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Liña 24: == Parénquima vexetal == ~~{{further2\|[[Ground~~== ~~tissue#~~Parenchyma~~]]}}~~ == O parenquima é un tecido fundamental vexetal moi versátil, que realiza as funcións vexetativas da planta. Forma o córtex e a medula dos talos e raíces, o [[mesófilo]] das [[follla]]s, a polpa dos froitos, a nucela dos primordios seminais e o [[endosperma]] das [[semente]]s. As células do parénquima son células vivas e pouco diferenciadas, que permanecen [[meristemo\|meristemáticas]] na madurez, o que significa que poden dividirse se reciben os estímulos xeitados (hormonas vexetais, por exemplo). As súas [[parede celular\|paredes celulares]] [[celulosa\|celulósics]] son finas e flexibles, e xeralmente teñen forma poliédrica cando están formando os tecidos, aínda que adquiren formas máis esféricas se as illamos. Teñen grandes [[vacúolo]]s centrais, que lles permiten almacenar auga, regular os ións e almacenar produtos residuais. The form of parenchyma cells varies with their function. The epidermal parenchyma cells of a leaf are barrel shaped in cross section, but have a variety of outline shapes ranging from simple polygons to strongly branched and interlocked shapes resembling the pieces of a [[jigsaw puzzle]], as in the leaves of ''[[Arabidopsis thaliana]]''. In the epidermis of higher plants, only the guard cells have [[chloroplast]]s. This tissue serves as a barrier wall and protects the internal tissues from injury.<ref name="Leaves" /> In the spongy [[mesophyll]] of a leaf, parenchyma cells range from near-spherical and loosely arranged with large intercellular spaces<ref name="Leaves" /> to branched or stellate, mutually interconnected with their neighbours at the ends of the arms to form a three-dimensional network, as in the red kidney bean ''[[Phaseolus vulgaris]]'' and other [[mesophyte]]s.<ref name="Jeffree etal.">Jeffree CE, Read N, Smith JAC and Dale JE (1987). Water droplets and ice deposits in leaf intercellular spaces: redistribution of water during cryofixation for scanning electron microscopy. Planta 172, 20-37</ref> These cells, with the [[Epidermis (botany)\|epidermal]] [[guard cell]]s of the [[stoma]], form a system of air spaces and chambers that regulate the exchange of gases. They usually contain plastids.<ref name="Leaves" />▼ '''Parenchyma cells''' are thin-walled [[Cell (biology)\|cells]] of the [[ground tissue]] that make up the bulk of most [[Herbaceous\|nonwood]]y structures, yet sometimes their cell walls can be lignified. Parenchyma cells in between the [[epidermis (botany)\|epidermis]] and [[pericycle]] in a [[root]] or [[shoot]] constitute the [[Cortex (botany)\|cortex]], and are used for storage of food. They are mainly present in the soft areas of the stems, leaves, root, flowers, fruits etc. Parenchyma cells within the center of the root or shoot constitute the [[pith]]. Parenchyma cells in the ovary constitutes the '''nucellus''' and are brick-like in formation. Parenchyma cells in the leaf constitute the [[mesophyll]]; they are responsible for photosynthesis and they allow for the interchange of gases.<ref>[http://www.botany.uwc.ac.za/sci_ed/grade10/anatomy/leaves.htm Leaves<!-- Bot generated title -->]</ref> ===Tipos de parénquima vexetal=== Parenchyma is the most common and versatile ground tissue. It forms, for example, the [[cortex (botany)\|cortex]] and [[pith]] of stems, the cortex of roots, the [[mesophyll]] of leaves, the pulp of fruits, and the [[endosperm]] of seeds. Parenchyma cells are living cells and may remain [[meristematic]] at maturity, meaning that they are capable of [[cell division]]. They have thin but flexible [[cellulose]] [[cell wall]]s, and are generally polygonal when close-packed, but approximately spherical when isolated from their neighbours. They have large [[central vacuole]]s, which allows the cells to store and regulate ions, waste products and water. As células do parénquima teñen moitas posibles funcións, polo que se distinguen varios tipos de parénquima vexetal: * In [[leaf\|leaves]], they form the [[mesophyll]] and are responsible for [[photosynthesis]] and the exchange of gases,<ref name="Leaves">[http://www.botany.uwc.ac.za/sci_ed/grade10/anatomy/leaves.htm Leaves<!-- Bot generated title -->]</ref>, parenchyma cells in the [[mesophyll]] of leaves are a specialized parenchymatous tissue known as [[chlorenchyma]] (parenchyma with chloroplasts).▼ ~~Parenchyma cells have a variety of functions:~~ * Storage of starch, protein, fats and oils and water in roots, tubers (e.g. [[potato]]), seed [[endosperm]] (e.g. [[cereal]]s) and [[cotyledon]]s (e.g. [[pulses]] and [[peanut\|groundnut]]) ▼ ▲In [[leaf\|leaves]], they form the [[mesophyll]] and are responsible for [[photosynthesis]] and the exchange of gases,<ref name="Leaves">[http://www.botany.uwc.ac.za/sci_ed/grade10/anatomy/leaves.htm Leaves<!-- Bot generated title -->]</ref> parenchyma cells in the [[mesophyll]] of leaves are a specialized parenchymatous tissue known as [[chlorenchyma]] (parenchyma with chloroplasts). [[Secretion]] (e.g. [[hydathode]]s, [[nectary\|nectaries]] and cells lining the inside of resin ducts)▼ ▲Storage of starch, protein, fats and oils and water in roots, tubers (e.g. [[potato]]), seed [[endosperm]] (e.g. [[cereal]]s) and [[cotyledon]]s (e.g. [[pulses]] and [[peanut\|groundnut]]) Wound repair and the potential for renewed meristematic activity▼ ▲[[Secretion]] (e.g. [[hydathode]]s, [[nectary\|nectaries]] and cells lining the inside of resin ducts) Other specialized functions such as aeration ([[aerenchyma]]) and support▼ ▲Wound repair and the potential for renewed meristematic activity ▲Other specialized functions such as aeration ([[aerenchyma]]) and support ▲The form of parenchyma cells varies with their function. The epidermal parenchyma cells of a leaf are barrel shaped in cross section, but have a variety of outline shapes ranging from simple polygons to strongly branched and interlocked shapes resembling the pieces of a [[jigsaw puzzle]], as in the leaves of ''[[Arabidopsis thaliana]]''. In the epidermis of higher plants, only the guard cells have [[chloroplast]]s. This tissue serves as a barrier wall and protects the internal tissues from injury.<ref name="Leaves" /> In the spongy [[mesophyll]] of a leaf, parenchyma cells range from near-spherical and loosely arranged with large intercellular spaces<ref name="Leaves" /> to branched or stellate, mutually interconnected with their neighbours at the ends of the arms to form a three-dimensional network, as in the red kidney bean ''[[Phaseolus vulgaris]]'' and other [[mesophyte]]s.<ref name="Jeffree etal.">Jeffree CE, Read N, Smith JAC and Dale JE (1987). Water droplets and ice deposits in leaf intercellular spaces: redistribution of water during cryofixation for scanning electron microscopy. Planta 172, 20-37</ref> These cells, with the [[Epidermis (botany)\|epidermal]] [[guard cell]]s of the [[stoma]], form a system of air spaces and chambers that regulate the exchange of gases. They usually contain plastids.<ref name="Leaves" /> == Notas==

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