Sunday , February 28 2021

Together, more heat and more carbon dioxide can not alter the amount or nutritional quality of the crops



Researchers around the world are trying to find ways to feed a growing population, which is estimated to reach almost 10 billion by 2050. But as humanity struggles to increase the yield of crops, Could it have a nutritional quality of crops?

Soybean seeds ready for harvest.
Project Claire Benjamin / RIPE

It is difficult to predict how crops will respond to future environmental conditions. Growing plants in greenhouses or quarters of growth allow researchers to create any environmental condition that can be imagined. But plants grown in this way are like caged animals; How they behave in these enclosures may not be predictive of how they behave in nature. This challenge can be overcome by means of the traditional agriculture coupling with experimental techniques to simulate the future growth conditions.

As biologists of plants, we focus a lot on understanding how crops respond to environmental changes and when determining the resulting composition of plant tissues. In our most recent study, the objective was to understand how future climatic conditions, such as higher carbon dioxide levels and warmer temperatures, influence the health and nutritional qualities of a crop important both for which refers to how much can be harvested and how much mineral nutrition changes, a kind of crop report for the future.

Heat and carbon dioxide

The process that allows plants to use sunlight to convert carbon dioxide to the air in sugars and stored fats – carbohydrates – which ultimately lead to growth is called photosynthesis. These carbohydrates end up in what the farmers collect. Plants also absorb soil minerals, which are critical for survival. These minerals also end up in the crop of food farmers. Therefore, plants are critical for human health, both in terms of calories from carbohydrates and minerals to our diets.

For several decades, studies have consistently shown that higher levels of carbon dioxide produce higher yields in most crops. However, there are very few field experiments in the real world about important crops that examine the impact of the increase in carbon dioxide and the warmer temperatures.

The first important results of our work showed that the experimental warming increased a different understanding of how plants can respond to a high carbon dioxide. This previous work was the first to demonstrate that yields decreased when crops were cultivated in futuristic conditions created to increase current temperatures by 6.3 degrees Celsius (3.5 degrees Celsius), regardless of whether plants are Cultivate at current levels of carbon dioxide or levels increased by 50 percent, which is planned for the year 2050.

Although performance is important, so is quality, which is a measure of concentration of mineral nutrition necessary to safeguard human health. Studies have already shown that the increase in carbon dioxide can endanger human nutrition by reducing the nutritional quality of many different crops. Again, our experiment showed that the increase in temperatures complicated the greatest history of carbon dioxide.

Growing plants at warmer temperatures gave rise to higher mineral nutritional quality, especially for two minerals that are critical for human health: zinc and iron. The hottest temperature results in less performance, but higher quality. On the contrary, high carbon dioxide results in more performance, but with a lower quality. The combination of high carbon dioxide and warming produces a yield and quality that match more or less what we see today.

The impact of the concentration of carbon dioxide and the temperature on crop performance and nutritional quality.
Carl Bernacchi, CC BY-SA

Creating future environments

Exploring how plants respond to global climate change is a challenge, especially if the goal is to avoid the "caged animals" effect of artificial enclosures. Much of the research that investigates the relationship between the growth of plants and the increase in carbon dioxide has been carried out in the facilities of Free Air Concentration Enrichment. These facilities are designed to check how plants in a wild state will respond to future carbon dioxide concentrations by adding pure carbon dioxide to the wind blowing a crop. Our research on high carbon dioxide and warming effects on nutritional quality are based on an outdoor concentration-enhancing experiment in the heart of the corn belt of the center of the city. 39; the west that used infrared heaters to make warm crops at temperatures expected in 2050 during the entire growing season.

The nutritional quality of the crop was not an original goal of research into the enrichment of outdoor concentration in future levels of carbon dioxide and temperature. A meeting of opportunities between us and the biochemist Steven Huber led us to analyze the elemental content of stored soybeans from the search for free-to-air concentration. We realized that the range of technical knowledge and a former postdoctoral researcher, Iris Köhler, specializing in plant physiology, could reveal an important problem that faces agriculture. The result: an understanding that two major factors of global change: carbon dioxide and temperature, are offset by both the quantity of performance and the quality.

A series of infrared heating installed on soybean crops throughout the growing season.
Carl Bernacchi / USDA-ARS
Aerial view of a high carbon dioxide (green octogon) plot with an infrared heating matrix (triangular structure) in the interior.
Carl Bernacchi / USDA-ARS

Mechanisms of change in crop nutrition

The reason for the changes in the concentration of minerals is less clear than the changes in performance. Because plants need carbon dioxide for photosynthesis, more carbon dioxide leads to more photosynthesis and more growth. This greater growth gives rise to higher yields in the fields of the farmer.

The highest temperature causes lower yields, but the reason is more complex than for high carbon dioxide. High temperature normally lowers photosynthesis that causes lower growth and lower performance. The high temperature also affects the reproductive organs of the plant, and reproductive organs are the ones who finally make the seeds that the farmers collect.

Higher levels of photosynthesis in high carbon dioxide can lead to more carbohydrates diluting mineral nutrients in seeds, which would lead to a lower concentration of minerals. Plants that grow in high carbon dioxide also use less water, and many minerals, such as iron and zinc, pass through the plant as the roots absorb water, which can lead to lower absorption of nutrients minerals This could also explain a lower concentration of minerals in the crop. Both, or both, these ideas could explain the results observed for plants grown with high carbon dioxide.

The same mechanisms can be applied with high temperature; We have observed a lower photosynthesis when the plants are grown at high temperature, which leads to the production of less carbohydrates. Therefore, the concentration of minerals in relation to carbohydrates would be higher. The plants that grow at a higher temperature also experienced a lower humidity, which causes that the plants use more water of the ground. This could also result directly in a higher mineral concentration of seeds. Whatever it is, or a completely different mechanism, or a completely different mechanism, is responsible for these observations, more research will be required.

Next steps

What can be done to understand the mechanism behind the compensation between temperature and carbon dioxide in the nutritional quality of the seeds?

The theory of nutrient absorption can be tested with an experiment that tries to control the use of plant water. If the nutritional quality of soy is dominated by the amount of water used by plants, after changing the level of carbon dioxide and / or temperature around a plant, maintaining a constant use of The water in all treatments should result in a constant nutritional quality.

We are building a prototype of an experimental system to control humidity in our facilities to test this hypothesis. If this hypothesis is not compatible, we must move on to the design of experiments to test the concept of nutrient dilution.

A precocious prototype of an air humidification system in the field. This initial version was too powerful and it is still necessary to refine once the northwestern United States defrosts.

This work focuses on a crop in one place and if this response is restricted to soy, or applicable to other crops, it will also require an additional study.

There are far fewer global-scale concentration-raising facilities that there are crop species, and even fewer air-enrichment enrichment facilities Free to implement heating capacities in the field. However, the importance of maintaining a safe food supply that meets the nutritional demands will ensure that the largest scientific community, including, continues to investigate this area.


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