Say we start with an apple seed. It contains a germ and an energy source. The stored energy must be of sufficient quantity to enable the germ to differentiate into roots, stem, and leaves. At some point, presumably early in development, the seedling becomes self-sufficient in energy production. In order to grow, however, it must produce more energy than it expends. And so much more so to produce fruit.
Moreover, the environment changes seasonally and there are good years and bad years. Over it’s lifetime, to be viable, a tree must, on average, produce more energy than it expends.
Given how fond humans are of eating and breathing plant products, I figure there’s lots known about this. But I’m double-durned if I can find much.
I’m interested in the energy economy of plants in general so resources would be appreciated. When I’m hiking in the Pac NW, I wonder about some specifics, too. For instance, what’s the average annual energy surplus of a 70 ft tall Douglas Fir? Or what about a similarly sized cedar?
Sorry if the answers are a simple google search away and I missed them but honest, I tried.
Here is where you begin to go off-track. The plant does not produce more energy than it expends; it converts sunlight into chemical energy, and the amount of chemical energy converted is exactly as much as it expends. No more, no less. The plant will divert some of that energy into growth, some into reproduction (fruit and seeds) and some into storage (usually in its roots). To be successful, it must not spend more on reproduction (for example) than needed for adequate growth, or store more than needed to withstand times of drought.
Plants don’t produce energy. They consume energy. That energy generally comes in the form of sunlight. There’s no surplus of energy. All of the energy that they absorb gets used up in photosynthesis.
The basic “energy equation” of plants is this:
water + carbon dioxide + light energy = sugar + water + oxygen
You’ll note that there is water on both sides of that equation. This references the fact that the water is used as an electron donor in oxygen production. The amounts of water on either side of the equation aren’t equal.
The energy in the seed comes from stored sugars, which were ultimate created by sunlight energy.
Plants generally absorb maybe 3 to 5 percent of the incoming sunlight and use it in photosynthesis. The rest of the energy gets “wasted” into heat.
The amount of sunlight striking the Earth varies for different parts of the world, but you can generally assume it to be somewhere in the neighborhood of 100 to 150 watts per square meter.
That’s an excellent question. I don’t have an excellent answer. But the percentage stored away would vary wildly among types of plants, as they have different storage strategies. I think in particular of a certain vine that produces a ginormous tuber over time verses other plants that store just enough energy to “reboot” themselves the next year (like common bulb plants such as tulips.)
I found acouple of studies that might interest you.
(ETA: seeing the other answers that were posted as I was working on mine, I think the OP is really talking about the ratio of energy used for growth to energy stored away.)
DIdn’t mean to imply I thought plants produced energy in the sense you mean. I understand they store light energy as chemical energy. When I wrote, “produce energy,” I meant, “produce chemical energy from solar energy.”
Next time you’re hiking in the PNW, stop and build a campfire. Ponder how much heat you’d get if you burned an entire tree. Divide that by the age of the tree. There’s your energy storage rate.
After you’ve found out the total energy content in the entire forest … you’ll get a bill telling you the dollar amount of the wood … be-jesus you be careful when you build your campfire …
You’ve had some help so far. And I hate to be beating an already whipped horse, but this statement, right here, is incorrect. And I just wanted to point that out before you make more of them, in your next dozen posts.
There’s enough stored chemical energy to grow a tiny tap root, split a seed coat, and unfold a tiny stem. Without sunlight, you won’t get leaves, the shoot will simply die. You can test that any time you want with a single seed kept in a fold of moist paper towel in the dark vs one left in moist paper towel in the light.