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Pearltree

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Új lap. Tree. Tree. A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier.

Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development. Flowers and fruit may also be present, but some trees, such as conifers, instead have pollen cones and seed cones; others, such as tree ferns, produce spores instead. Trees play a significant role in reducing erosion and moderating the climate.

Definition Overview Distribution Parts and function Roots. Pearltree (Pearlota pendula) Pearl. Pearl. The most valuable pearls occur spontaneously in the wild, but they are extremely rare. These wild pearls are referred to as natural pearls. Cultured or farmed pearls from pearl oysters and freshwater mussels make up the majority of those that are currently sold. Imitation pearls are also widely sold in inexpensive jewelry, but the quality of their iridescence is usually very poor, and often, artificial pearls are easily distinguished from genuine pearls. Pearls have been harvested and cultivated primarily for use in jewelry, but in the past they were also stitched onto lavish clothing. Whether wild or cultured, gem quality pearls are almost always nacreous and iridescent, as is the interior of the shell that produces them.

Etymology[edit] A pearl being extracted from an akoya pearl oyster. A black pearl and a shell of the black-lipped pearl oyster. Definition[edit] A "natural pearl" or "wild pearl" is one that forms without any human intervention at all, in the wild, and is very rare.