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Published byBrianna Walters Modified over 8 years ago
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Either woody or nonwoody Generally, adapted to support leaves; also transport materials and provide storage -stolons – grow along soil surface and produce new plants (strawberry) -tubers – enlarged, short, underground stems used for storing starch (potato) -succulent – fleshy, water-storing stems (cactus)
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Stems grow in length at tips (apical meristem) and in diameter (lateral meristem) Each leaf is attached to the stem at a node. The spaces between nodes are internodes. Bud – apical meristem capable of developing into a new shoot system, enclosed by specialized leaves (bud scales) - lateral – located at nodes - terminal – located at tips of stems
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Dermal tissue – represented by epidermis (protect plant and reduce water loss while allowing gas exchange) Ground tissue – pith and cortex in dicots and gymnosperms, cortex only in monocots Vascular tissue – each bundle contains xylem (towards inside) and phloem (towards outside) -monocots – scattered throughout stems (monkey faces) -dicots and gymnosperms – single ring, with secondary tissues replacing primary tissues
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Stems increase in width (thickness) due to division of cells in the vascular cambium (lateral meristem) More secondary xylem is produced than secondary phloem -heartwood – darker wood in the center that no longer transport water -sapwood – functional, lighter-colored wood nearer the outside of the stem
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Bark – protective outside covering of woody plants (cork, cork cambium, phloem) -cork cells are dead, and so rupture as the stem continues to expand (textured bark) Springwood – wide, thin-walled xylem produced when water is plentiful Summerwood – smaller, thicker-walled xylem produced when water is limited Annual ring – abrupt change between springwood and summerwood; used to estimate age of plant
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Transport nutrients and water -cohesion-tension theory – cohesion and adhesion allow the continuous column of water to move up plant - transpiration (water loss through stomata) occurs while plant exchanges gases Storing water and nutrients -occurs in parenchyma cells in cortex
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Support of leaves Translocation – movement of carbohydrates through the plant, from source (where the carbs are made) to sink (where the carbs are used); water follows the movement of carbs, causing pressure which keeps the carbs moving
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