Any of a group of extremely small bacteria that are similar to mycoplasmas in that they have a cell membrane instead of cell walls and can assume a variety of shapes, but are parasitic solely in plants. In many plants, phytoplasmas invade cells of the food-carrying tissue known as phloem and are usually spread by plant-sucking insects, such as the leafhopper, which draws its food from phloem. Phytoplasmas cause some 200 plant diseases affecting several hundred genera of plants. See also mycoplasma.
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