Hormone

The word hormone is derived from a Greek verb that means to excite. Hormones are found in all multicellular organisms and function to coordinate the parts of the organism. A hormone is a chemical signal. It is produced by one part of the body and is then transported to other parts of the body where it triggers responses in cells and tissues. The concept of chemical messengers and plants first emerged from a series of classic experiments on how plant stands respond to light. Think about this: a houseplant on the windowsill grows toward light. If you rotate the plant, it will soon reorient its growth until its leaves again face the window. The growth of a plant toward light is called photo tropism . in a forest or other natural ecosystem where plants may be crowded.