Investigating the impact of rising carbon dioxide levels on maize

JOURNAL HIGHLIGHTS BY STEVE RANGER

The rising concentration of atmospheric carbon dioxide (CO₂) is a major driver of climate change, with levels increasing from 280 parts per million (ppm) before the industrial revolution to 430ppm currently – with projections that it could reach 800ppm by 2100.

The increase in atmospheric CO₂ is likely to have a significant impact on agriculture, affecting plant physiology, photosynthesis – and productivity.

Now a team of international researchers has examined how maize responded to three levels of elevated CO₂ at three growth stages. The paper was published in SCI’s Journal of the Science of Food and Agriculture.

Higher levels of CO₂ enhance carbon assimilation, energy storage and biomass production, and also increases photosynthesis. But elevated CO₂ can also reduce phytohormone and phytochemical production, potentially weakening plants defenses against biotic stresses.

Maize is a key crop, vital for food as well as other uses such as for ethanol and starch production. But it is also highly susceptible to climate instability. ‘Understanding maize’s response to elevated CO₂ is critical for mitigating climate change impacts and ensuring food security,’ the researchers said.

The team investigated the impacts of elevated CO₂ on maize through a series of experiments. Maize seeds were grown under three CO₂ levels: 600, 1200 and 1800ppm,  using open-topped chambers.

The levels of CO₂ in the chambers was increased between 0830 and 1800 by releasing CO₂ gas from cylinders positioned around the chamber perimeter: the CO₂ was added only during daylight hours because plants do not respond to elevated CO₂ levels in the absence of light.

Two maize lines were used in the research and plants were harvested at three developmental stages: the vegetative stage at 40 days after sowing (DAS), tasseling stage (70 days) and dent stage (90 days).

The researchers found that the increasing levels of CO₂ had varying impacts on how the maize plants developed. They said the findings highlight the complex interactions between elevated CO₂ and plant metabolic processes, ‘offering insight into genetic and physiological mechanisms that could inform future crop management under changing atmospheric conditions’.

For example, both maize lines saw increased height and biomass at 600 ppm, with growth declining at 1800 ppm, particularly at 70 days after sowing.

Elevated CO₂ at 600 ppm enhanced starch, soluble sugars and total non-structural carbohydrate for both genotypes, but these components declined at the higher level of carbon dioxide.

Chlorophyll and carotenoid levels decreased under elevated CO₂, with C01 showing more pronounced reductions. Folate content peaked at 70 DAS for both genotypes, the researchers said, while lignin content was inversely proportional to CO₂ levels, with significant reductions at 1800 ppm.

The researchers said future research should explore the molecular mechanisms driving these genotype-specific responses, particularly in lignin and folate biosynthesis, as well as investigate the impact of elevated CO₂ on other biochemical pathways.

‘Long-term field studies under varying CO₂ levels are needed to assess how climate change may affect maize productivity and nutritional content. Breeding strategies targeting enhanced growth and stress resilience under elevated CO₂ should also be prioritised,’ they said.

The influence of rising carbon dioxide on maize development: genotypic differences in growth, lignification and folate pathway
Pirzada Khan, Sajjad Asaf, Lubna, Eman R Elsharkawy, Rahmatullah Jan, Kyung Min Kim
Journal of the Science of Food and Agriculture
doi.org/10.1002/jsfa.70251