February 15, 2012

Flowers Love CO2

Filed under: Adaptation, Plants

As this time of the years reminds us, flowers never go out of style. Whether it is to celebrate a holiday or make up for some bad behavior, flowers just get it done every time. This has been the case for generations and will be the case from now until eternity. There is a good reason why we have flower shops on every other street corner.

According to AboutFlowers.com, “the U.S. floral industry includes fresh cut flowers, cut cultivated greens, potted flowering plants, foliage plants and bedding/garden plants, making floriculture the third largest U.S. agricultural crop. The U.S. floral industry consists of more than 60,000 small businesses, such as growers, wholesalers, retailers, distributors and importers.” Total revenue for these businesses is over $35 billion annually with 67% of fresh flowers being imported largely from Colombia and Ecuador. Can you name the state leading fresh flower production? California dominates the market with 77% of the US production; Washington produces 6%, Hawaii is at 4%, and Florida, Oregon, and New Jersey each produce 3% of our fresh flowers.

Commercial flower growers are fully aware that higher levels of atmospheric CO2 produce great results in indoor greenhouses, and the industry has dreamed up many creative ways to cheaply produce the magic gas. There is no doubt the CO2 creates better flowers, but maintaining higher levels of CO2 can be expensive and in some cases, not cost effective. Flowers in the real world don’t have to worry about the financial cost of higher levels of atmospheric CO2 – it is coming to them absolutely free given emissions from fossil fuel consumption throughout the world. Flowers today are growing in a world of ever-increasing CO2 levels, and research continues to show us that the flowers are thrilled with the situation.

A recent article on orchids is a case in point. The article appeared in Plant Cell Reports and was written by four scientists from several universities in Japan. While we typically think of orchids as tropical and subtropical flowers for our enjoyment, there are many varieties that grow in temperate and even cold climates. Did you know that vanilla plants are orchids? The underground tubers of some terrestrial orchids can be ground into powder and used in cooking (ground orchid powder shows up in hot beverages and ice cream). Make a trip to Reunion Island and enjoy a rum that is made from the dried leaves of orchids, or if you cannot make the trip, you can purchase any number of perfumes that are derived from the scent of orchids. All of these uses makes us wonder about the future of this highly diverse member of the biosphere.

Norikane et al. grew orchids in glass bottles with atmospheric CO2 concentrations maintained at ambient levels of CO2 (around 380 ppm), 3,000 ppm, and 10,000 ppm to explore what would happen with “super-elevated” levels of CO2; they used cold cathode fluorescent lamps (CCFL’s) to light the plants throughout the experiment. There is a lot of information in the article, but the plantlets absolutely loved the high levels of CO2. When comparing ambient to 10,000 ppm CO2, the young plantlets increased the number of leaves by 29%, they more than tripled the number of roots, they nearly doubled plant height, root length increased by a factor of six, stem diameter increased by 50%, fresh and dry weight of the shoots nearly tripled, and fresh and dry weight of the roots increased by a factor of 20! They transferred the plantlets and after another 30 days, the goodness kept right on going with benefits to every part of the plants (including the chlorophyll content). In their abstract, Norikane et al. note “growth of plantlets, in particular the roots, was remarkably enhanced” (it is very rare to see scientists referring to their results as remarkable). They state at the very end of the article “we will expect that super-elevated CO2 enrichment under CCFL make possible more efficient and higher quality commercial production of clonal orchid plantlets.”

We all know some guys who have gone down the roses road from time to time and left the orchids for the prom crowd. So, in their interests, we searched around and found this oldie-but-goodie article in The New Phytologist from back in 1985 in which roses were grown with elevated concentrations of CO2. The piece was produced by a scientist with the Agricultural University of Norway and the research was funded by the National Agricultural Research Council and the Royal Ministry of Petroleum and Energy of Norway (very interesting).

Mortensen grew roses (Rosa ‘Mercedes’) in growth chambers with atmospheric CO2 maintained at 330 ppm and 1,000 ppm. The plants increased their dry weight by 21% thanks to the extra CO2. Mortensen also grew two varieties of African violets in these chambers, and their dry weights increased by 40.8 and 58.3% given elevated CO2. The violets increased the number of plants producing flowers, the elevated CO2 decreased the number of days to flowering by a full week, and the number of flowers and flowerbuds more than doubled in the chambers with elevated CO2. Maybe you prefer mums instead of orchids, roses, or violets? You guessed it – Mortensen grew two variety of mums as well, and the elevated CO2 caused them to increase their dry weight by 27.8% and 67.1%.

We could go on and on – Mortensen grew lettuce, cucumbers, tomato, moss, ivy, and other flowers, and the CO2 effect on dry weight ranged from 21.4% for the roses to 74.0% for the lettuce. More reasons for happiness, more reasons to give flowers, and more reasons to welcome higher levels of CO2.

References:

Mortensen, L.M. 1985. Nitrogen oxides produced during CO2 enrichment. I. Effects on different greenhouse plants. The New Phytologist, 101, 103-108.

Norikane, A., T. Takamura, M. Morokuma, and M. Tanaka. 2010. In vitro growth and single-leaf photosynthetic response of Cymbidium plantlets to super-elevated CO2 under cold cathode fluorescent lamps. Plant Cell Reports, 29, 273–283.




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