In the process some of the mass of the hydrogen atoms is converted into energy in the form of light. The same process occurs in thermonuclear (fusion) bombs. In the Sun the process occurs in a controled manner. In a bomb it happens all at once in a big chain-reaction explosion.
Phloem. Definition. noun. A tissue in a vascular plant that functions primarily in transporting organic food materials (e.g. sucrose) from the photosynthetic organ (leaf) to all the parts of the plant.
Phloem tissue is surrounded by strong cells called fibers, which are a type of sclerenchyma, and parenchyma cells that form the cortex. Outside the phloem ring is the bark, a ring of boxy, waterproof cells that help protect the stem.