as ‘Tintern Abbey’) but it carries an argument that remains worth considering two centuries later.

In the poem Wordsworth rails against the dominance of book learning (‘barren leaves’) and suggests that his friend should ‘get out more’, asserting that useful knowledge is more readily acquired by the contemplation of nature in its natural setting than by reading what previous authorities might have written. Wordsworth was particularly concerned with lessons in moral philosophy but there are parallels to be drawn with scientific research. Put simply, there is much that can be learned from a reductionist approach observing model plants in controlled environments, but the real world is a complicated place and laboratory observations are not substitutes for observations in the field.

Nature Plants strives to maintain a balance between laboratory-based and field-based studies. For example, in this issue you will find a brace of papers looking at the movement of small RNA molecules between plants and invading pathogens^1,2, and the presentation of a new twist on the use of CRISPR for gene replacement and insertion³. But alongside these you will also find an analysis of 30 years of data showing how the progressively earlier onset of spring as a result of climate warming is increasing nitrogen limitation in North American forests⁴, and a meta-analysis of more than 80 studies looking at the interaction of native and invasive species, showing that following an initial invasion by a single species the way is cleared for subsequent alien species to invade more easily⁵.

An extremely elegant illustration of field and laboratory experiments not telling the same story emerged last year with the creation, by scientists working at Rothamsted Research in the UK, of a wheat variety genetically engineered to synthesize and release (E)-β-farnesene (Eβf), an alarm pheromone for many aphids⁶. This was an impressive feat of engineering involving multiple transgenes. Aphids were successfully repelled by the plant-produced pheromones and wasps parasitic on aphids spent more time hunting on transgenic plants. However initial field trials showed no differences between aphid infestation or parasitization of the aphids between the engineered and controlled crops.

This should not be regarded as a failure; rather it demonstrates that the natural environment is very different, even compared with the greenhouse. It may be that aphids became habituated to the constant production of the alarm signal — the wheat was ‘crying wolf’ — or air movements may have prevented the necessary accumulation of volatiles. But as Professor John Pickett, lead investigator on the project, said, “the field is the ultimate arbiter”⁷.

Perhaps the most audacious examples of experimental research ‘in the field’ are those studies that attempt to change the aspects of the local environment of plants in situ. Many of these are concerned with climate change and are sometimes collectively known as FACE experiments, even when this acronym (which stands for Free-Air CO₂ Enrichment) is not accurate as no manipulation of CO₂ is involved. Only last month Nature Plants published one such study looking at the effects of CO₂ changes and drought on soybean growth⁸. Within a field of soybean, specific areas were subjected to reduced rainfall by covering those plots with retractable awnings. Releasing CO₂ from sections of pipe surrounding the plots increased its levels, which required careful control to ensure that the section of pipe releasing the gas was always on the upwind side of the plots. We have also published a study assessing the effects of elevated levels of CO₂ and ozone on the degree of insect damage experienced in forest canopies⁹, again using a FACE approach.

Such interventions were certainly not what Wordsworth was thinking about when he was writing his verses or striding over the Quantock hills contemplating nature. Nevertheless, his call to achieve understanding by taking our studies away from the desk (or lab bench) and out into the natural world is as valid now as it has ever been.

Sweet is the lore which Nature brings;

Our meddling intellect

Mis-shapes the beauteous forms of things:—

We murder to dissect.

Enough of Science and of Art;

Close up those barren leaves;

Come forth, and bring with you a heart

That watches and receives.