In an amazing example of a closed but functional ecosystem, David Latimer has grown a garden sealed inside of a giant glass bottle that he has only opened once since he started it almost 57 years ago.
Latimer planted the garden on Easter Sunday in 1960. He placed some compost and a quarter pint of water into a 10-gallon glass carboy and inserted a spiderwort sprout using wires. In 1972, he opened the garden again to add a bit of water. With that one exception, the garden has remained totally sealed – all it needs is plenty of sunlight!
It might seem strange to some that a totally sealed garden would thrive like this, but it’s not – the garden is a perfectly self-sufficient ecosystem. The bacteria in the compost break down the dead plants and break down the oxygen given off by the plants, turning it into the carbon dioxide that the plants need to survive. The bottle is an excellent micro version of the earth as a whole.
Bottle gardens work because their sealed space creates an entirely self-sufficient ecosystem in which plants can survive by using photosynthesis to recycle nutrients.
The only external input needed to keep the plant going is light, since this provides it with the energy it needs to create its own food and continue to grow.
Light shining on the leaves of the plant is absorbed by proteins containing chlorophylls (a green pigment).
Some of that light energy is stored in the form of adenosine triphosphate (ATP), a molecule that stores energy. The rest is used to remove electrons from the water being absorbed from the soil through the plant’s roots.
These electrons then become ‘free’ – and are used in chemical reactions that convert carbon dioxide into carbohydrates, releasing oxygen.
This photosynthesis process is the opposite of the cellular respiration that occurs in other organisms, including humans, where carbohydrates containing energy react with oxygen to produce carbon dioxide, water, and release chemical energy.
But the eco-system also uses cellular respiration to break down decaying material shed by the plant. In this part of the process, bacteria inside the soil of the bottle garden absorbs the plant’s waste oxygen and releasing carbon dioxide which the growing plant can reuse.
And, of course, at night, when there is no sunlight to drive photosynthesis, the plant will also use cellular respiration to keep itself alive by breaking down the stored nutrients.
Because the bottle garden is a closed environment, that means its water cycle is also a self-contained process.
The water in the bottle gets taken up by plants’ roots, is released into the air during transpiration, condenses down into the potting mixture, where the cycle begins again.