Erica's Original Notes Light is very necessary for plants; therefore, there are few plants growing in the shade of evergreens; most plants found in deciduous woods bloom in the spring before the trees leaf out, also few branches are found within a clump of trees. Vines operate 'on the cheap', using trees and shrubs to get to the light.
In the leaf, sun and CO2, together with chlorophyll and H2O and minerals from the roots, make sugar (glucose) which produces energy. Chlorophyll in advanced plants is in chloroplasts and converts light energy to chemical energy; some chloroplasts move within the leaf cells in response to light, as in duckweed where they lie horizontally in order to receive the maximum light. Sugar is a readily available source of energy, as it is easily dissolved, just like sugar in tea! For this reason, it is stored as starch which is stable. In spring, the sap is sweet and ready for use in the new growth. A compost heap is hot with energy, and the energy produced by one acre of forest in one year would be sufficient power for an average home for 50 years. The annual energy output of plants is staggering.
Lightning: The atmosphere contains 80% nitrogen which is unusable. The intense heat of lightning forces the nitrogen to combine with oxygen, resulting in nitrogen oxides which are water soluble and fall to the earth in rain as dilute nitric acid; this reacts with minerals in the ground to become nitrates.
Sun: The energy of sun, which is caught in water, is stored, whereas that in the air is dissipated.
Rainbow: A rainbow is a band of colours with different wavelengths which appears in the sky when the sun shines after the rain. It is found in the part of the sky opposite the sun. When the rain has been heavy, the rainbow may spread all the way across the sky, with the ends seeming to rest on the earth below. Rainbows are caused by the reflection and refraction of the sun's rays as they fall on drops of rain. Seven colours appear: violet, indigo, blue, green, yellow, orange and red, but they blend into each other so that we are only aware of four or five, and the size of each colour band is dependent on the size of the raindrops, acting like a prism. A complete rainbow shows two bands of colours: the inner, brighter one is the primary bow with red colouring on the outside and violet on the inside of the arch. The outer, or secondary, bow is less distinct, and the colour arrangement is reversed. [Hyperlinks added 2013.]