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Published byPercival Patterson Modified over 6 years ago
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Monocot Roots large vascular cylinder in center
ring pattern of xylem (large openings) and phloem tissue surrounded by endodermis vascular cylinder surrounded by fairly thick cortex fibrous root system
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Dicot Roots small vascular cylinder in center;
large openings are xylem tissue surrounded by smaller phloem cells in a ‘star’-shaped pattern very thick cortex tap root system
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Stems support leaves transport materials between roots and leaves (e.g. water, sugar) storage of food (e.g. sugars) may be photosynthetic Woody stems: found in trees and shrubs, don’t die back in winter, annual rings used to determine age Herbaceous stems: green in colour, contain chlorophyll, undergo photosynthesis, die back in winter
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Monocot Stems vascular bundles scattered in fundamental (ground) tissue
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Dicot Stems vascular bundles in ring pattern in fundamental tissue
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HERBACEOUS STEMS Vascular Bundles collection of xylem and phloem xylem is closer to the inside and phloem the outside phloem xylem
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Vascular Cambium between the xylem and the phloem this is where new xylem and phloem are made vascular cambian
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Woody stem Heartwood dead cells fill with materials that harden Sapwood active xylem that transports water & minerals sapwood heartwood
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new layers of xylem & phloem cells allow stem to grow in width
Vascular Cambium new layers of xylem & phloem cells allow stem to grow in width Cork dead phloem cells containing chemicals Bark outer protective layer, also dead phloem vascular cambian cork bark
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Annual rings more xylem forms in wet months (light band) than in dry months (dark band) Dry months Wet months
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bark annual rings cambium pith rays heartwood sapwood
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Both herbaceous and woody stem types are found in monocots and dicots
However there is no secondary growth (stem diameter increases) for woody monocot stems and thus no “tree rings” to use to determine their age. Palm tree cross-section showing no annual rings
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Modified Stems Tuber: modified for food storage, grow underground (e.g. potato) Bulb: underground stem with layers of modified leaves (e.g. onion) Corm: enlarged, underground stem, with scaly leaves (e.g. gladioli) Rhizome: thick, fleshy underground stems (e.g. irises) tuber bulb corm rhizome
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Leaves main function is photosynthesis
(carbon dioxide + water --> glucose + oxygen) green colour due to chlorophyll pigment which absorbs energy and reflects green a. Leaves tend to be broad and flat to increase the surface area exposed to sunlight. b. Photosynthesis occurs primarily within the mesophyll cells in the interior of the leaf. The vascular bundles carry water to the leaves and carry the product of photosynthesis, sugar, to other parts of the plant. It is the pores called stomata, mostly on the underside of leaves, that allow for the passage of gases in and out of the leaf. c. Guard cells of the stomata control the opening and closing of the stomata. When sunlight shines on the leaf during the day, the guard cells engorge with water that makes them bow apart, thus opening the stomata.When sunlight is reduced, water flows out of the guard cells, causing the stomata to close.
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Cuticle: waxy layer that prevents water loss Epidermis: Outer layer of cells that protects the leaf
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Palisade Layer Main site of photosynthesis as cells have many chloroplasts Spongy Layer Some photosynthesis, but lots of air spaces [for CO2]
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Vein Xylem & phloem to bring water & remove sugars Guard Cells Stoma(ta) Small openings that allow air in and out of leaf Cells that swell when filled with water to open stoma
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Monocot Leaves veins (vascular bundles) are spaced evenly along leaf
leaves tend to be long & narrow stomata allow exchange of gases
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Dicot Leaves veins are large, spaced randomly through leaf
leaves are broad, have many parts stomata found mostly along bottom of leaves
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Leaf Adaptations spines (e.g. cacti and pine needles) have thick waxy cuticle to prevent water loss thick leaves (e.g. jade plant) are used for water storage aquatic plants (e.g. water lily) must have stomata on upper surface of leaf only for gas exchange
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Drawing some plant parts
Draw a cross section of each the following: Monocot root and dicot root (using the ‘wedge’) Monocot stem and dicot stem (using the ‘wedge’) Monocot leaf and dicot leaf (drawing everything)
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Name of Specimen (stain used if known)
Magnification Number “Wedge” is large enough to show detail of pattern “Wedge” includes centre of field of view High detail inside wedge including stippling Low detail outside of wedge to show pattern Wedge is in centre or on right side of field of view All plants have vascular bundles. (VERY IMPORTANT TO SHOW!!!) THE “WEDGE” METHOD:Used when specimens take up the entire field of view or to show repeating patterns in a specimen.
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