Nutrition
St. John's wort is autotrophic which means it creates it's own food. It accomplishes this through photosynthesis. The root system is also important in the way it receives it's water and nutrients.
Photosynthesis is a process where plants use energy from sunlight
to produce sugar. Plants have chloroplasts containing chlorophyll
that absorb light from the sun. The light energy is converted to
chemical energy to produce organic compounds. Photosynthesis uses
both light reactions and dark reactions. Light reactions convert
light to energy in the form of ATP. Dark reactions use energy and
carbon dioxide to create glucose through the Calvin cycle. Plants
absorb water through their roots and then use the hydrogen and
oxygen. The equation for photosynthesis is:
6CO2 + 6H2O + sunlight --- sugar + 6O2 + H2O
Since most nutrients are formed at the top of the plant and most water is absorbed at the bottom, you may wonder how the rest of the plant obtains anything. The answer is the plants circulatory system made of xylem and phloem. Xylem is responsible for transporting water up the stem to the leaves. This water is then available for photosynthesis. Phloem transports glucose, produced in the cells by photosynthesis, to the roots.
The roots are essential to the entire process. They are semi-permeable and are able to absorb water through osmosis. This is why it is critical to have the horizontal spreading root system. Since the roots do not go deep into the ground they must spread out to create as much surface area for absorption as possible. Without the correct amount of water, photosynthesis will not be possible.