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You Say Potato...

By Robert C. Balling Jr., Ph.D.
Arizona State University

Last issue, we delighted vegetables and those who love them with the news that increased levels of atmospheric carbon dioxide (CO2) would provide tremendous benefits to the growth and production of carrots and radishes.

Now, recognizing that that those crunchy treats are only warm-ups to a healthy meal, we turn our attention to more robust fare, peas and potatoes. Once again, a literature search on CO2’s effects confirms that the future is fertile for these important crops.

For example, Paez and colleagues grew pea plants in controlled environment growth chambers under varying conditions; some were well-watered, maintaining CO2 levels at 350 parts per million (ppm), which approximates our current level of 360 ppm; others were well-watered and grown at CO2 levels of 675 ppm.

Other peas were grown at those same levels of CO2, but were exposed to drought stress. As Figure 1 shows, the well-watered plants reaped some benefit from the elevated CO2, but the plants exposed to the drought stress realized an even greater enhancement from the elevated CO2.

Figure 1 (3331 bytes)

Figure 1. Doubling atmospheric CO2 enhances both well-watered (cross-hatched) and drought-stressed (solid) pea plants.

But the real story emerges from the measurements of the peas themselves. For the well-watered plants, the fruit dry weight of the peas rocketed upward by 127 percent for the near doubling of CO2. Add water and CO2, and the plants more than doubled their productivity!

The recipe for potatoes and CO2 deserves honorable mention as well. Bhattacharya and colleagues grew sweet potatoes in open-top field chambers with ambient and doubled CO2 conditions (364 ppm vs. 666 ppm). Like Paez, they propagated both well-watered and water-stressed plants.

Figure 2 shows that for well-watered plants, the all-important root weight increased by 40.3 percent in response to elevated CO2. The water-stressed plants experienced a 5 percent root enhancement in the elevated CO2 chambers. In both cases, the starch level increased due to the higher CO2 levels. The authors concluded, "CO2 enrichment resulted in increase of sweet potato root–shoot ratio, yield of fresh storage root, and storage root starch even under water stress conditions."

Figure 2 (3112 bytes)

Figure 2. Doubling atmospheric CO2 also enhances the growth of well-watered sweet potato plants.

If you’re not keen on sweet potatoes, consider the recent findings of the Miglietta team, who grew white potatoes at various elevated levels of CO2 and measured photosynthesis, biomass, and crop yield. Among other findings, the authors concluded that a doubling of CO2 (ambient vs. 660 ppm) produced a 40 percent increase in potato yield. Furthermore, the plants flowered earlier and the yield was realized more quickly for the elevated CO2 condition.

We are entering an age of abundance. Carrots, radishes, potatoes, and peas will all grow much better as the CO2 of the atmosphere continues to rise. And we will no doubt eat much better as a result.

References:

Bhattacharya, N.C., et al., 1990, Interaction of enriched CO2 and water stress on the physiology of and biomass production in sweet potato grown in open-top chambers. Plant, Cell and Environment, 13, 933–940.

Miglietta, F., et al., 1998, Free air CO2 enrichment of potato (Solanum tuberosum L.): Development, growth and yield. Global Change Biology, 4, 163–172.

Paez, A., et al., 1983, CO2 enrichment, drought stress and growth of Alaska pea plants (Pisum sativum). Physiologia Plantarum, 58, 161–165.