Class Project to Blog Post: A Word on Photosynthesis

Greetings! Once more, it is the second Saturday of the month, and I find myself scrambling to put together a post about science. Fortunately, I’m a genetics student two weeks into her third semester, and need not look too far for interesting topics.

Inspiration comes in various forms. Why shouldn’t it come in the forms of happy little houseplants?

Image result for crassula ovata
A jade plant, Crassula ovata.

I’ve kept jade plants for years. They’re a kind of succulent (a water-conserving plant with fleshy stems and leaves, something between a normal plant and a cactus) which, not surprisingly, grows well even when you forget to water it. Plus, every time a branch breaks off, if you stick it in a pot, you get a new plant. (I keep getting more of them that way.) They look cool, make great bonsai projects, and even flower once in a blue moon. And as this is a science post, not a gardening post, I bet you’ve already guessed that jade plants are also scientifically interesting.

All plants use photosynthesis to “fix” carbon dioxide into glucose, which can then be broken down in respiration to get energy. It’s more or less equivalent to making one’s own food. There are different ways of doing this; the most common is C3 photosynthesis, more or less the “normal” pathway. C4 photosynthesis is found most often in tropical plants, and involves some extras added to the C3 pathway to maximize carbon dioxide uptake in environments where the gas’s availability is limited. In both of these pathways, stomata (small openings in plants’ leaves) allow carbon dioxide into the plant.

Crassulacean acid metabolism, or CAM, photosynthesis adds on further to C4. It is found mostly in desert succulents like cacti and jade plants, and in fact was named after the jade plant’s family, Crassulaceae. In CAM photosynthesis, the stomata open only at night, when the temperature is lower and the water within the plant will evaporate less than it would during the day. The plant then takes in carbon dioxide, fixes it to an intermediate molecule, malate, and stores it to be processed during the day. This cool adaptation helps cacti and succulents survive in their desert environment.

One more note: I haven’t said anything about the first part of the title yet. Well, I’m taking genetics this semester, and I need to do an honors project on a gene that interests me. While poking around for genes involved in drought resistance in plants, I rediscovered CAM photosynthesis, which I learned about a few years ago and thought was really cool. There you are; inspiration from a class project. It really does come from various places.

(My source for this post was The Physiology of Flowering Plants: Their Growth and Development, third edition, by H.E. Street and Helgi Opik.)

Isn’t CAM photosynthesis cool? (If you don’t think so, I totally understand. I know lots of people probably don’t get why I’m a plant nerd.) Have you ever had a jade plant, or a cactus or something similar? If so, what was your experience with it? Tell me in the comments!