One of the goals of photosynthesis research is to improve plants’ productivity to a level adequate for human food and energy needs. As of now, plants are currently doing a good enough job to reproduce themselves and mostly sustain our biosphere, but we would still like to kick this up a notch. Scientists are using a variety of tools to tackle this problem. The most notable is using genetics- either by breeding new varieties or genetically engineering new traits by manipulating specific genes sometimes between different organisms. Today’s post features another type of engineering to improve plants ability to photosynthesize- nanotechnology.
Researchers at MIT report that plant chloroplasts can be infused with carbon nanotubes to impart increased photosynthetic capacity (as much as 49% greater than unaltered chloroplasts and 30% in whole plants). Much like the X-Men character Wolverine was infused with the metal alloy adamantium to render his skeleton indestructible and give him those awesome retractable claws, plant chloroplasts can be infused with special materials to give them what amounts to photosynthetic superpowers. No, they didn’t use adamantium. The material used in their study was carbon nanotubes fused to cerium oxide nanoparticles aka nanoceria.*
You may be wondering to yourself, “What exactly are photosynthetic superpowers?”**
The nanoceria are able to absorb infrared light, which no native plant pigments can do. Plant pigments like chlorophylls and carotenoids do a good job of covering the visible light spectrum, but this is only half of the incident solar energy beaming down on them all day. The researchers in this study conclude that the boost in photosynthetic capacity is in part due to the fact that the nanotubes absorb light energy beyond the visible range and can then transfer this energy to the photosynthetic machinery. In this way, the nanotubes are acting like an antenna- a giant antenna that doesn’t just boost the signals you’re already getting, but allows access to a whole set of new premium channels.
The nanotubes have a couple of other advantageous side effects as well. The cerium oxide nanoparticles are quite effective radical oxygen species (ROS) scavengers. Remember when I told you photosynthetic organisms have a complicated relationship with light? They need enough of it to live, but too much can be extremely damaging. This is why blasting plants with bright light at all times isn’t necessarily the best way of improving their growth and productivity. Likewise, improving their ability to capture light can also be dangerous. This is all due to the fact that overloading the photosynthetic circuitry with too many electrons can start to generate ROS which in turn irreversibly damage proteins, pigments and DNA they encounter. Since the nanoceria are quite good at scavenging or capturing and inactivating ROS, they also boost photosynthesis by helping out plants’ innate systems for dealing with this problem. Again, like Wolverine, plants have some level of ‘healing powers’ when it comes to dealing with light, but the nanotubes help kick it up a notch. Wolverine’s adamantium doesn’t really help with his healing powers, but coating his skeleton with it means it doesn’t get broken as easily and he doesn’t have to use his healing powers to mend broken bones. In the same way, the nanoceria prevent some damage before it happens so the plants don’t have to waste their resources on repairing damage caused by ROS.
In true superhero style, the nanotube-infused chloroplasts’ powers don’t stop there. They also confer the ability to detect certain chemicals in the environment. Yes, just like Wolverine has heightened senses (if he twitches is nose, he’s knows you’re there!), chloroplasts containing nanotubes do too. Different types of nanoparticles have been developed to detect toxins and pollutants like nitric oxide, sarin gas, and TNT. Integrating this technology into a photosynthetic organism may allow plants to become stealthy biodetectors of these chemicals. No longer would they be merely scenery, but solar-powered secret agents (green-ops?) with skills no training could ever provide.***
These super powers may not be indestructible retractable claws, but it’s a good start down the path to lots of useful applications.
Conclusion: Plants infused with nanoceria definitely qualify as super photosynthesizers, but we still have some work to do to put this into useful practice beyond the lab.
How do nanoparticles and enhanced photosynthesis affect plants over their entire lifespan vs. short experiments in the lab? Does this kind of boost in the light reactions translate into an increase in biomass? Sure, the light reactions could always use some help when sunlight is less than its brightest, but the real rate-limiting pathway is the dark reactions. (I’m looking at you Rubisco!).
How can this technology be translated into field agriculture to boost productivity of crops? Is it worth it? It’s not like you can propagate the nanotubes biologically, but who knows, maybe in the future tractors will be outfitted with attachments to infuse or spray seedlings with nanoparticles. In terms of calculating potential for improving plant productivity, photosynthetic energy conversion remains a variable in the equation that has yet to be thoroughly tapped when it comes to improving crop plants. Using carbon nanotubes to extend the spectrum of useful light into the infrared would definitely help plants breakthrough some yield ceilings we are seeing.
How can we turn our scenery into useful biosensors for pollutants? What kinds of chemicals can they detect and how can that be cheaply and easily measured? Sure, everyone and their grandma has a satellite and a drone these days, but are we really going to have to laser scan our environment every hour? How about a nice color change or wi-fi signal that NORAD can detect?
Speaking of wi-fi, why can’t we engineer plants with nanotechnology that allows them to have other superpowers, like transmitting wi-fi signals? Solar-powered free internet anywhere! Finally, getting plants to release something useful besides oxygen****, and it would go a long way to keep me from going over my monthly data plan limits.
These are all questions and exciting possibilities that will keep photosynthesis researchers like the Strano lab busy for years to come.
*IMHO, ‘nanoceria’ is itself a name worthy of comic book lore. Maybe DC Comics can do a series where Swamp Thing is infused with nanoceria boosting his plant-like powers.
** You must be new here. Welcome.
***K-9 units may be relegated to history. SWAT, move over for SWNTs. (You’ll get it if you read the paper).
****It’s important to me that you catch the sarcasm in that phrase. If you’ve been breathing today, thank a photosynthetic organism.
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