The adjective is also used - perennial which can lead to some confusion - to refer to the foliage of a perennial plant if it is not renewed each year at a time, but remains green in all seasons. We say that the plant is "evergreen" or that the plant is evergreen . When a leaf is said to be perennial is also to indicate that lasts more than two years, the plant is evergreen.
This term is generally applied to plant grass or shrubs rather than small shrubs or trees great, but used too rigorously applied to the larger species and longer lasting flowers and produces seeds more than once in her life.
Herbaceous perennials are those that are not permanent woody tissue. In warm climates can grow continuously. In seasonal climates, their pattern of development suited to the growing season. In cooler climates generally grow and bloom during the warm season of the year and the foliage dies every winter . New growth occurs from the tissue or rhizome existing rather than their seed , like annuals and biennials. In some cases, these perennials may retain their foliage all year round, even in seasonal climates.
Perennial plants dominate most natural ecosystems. The perennial wild grasses and perennials, are usually better competitors than annuals, especially in poor growing conditions. This is because they have a larger root system that can access to water and nutrients from the ground more easily.
Evergreen plants typically found in California, Chile, South-Africa and South America.
The plastids , plastids or plastids are organelles eukaryotic cell, typical of plants and algae. Its main function is the production and storage of important chemical compounds used by the cell . Usually contain pigments used in photosynthesis , although the type of pigment present may vary, determining the color of the cell.
The primary plastids are unique evolutionary branch that includes the red algae , the green algae and plants . There are secondary plastids have been acquired by endosymbiosis from other evolutionary lineages, which are modified forms of eukaryotic cells plastidiadas.
Plastids of plant organelles present as relatively large ellipsoidal in shape, and generally numerous. In one square millimeter of a blade section, there may be more than 500,000 chloroplasts . In protists are often unique structures that extend more or less widely throughout the cytoplasm. Are limited in the rest of the cytoplasm by two structurally different membranes. Often they are colored by pigments soluble nature. Like mitochondria, they have circular DNA, and naked. Plastids of several eukaryotic groups are remarkably diverse. Those in plants provide a convenient reference.
Are delimited by the plastid envelope formed by two membranes, outer membrane and the membrane plastid inner plastid. The space between them, called intraplastidial space, has a distinct composition and is homologous to the periplasmic space in bacteria.
Chloroplast inner space, the stroma , vesicles containing crushed calls thylakoid whose inner lumen or cavity is continued sometimes periplastidial space, especially in chloroplasts juveniles ( proplastids ). Thylakoids, extending more or less parallel, locally form stacks called grana (granum Latin neuter plural). Of the thylakoid membranes form part of photosystems , complexes of proteins and pigments responsible for the light phase of photosynthesis .
The processes of the dark phase of photosynthesis, carbon fixation ( Calvin cycle ) occur in solution in the stroma, as determined using the energy in the thylakoid ATP during the light.
Resides in the stroma plastid DNA , a smaller version of the bacterial chromosome from which the bearer of a limited set of genes. As is common in bacteria, green plastid DNA presents in the form of a single circular chromosome. The plastid chromosome genetic information directs the formation of a limited number of proteins, the rest are imported from the cytoplasm. For the plastid protein synthesis has its own ribosomes that are logically the type prokaryotic (bacterial). Plastids multiply by bipartition, once doubled the plastid DNA.
In plant cells chloroplasts move and orient each time the most appropriate for capturing light.
Chloroplasts (usually in the plant cells and algae). Perform photosynthesis . Chloroplasts are organelles in eukaryotic photosynthetic organisms involved in photosynthesis. They are limited by an envelope formed by two concentric membranes and contain vesicles, the thylakoids, which are organized pigments and other molecules that convert light energy into chemical energy.
Chromoplasts (only in cells of plants and algae). Synthesize and store pigments. Its presence in plants determines the color red, orange or yellow of some fruits, vegetables and flowers. The color of the chromoplasts is due to the presence of certain pigments, such as carotene, red and xanthophylls, yellow. For example, tomatoes and carrots contain many carotenoid pigments.
Leucoplasts : these plastids are colorless and are found in plant cells in organs not exposed to light, such as roots, tubers, seeds and organs that store starch.
Plastids multiply by bipartition. Protoplasts grow along with the meristematic cells. In its development, through invaginations of the inner membrane, plastids acquired a large area. In this inner surface, photosynthetic pigments are located in an orderly manner. In the darkness of plant protoplasts can be transformed into crystalline Estruturas called etioplasts, which by the effect of light, can in turn become photosynthetically active plastids. Plastids that are damaged or are senile often present within lipid droplets, known by the name of plastoglobuli.
In sexually reproducing organisms, the plastids are transmitted through the gametes, in many cases through the female gamete. Plastid DNA is specific and is called DNA plastid, and differs from the DNA nuclear by the relationship between the bases and thickness. plastid DNA is a circular double strand is replicated by a DNA polymerase-specific plastid. and there is also a plastid RNA polymerase-specific transcription. Part of the plastid proteins are synthesized from the plastid DNA of 40 nm in length, and some nuclear DNA. Plastid genes form the plastome, while the set of plastids of a cell is called plastidoma. The ribosomes of plastids are smaller than the cytoplasm , with a sedimentation rate of 70 s. These ribosomes plastidiales are similar to those of prokaryotes. In photosynthetic bacteria and cyanobacteria in photosynthetic pigments are not placed in special organelles, but cromatoplastoplastos, whose structure is similar to the thylakoids of the plastids of eukaryotic cells.
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