Can plants fast forward to the future to show us what will happen as carbon dioxide in the atmosphere increases?

A new analysis suggests that long-term, multi-generational response of plants to rising CO2 are similar to those found in single generation FACE experiments, with consequences for continued global greening and future higher rates of photosynthesis.

Time-travelling plants that could move forward and backwards across the decades would be extremely valuable in understanding how these photosynthesizing organisms are likely to respond to the altered conditions predicted as a consequence of anthropogenic climate change.

One aspect of this change in climate is irrefutable – the steady rise in atmospheric carbon dioxide that has occurred since the onset of the industrial revolution. Even now, CO2 is at the highest concentration the earth has seen for more than several million years. This is critically important for plant life on earth because the process of photosynthesis uses this CO2 and along with sunlight, turns it into simple sugars and complex carbohydrates. Scientists have been investigating how plants will respond to future increasing atmospheric CO2 using special facilities where fields are blasted with air that contains increased amounts of carbon dioxide – called Free Air CO2 Enrichment (FACE) experiments and many experiments have been completed to determine plant response to these future conditions.

One problem with this approach, though is that ‘todays’ plants are exposed to these future conditions, they time travel as seeds produced in today’s conditions and their responses may not, therefore, be representative since they have not been subjected to the CO2 conditions of the future for multiple generations allowing to for them to adapt, through genetic changes to these new conditions. Many of these time-travelling single generation experiments have been conducted and have revealed a consistent set of responses – more photosynthesis, more growth, less concentrated leaf nitrogen and more sugar and starch (see below).

Natural high CO2 springs across the world
Natural high CO2 springs across the world and here where 39 species were studied at 11 spring sites.
Responses to higher CO2
Response to CO2 for spring and FACE grown plants.

In a new meta-analysis, Saban et al. took a different approach and assessed all of the data collected for plant response to high CO2 concentration from plants grown for multiple generations over many decades in naturally high CO2 springs. Such springs are found across the world – with 23 highlighted here- and many have been the focus of studies on the physiological responses of plants to rising CO2, similar to those undertaken in FACE experiment. Comparing these two approaches, plants subjected to higher CO2 against plant lineages that have had time to acclimate, has never been done before.

High CO2 springs harbour a vast array of plant types and in contrast to FACE, provide critical insight into the decadal, long-term response of plants such as those likely to occur in future, where multiple generations ensure that time-travelling seed sources are no longer an issue. Remarkably, the analysis shows that many of the responses for spring plants are similar to those observed in FACE experiments. This gives us confidence that plants are likely to keep responding positively to rising CO2. They will not become acclimated and the increased global greening that is currently happening across the world, 80% of which is attributed to rising CO2 is likely to continue. If no other climatic factors are limiting, crop yield is likely to be stimulated too, but this may be held in check by limitations in rainfall for some area of the world, at least.

The study suggests that the single generation response may adequately predict the multigenerational response. This means that it’s possible to test new varieties of plant in FACE experiments, before it is critical that they perform in the wider world. Likewise, studies of genetic changes and production of proteins can be found before they’re out in the wild. It means to that we can, in a way, send plants ahead to the future and get hints of what it might look like.

Reference List

Saban J.M., Chapman M.A., Taylor G. (2018) FACE facts hold for multiple generations; Evidence from natural CO2 springs. Global Change Biology