June 21, 2010

Spinach Lovers Rejoice

Filed under: Adaptation, Agriculture, Plants

We at World Climate Report wholeheartedly endorse First Lady Michelle Obama’s “Let’s Move” campaign to curb childhood obesity. As she has said many times, about two-thirds of American adults, and about a third of American children, are overweight or obese. The country spends $150 billion every year treating obesity-related diseases, most of which are preventable. Military officials, looking at a pool of increasingly overweight recruits, have said that the nation’s weight problem is a security issue as well as an economic one—obesity is now one of the most common disqualifiers for military service.

If you are in the DC area, be sure to make a visit to the south lawn of the White House grounds where the first lady will be organically growing lots and lots of spinach (more spinach than anything else—see Figure 1)! She not only plans on growing the stuff, but she is featuring her side dish called “No Cream Creamed Spinach” which to feed six people requires two pounds of baby spinach (the recipe is at the end of our article). We are sure the Obama children just cannot get enough of her healthy spinach salad.


Figure 1. Layout of the White House vegetable garden. Note the preponderance of spinach!

Given the Obama’s focus on spinach, we decided to deliver them some wonderful news about how spinach responds to elevated levels of atmospheric carbon dioxide (CO2).

The first article we found appeared recently in the Annals of Applied Biology and was produced by five scientists with affiliations with various institutions in China and Australia. Jin et al. reveal that “This research was financially supported by the State Key Development Programme for Basic Research of China, the Natural Science Foundation of China, and the Major Research Program of Zhejiang Province.” Apparently, China is onboard the spinach express and they are seriously funding research on our favorite leafy vegetable.

Jin et al. grew spinach in growth chambers with ambient levels of CO2 at 350 ppm and elevated CO2 at 800 ppm. Although not the focus of their research, they report results on how spinach was impacted by the higher levels of CO2. After 20 days, the elevated CO2 had caused the shoot fresh weight to increase by 75% while the shoot dry weight increased by 50%. The picture below shows both the control plants on the left side and the elevated CO2 plants second from the right side—the control plants look scrawny compared to the luckier ones that grew in a chamber with higher levels of CO2. Jin et al. also noted that the extra CO2 more than doubled the rate of photosynthesis by the plants, and if the news just couldn’t get any better for the first lady, the plants enjoying the extra CO2 increased their soluble protein levels by 33%!


Figure 2. The plants of spinach grown in soil for 20 days after nitric oxide (NO) and CO2 gas treatments (from Jin et al., 2009)

A second recent article on this subject appeared in Biologia Plantarum by four scientists with the Indian Agricultural Research Institute in New Dehli. Jain et al. grew spinach in open top chambers with ambient (350 ppm) and elevated (600 ppm) of CO2. At the end of the 80-day experiment, they made a series of measurements and found that leaf dry matter increased by 16%, stem dry matter increased by 12%, the leaf area increased by 7%, photosynthesis increased by 4%, stomatal conductance decreased by 5%, and calcium levels increased by 4%. In case you have forgotten your botany lessons, stomatal conductance is the speed at which water evaporates from pores in a plant, and is directly related to relative size of the stomatal pores. Basically, the higher the evaporation rate, the higher the conductance of the leaf. So not only did the plants grow larger, they did so using less water!

Don’t worry, research has been conducted here in the USA adding more glorious news about the future of spinach. The article is in Environmental and Experimental Botany and was written by four scientists with Northern Illinois University in DeKalb. Holbrook et al. grew spinach hydroponically in open top chambers with atmospheric CO2 levels maintained at near-ambient (400 ppm) and highly elevated (1,500 ppm) concentrations. After 21 days, they observed that the fresh weight of the plants more than doubled thanks to the elevated CO2. More importantly to spinach lovers, the specific fresh weight of the edible leaves (weight per unit area) increased by 40%.

Mrs. Obama’s husband has threatened to move on some “cap and trade” legislation to reduce the emissions of CO2 across this great country. But as we’ve seen in these three studies, higher levels of CO2 will produce larger plants, bigger leaves, higher rates of photosynthesis, and a greater level of water use efficiency. The beloved spinach in the White House garden is like virtually every member of the plant community—spinach loves higher levels of atmospheric CO2!

We hope that Michelle draws her husband’s attention to how anthropogenic CO2 emissions are certainly helping her cause.

References:

Holbrook, G.P., J. Hansen, K. Wallick, and T.M. Zinnen. 1993. Starch accumulation during hydroponic growth of spinach and basil plants under carbon dioxide enrichment. Environmental and Experimental Botany, 33, 313-321.

Jain, V., M. Pal, A Raj, and S. Khetarpal. 2007. Photosynthesis and nutrient composition of spinach and fenugreek grown under elevated carbon dioxide concentration. Biologia Plantarum, 51, 559-562.

Jin, C.W., S.T. Du, Y.S. Zhang, C. Tang, and X.Y. Lin. 2009. Atmospheric nitric oxide stimulates plant growth and improves the quality of spinach (Spinacia oleracea). Annals of Applied Biology, 155, 113-120.

No-Cream Creamed Spinach

Ingredients
2 pounds baby spinach, washed and cleaned
2 tablespoons olive oil
4 shallots, minced
2 garlic cloves, minced
Salt and freshly ground pepper

Method
1. Blanch half a pound of spinach in salted, boiling water. Immediately, “shock” the blanched spinach in a bowl of iced water. Drain and squeeze out the excess water. Puree in a blender. Set aside.
2. In a large skillet, sweat the shallots and garlic until translucent. Add the rest of the spinach leaves. Toss and sauté until wilted. Fold in the spinach puree. Season with salt and pepper.
Serves 6.




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