Part 2: Plant Structure


Although leaves are multipurpose organs, which can be found in a variety of shapes, they seem to be specially engineered for photosynthesis. They are the major site for sunlight absorption (the energy source that powers photosynthetic reactions) through chloroplasts (specialised organelles where photosynthesis actually occurs). Chloroplasts contain chlorophyll, a blue-green photosynthetic pigment that absorbs light from the blue-violet and red ranges of the visible light spectrum, reflecting only green, the colour of leaves and other plant parts. The shape of leaves is also important to photosynthesis. All leaves are positioned on the stem of each specific plant to provide maximum amount of surface area available for exposure to sunlight. Plants typically produce a large number of leaves because sunlight comes from every direction of the sky throughout the day. Having as many leaves as possible allows constant exposure of photosynthetic cells to sunlight, and in turn, the constant production of food through photosynthesis. In addition to providing a site for photosynthesis, leaves provide storage, support, and protection to the plant.
Some of the more common essential oils are isolated by distillation from the leaves of herbaceous plants such as basil, oregano, peppermint, rosemary, and shrubs and trees such as tea tree, eucalyptus  etc. Cypress and white fir essential oils are distilled from the needles of their trees.

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