From the Editor: Top Crop West November 2016
Amid the day-to-day hustle of checking weather forecasts for some much-needed rain (or, depending on the year, sun), applying just the right nutrients to a field, and scouting for problematic pests, weeds and diseases, it’s easy to lose sight of a simple fact: plants have an amazing ability to adapt and survive.
This trait can be unfortunate in unwanted plants, such as kochia or Canada fleabane, which can develop resistance to an important herbicide such as glyphosate, but it can also bring important benefits.
Researchers at the United Kingdom’s University of Southampton found plants are adapting to increasing levels of carbon dioxide (CO2) in the atmosphere. Gail Taylor, a professor with the biological sciences department and lead author of a report in the journal Global Change Biology, compared two types of plantago lanceolata plants. The first type, found near CO2 springs in Bossoleto, Italy, consisted of plants that have been exposed to high levels of naturally occurring carbon dioxide for centuries. The second type were grown at a control site nearby and exposed to lower levels of CO2 currently found in the atmosphere.
In a news release, Taylor explained, “The study shows that when we take plants from these two places that represent the atmosphere of today with that of the future (out to 2100), and place them together in the same environment, the plants from spring sites were bigger and had a better rate of photosynthesis. Most importantly, plants from the spring sites had differences in the expression of hundreds of genes. In particular, we predict from these gene expression data that planetary greening will continue – it won’t switch off or become acclimated as CO2 continues to rise, but some of the extra carbon in future plants is likely to go into secondary chemicals for plant defense. This is associated with more gene expression underpinning plant respiration.”
Taylor concludes plants will adapt to rising CO2 levels in “unpredictable” ways, raising an important question for agriculture: how will food crops evolve?
One researcher at the University of Illinois has some ideas. Andrew Leakey, a plant biology professor, led an eight-year study of soybeans grown outdoors in a CO2 rich environment similar to that expected by 2050. The results are a mixed bag for producers. The study, published in the journal Nature Plants, found that under ideal growing conditions, higher CO2 concentrations boosted plant growth. However, drought, which is expected to become more common thanks to a warmer climate and shifting rainfall patterns, seems to counter those benefits and reduce yield.
Leakey and his team found plants grown under hot, dry conditions with higher levels of CO2 used more water than those grown under current CO2 conditions. This runs counter to other research, which suggests plants exposed to high levels of CO2 will shrink the pores in their leaves, cutting back on both the exchange of gasses with the atmosphere and the amount of water they draw from the soil.
“What we think is happening is that early in the growing season, when the plant has enough water, it’s able to photosynthesize more as a result of the higher CO2 levels. It’s got more sugars to play with, it grows more, it creates all this extra leaf area,” Leakey said in a press release. “But when it gets dry, the plant has overextended itself, so later in the season it’s now using more water.”
The plant also seems to become more sensitive to changes in the hormones that send signals between its roots and leaves, leading to less photosynthesis under drought conditions.
Both studies offer important insights into the challenges agriculture will need to overcome going forward. Like plants, producers must continue to evolve if they are to thrive and grow.
We hope this issue of Top Crop Manager will help you do just that.