wtorek, 17 października 2017
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Botanika (96)

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! EN_90273520_0002 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Pollen grains, computer artwork. Pollen grains are reproductive structures produced by flowers. They display a great variation in their size, shape and surface texture. The outer wall (exine) is often highly sculpted to aid in their dispersal on the wind and by pollinators such as insects. Flowers may collectively produce many hundreds of millions of pollen grains in a flowering season. The pollen grain surfaces are used by botanists to categorize and recognize plants. Each pollen grain contains a male gamete (reproductive cell) that is intended to fertilise an egg or ovule (female gamete), and initiate the formation of a seed for a new plant.
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! EN_90250821_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Cellulose production. Artwork of a sectioned plant cell wall, showing the production of strands of cellulose (brown, upper frame). These form much of the cell wall, providing the cell with a rigid and strengthened structure. The cellulose is produced by rosettes (three seen) in the plasma membrane of the cell (horizontal yellow layer). The action of the rosettes is directed by cortical microtubules (grey tubes) underneath the membrane. Cellulose production is mediated by the enzyme cellulose synthetase in the rosettes. 36 cellulose strands are produced by each rosette, and these aggregate to form microfibrils, which are shown cross-linked by
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! EN_90251383_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Chloroplast. Artwork of a chloroplast in close-up, in a sectioned plant cell. Chloroplasts are one of the features that distinguish a plant cell from an animal cell. They contain chlorophyll, a green pigment that is needed to use energy from sunlight during photosynthesis, when carbohydrates are made from carbon dioxide and water. It contains stacks (circular) of flattened membranes, called grana, that contain the chlorophyll. It is thought that, during cell evolution, chloroplasts originated as once-independent micro-organisms. The cell wall (yellow), the nucleus (pink), and two peroxisomes (blue spheres) are also seen. Peroxisomes contain enzymes that help oxidise harmful materials.
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! EN_90273111_0002 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY NOT FOR USE IN EDUCATIONAL POSTERS Plant cell structure. Artwork of a sectioned plant cell. The features that distinguish a plant cell from an animal cell are the cell wall (yellow) and the chloroplasts (green ovals circling the cell). The large central vacuole (liquid and gas-filled space) also contrasts with the many small vacuoles of an animal cell. Chloroplasts contain a pigment, chlorophyll, which is used in photosynthesis. The nucleus (pink, centre left) has been cut open to show the nucleolus (sphere), and is found in plant and animal cells, as are the energy-producing mitochondria (orange ovals) and peroxisomes (blue spheres that contain enzymes to break down harmful materials). See G450/078 for an animal cell.
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! EN_90273115_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Plant cell membranes. Cutaway artwork of the membrane channels that connect all the cells in a plant. They are called plasmodesmata and are seen running vertically through the cell wall, which is sectioned in an L-shape. Chloroplasts (green) are seen in the lower cell, and folds of membranes are seen in the upper cell. The piece of membrane that runs along a plasmodesma is named a desmotubule. It is an extension of the folded membrane that is called the endoplasmic reticulum (ER) and creates a single membrane system throughout a plant. This also allows plant viruses to spread. The chains of small yellow spheres on the ER are ribosomes where proteins are synthesised.
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! EN_90273483_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Pollination. Computer artwork of pollen grains (yellow spiky balls) on the pistil (red) of a flower. Pollen grains contain the male sex cells (gametes) of a flowering plant. The pistil is the flower's female reproductive parts. Once the pollen has landed on the pistil, the male gametes travel to the ovaries (not seen), where they fertilise the female gametes (ovules) to form the seeds that may grow into new plants.
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! EN_90282693_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Tree water transport. Artwork illustrating the movement of water through a tree (blue arrows). Water is taken up by the root hairs (bottom left) on the roots. It moves upwards through the tree, through the xylem tissue, the rigid woody tissue seen in the circle at lower left. Water is lost from the leaves by transpiration. This is the evaporation of water out of pores (stomata, top right) in the leaves. Trees can reduce their transpiration rate in dry air by closing their stomata. Mineral ions are transported in the water column, also called the transpiration stream.
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! EN_90246539_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Opium poppy. Illustration of a flowering opium poppy, Papaver somniferum. The flower (red) contains a yellow starfish-like stigma. When the petals fall the stigma and carpel (capsule), are left (as at upper centre). The carpel contains young seeds. It is from the sap of these unripe capsules that crude opium is harvested. Crude opium contains numerous alkaloids including morphine, heroin & codeine. It is used medicinally as a sedative and to relieve pain. However, opium is extensively used as a narcotic drug, forming dependency at an early stage.
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! EN_90246533_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY St John's wort. Illustration of the flowers and leaves of a St John's wort plant (Hypericum perforatum), which is used in herbal medicine. St John's wort grows wild throughout Europe in dry and sunny positions. The leaf tips and flowers are used to treat a variety of ailments, but are most commonly used as an anti-depressant. Tablets made up of concentrated parts of the plant can be bought for this purpose. In traditional herbal medicine, the preparations were used for treating intestinal parasites, lung disorders, bladder problems and diarrhoea. In ancient times, the plant was used to ward off evil spirits.
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! EN_90246679_0003 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Cannabis. Computer artwork of the leaf of the hemp or marijuana plant, Cannabis sativa. This plant is used as an intoxicating drug. Native to central Asia it is cultivated for three products: fibre from the stems, seed oil, and the drug. The active ingredient of the drug is a resin from glandular hairs on the leaves, stems and flowers. The plant is a fast-growing annual and a common weed in northern India. In good conditions it can grow to over five metres tall. Male and female flowers are borne on different plants, the females being the most potent as the drug is most concentrated in them.
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! EN_90246571_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Mineral deficiencies in leaves. Illustration of the leaves of a plant, showing the effect of excessive use of fertiliser versus various mineral deficiencies. The growing seedling (at centre right) should have sufficient room in its pot to grow and absorb fertiliser nutrients. At top, a surplus of fertiliser will cause green leaves to curl under. At centre left, nitrogen deficient leaves become pale in colour. Phosphorus deficiency is manifested in curled leaves with purplish undersides (lower left). While a leaf suffering a lack of potassium develops bronze edges (at bottom right).
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! EN_90246639_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Shepherd's Purse. Illustration of the Shepherd's Purse plant, Capsella bursa-pastoris. The plant is seen with flowering parts (at right) and without. The pubescent basal leaves form a rosette with a tap-root; erect stems bear white-petalled flowers at their tips; the fruits are triangular (as seen beneath the flowers) containing oval seeds. The whole plant can be used for medicinal properties, including the treatment of uterine haemorrhage, nose bleeds, urinary calculosis, and was at one time a drug for malaria. Shepherd's Purse grows profusely as a garden weed and on waste ground, widespread throughout Europe.
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! EN_90246540_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Dicotyledon leaf. Illustration showing the anatomy and cell structure of a dicotyledon leaf. The lower surface of the leaf is seen at top. Stomata (brown, pores) are present on the lower epidermis through which gaseous exchange occurs. Under the one- cell thick epidermis, two layers of mesophyll cells are found. Spongy mesophyll (green) consists of loosely packed cells; a palisade layer (yellow) contains cells important in photosynthesis. At centre left, a leaf vein (vascular bundle) is surrounded by a bundle sheath (orange); within the sheath are xylem (pink) and phloem (white) cells which transport water and nutrients.
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! EN_90263828_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Flower anatomy. Illustration of parts of a flower, seen in longitudinal section. The flower is borne on a stalk, with the floral parts attached to a thickened receptacle. Sepals (green) are leaf-like structures that enclose and protect the flower when it is still a bud. Larger petals (red) are usually brightly coloured and may serve to attract pollinators. Within the petals are the male stamens, each made up of a filament and an anther bearing pollen. At centre is the female ovary (here cut through) bearing one or more ovules which may become seeds. The ovary has a long style with a stigma at its tip.
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! EN_90246566_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Illustration of the vascular system in a plant root. Cross-sections through different layers of this root show elements of its internal anatomy. At lower frame, surface root hairs are involved in water absorption from the soil; the single outer layer of cells (exodermis) and thicker cortex are seen. At centre, the root's internal vascular system contains different types of cells: four groups of phloem cells (two groups are visible here, dark brown); a central area of angular xylem cells with thick lignified walls. Xylem vessels transport water and mineral salts from the root upwards; phloem conducts food down to the root.
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! EN_90254260_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Cutaway illustration of a plant chloroplast, the unit within the leaf which manufactures the plant's food supply - starch - during photosynthesis. Contained within a double unit membrane are sheet- like lamellae (also called thylakoids) that support the the granal stacks, represented here as stacks of coins. The grana contain the photosynthetic pigments (chlorophylls) which are active in the conversion of the sun's energy into chemical energy. The chloroplast's internal structure is adapted to maximise the amount of light reaching the chlorophyll pigments.
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