You heard it here first, folks! Today, we invited Peter Pellitier into the studio to elucidate the multi-faceted relationship between plants and carbon dioxide. Peter is a current Ph. D. candidate at SEAS where he researches terrestrial ecology and mycorrhizal fungi. He explained that plants have increased their carbon dioxide uptake by 31% as compared to pre-industrial rates.
Initially, we thought this to be a rather miraculous factoid. To some extent it is; our gracious verdure has begun to acquiesce in our state of rampant emissions and has used carbon dioxide to build its biomass and sequester more carbon — a positive feedback loop! However, carbon dioxide is not the only ingredient in the recipe for photosynthesis. Nitrogen plays an invaluable role and is actually a limiter for the process. As Peter explains, the nitrogen levels in more pristine areas have been gravely affected by the manipulation of nitrogen for the fertilization of agriculture. The effect of the latter on the former is a story told by agricultural runoff and topsoil loss. He points out that “despite the fact that plants are doing a ‘better job’ of getting carbon dioxide out of the atmosphere, they’re still not doing a good enough job to keep pace with the CO2 that humans are releasing.” Hence, as Bella mentioned, global greening is not the end-all-be-all to climate change.
Back to mycorrhizae. This class of fungi commonly forms a symbiotic relationship with plants where both organisms benefit. Within this mutalism (although there exist parasitic mycorrhizae), the fungi latch on to the roots of a plant to increase the depth and surface area covered by the root system. This fragile architecture ultimately increases the uptake of water and nutrients by the plant. In return, the plant allows its prosthetic roots to feed off its supply of freshly baked carbohydrates (made from scratch!), providing energy for the fungus.
As if root extensions weren’t enough, plants are also capable of producing volatile organic compounds (VOCs) as a defense mechanism to guard themselves from predation. Imagine you are a flowering grass. While you’re sequestering carbon and building up biomass, along comes a hungry, hungry caterpillar. Now, although it’s probably too late for you, you send a chemical signal to your surrounding leafy lads. The signal encourages them to up-regulate genes that trigger defenses to ward off that fuzzy, pesky beast (think toxins, unpalatable taste, etc.). A noble goner, you die with integrity and honor.
Now imagine you’re a greenhouse gas — let’s call you Nick Oxide —and you have a friend, Monica Carbon, who is also a greenhouse gas . As the two of you float freely through the sunny, UV-laden atmosphere going about your day and wreaking havoc, you suddenly bump into a molecule named Voc Isoprene, emitted from the plants in the caterpiller story. In the collision, the three of you combine forces and become none other than O. Thry.
Tropospheric ozone (O3, and infamously O. Thry from our visual exercise) is a greenhouse gas that traps heat and contributes to global warming. This is not to say that all, or even the majority of plant-made VOCs magnify the effects of climate change, but it may be something to think about if we’re expecting all this new greenery Peter told us about.
Thanks for stopping by. Be sure to catch us next week.
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