Answer:
The Total Mechanical Energy
As already mentioned, the mechanical energy of an object can be the result of its motion (i.e., kinetic energy) and/or the result of its stored energy of position (i.e., potential energy). The total amount of mechanical energy is merely the sum of the potential energy and the kinetic energy.
Explanation:
The Luminosity of a star is proportional to its Effective Temperature to the 4th power and its Radius squared.
Technically speaking, there are many "levels" of a plant for which this may hold true. I think the one you are referring to is the chloroplast. It takes in the light energy from the sun, water and carbon dioxide, and performs photosynthesis on them to produce sugar and oxygen. A leaf would also fit the description as this is a very general question.
Wood, water, Forests. The rest can have harm to the nature.