Chapter 34 - Stems - James Truong Chapter 34 Stem support...

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James Truong 1 Chapter 34 Stem – support leaves and reproductive structures o Internal support o New tissue generated (meristem) o Responsible for asexual reproduction Woody Twigs Buds – undeveloped embryonic shoots Terminal Buds – located at tip of stem Axillary buds (lateral buds) – located in leaf axils Bud scales – cover and protect dormant buds o Bud scale scars – left where bud scales fall off, when bud resumes growth Leaves o Node – area on stem where leaf is attached o Internode – region of stem between two nodes o Abscission (leaf) scar – where each leaf was attached to the stem o Bundle Scars – areas within a leaf scar where vascular tissue extended from stem leaf o Lenticels – sites of loosely arranged cells Allow oxygen to diffuse into interior of woody stem Herbaceous stems o Epidermis – protective layer covered by a water-conserving cuticle o Stomata – permit gas exchange o Xylem – conducts water and dissolved minerals o Phloem – conducts dissolved sugar o Cortex, pith, and ground tissue Function primarily for storage Basic tissue in herbaceous stems o Herbaceous eudicot stems Vascular bundles arranged in a circle (in cross section) Distinct cortex and pith o Monocot stems – vascular bundles scattered in ground tissue Dicot o In the vascular bundles of dicots, there are vascular cambium (allow for girth) o Some dicot stems have a phloem fiber cap which gives the stem a little extra strength for support Monocot o Random ground tissue and vascular bundles o Has a bundle sheath made of schlerenchyma to give it some extra strength for support Vascular Cambium – lateral meristem that produces secondary xylem (wood) and
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This note was uploaded on 12/02/2009 for the course SCI 90210 taught by Professor Durkka during the Spring '09 term at École Normale Supérieure.

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Chapter 34 - Stems - James Truong Chapter 34 Stem support...

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