In the recent years, our awareness of climate change and the greenhouse effect has increased. By this point, most people know that these are related to carbon emissions, and ever increasing amounts of carbon dioxide in the atmosphere. Among the different practices that have been recommended to reduce the carbon footprint is to plant trees, due to the fact that plants take carbon dioxide and replace it with oxygen during photosynthesis.
It should be worth noting that although the specimens were collected from a river near Hangzhou, the water hyacinth is not native to China. Originally from South America, it is mentioned at the beginning of the study as being "notorious as the world's worst aquatic invasive weed," due to its rapid growth and reproduction rates. Despite this, though, the plant has also been used for several industrial purposes, including the removal of toxins and nutrients from water. The potential to increase the growth of the water hyacinth can be connected to either the increase of invasive species or the opportunity to clean out water systems.
To test the effects of augmented carbon dioxide on this plant, the samples collected from the river were grown at four different nutrient levels--with two different concentrations of carbon dioxide each--to observe their growth and levels of nitrogen and phosphorus. Growth was measured according to the lengths of their roots and shoots, the number of leaves that they had, and the number of clone offspring produced, as well as the rate of the plant's relative growth.
At the end of a seven-week period of measurement, it was found that growth of the samples increased with both the level of carbon dioxide and the amount of nutrients available. What was more, the samples exposed to higher concentrations of carbon dioxide were unaffected if the level of nutrients available decreased, although this was more prevalent for the samples given more nutrients to begin with. It should also be noted that the increase of carbon dioxide had a greater effect on the growth of the roots than on that of the shoots. However, it had little to no effect on the number of leaves or clone offspring.
The amounts of nitrogen and phosphorus in the plants' tissues declined as the levels of carbon dioxide were raised, though these amounts also went down with the amount of nutrients already present. Although the concentrations of both nutrients were lower in the roots with and without the elevated carbon dioxide, the ratio between the levels of phosphorus and nitrogen were smaller in the shoots of the plants.
All in all, the study showed that "plant growth was positively related to culture nutrient level and atmospheric [carbon dioxide] conservation level." The discussion at the end of the research paper also pointed out how these levels compensated for a lack of nutrients, saying,
Our data suggest that though the [carbon dioxide]-induced stimulation on E. crassipes would overbalance the inhabitation caused by nutrient decline between narrow ranges...it would only partly compensate the inhabitation [caused] by nutrient decline between the wide ranges....
Considering the constantly increasing levels of carbon dioxide in our atmosphere today, these results could easily become reality for wherever the water hyacinth is prevalent. For that matter, the study goes on to suggest that this could be applied to other C3 plants. For something as invasive as the water hyacinth, though, the rise in carbon emissions could easily mean that the plants will spread much more rapidly. And since the higher concentrations in carbon dioxide affect the roots of the plants most of all, it will be easier for the roots to incorporate themselves into the native earth.
As was mentioned earlier in the article, the spread of water hyacinth in China can be viewed in a positive or negative light. Although environmental holists concerned with the intrinsic view of the native ecosystem would be appalled that elevated levels of carbon dioxide would cause the invasive species to flourish even more, others might see an advantage in the increase of a plant that could potentially remove toxic waste from water.
Still, the research paper points out that it is too early to make any definitive conclusions about the findings or their implications, saying,
...the [carbon dioxide]-induced increase in net nutrient accumulation would be adventageous with regards to bioremediation efficiency of water eutrophication, but its bioremedial efficiency for refractory organisms and heavy metals under elevated [carbon dioxide] needs further study. Studies on combined impacts of elevated [carbon dioxide] with other environmental factors at larger level are also needed to better manage this two-sided plant in a future climate scenario.
One matter is certain, though: At least there is one organism that seems to be benefitting from the increase of carbon emissions in the atmosphere.
Reference List
Jun-Zhi, L., Ya-Ming, G., Yu-Fei, Z., Guang-Ming, T. (2010). Effects of elevated CO2 on growth of Eichhornia crassipe under four different nutrient levels. Water, Air, & Soil Pollution, 212, 387-394. Retrieved October 13, 2010, from http://www.springerlink.com/content/h714724k0m254278/fulltext.pdf.
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