Download - Plants Structure and Growth
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PLANTSSTRUCTURE
AND GROWTH
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FRUIT an organ that contains seeds, protecting
these as they develop and often aiding in their dispersal.
derived from ovaries, and other flower parts. Ovary walls thicken to form pericarp
Can be composed of up to 3 layers Exocarp Mesocarp Endocarp
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TYPES OF FRUIT Simple fruits – form from a simple ovary of a
single carpel, or from a compound ovary of several fused carpels Dry fruits
Achenes – close fitting pericarp around single seed Sunflowers
Grains – pericarp is fused to a single seed Wheat, corn
Nuts - thick woody pericarp fused to a single seed Walnuts, hazelnuts, acorns
Legumes - Pod that splits along two opposite sides Beans, peas, peanuts
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TYPES OF FRUIT CONT’D Simple fruits – cont’d
Fleshy Fruits – mesocarp forms flesh Drupes – 1 or 2 seeds, stony endocarp
Plum, peach Berries – 1 to many seeds, no stony endocarp
Tomatoes,, grapes, all citrus
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TYPES OF FRUIT CONT’D Compound/Aggregate Fruits
Develop from several individual ovaries of one flower Raspberries Strawberries...the inside is not actually fruit, but
flesh formed from the receptacle
Multiple fruits Formed from the fusion of many carpels belonging to
separate flowers pineapple
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FRUIT STRUCTURE AND FUNCTION FIG 10.8
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SEEDS AND YOUNG SHOOTS Germination occurs when conditions are
favorable Need: water, warmth, and oxygen
Many seeds remain dormant until certain conditions are met Inhibitors prevent germination, stimulators
trigger it High moisture levels, period of cold weather, fire
etc...
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SEEDS AND YOUNG SHOOTS Initial leaves to appear are the cotyledons
In dicots the cotyledons provide initial nutrition in monocots endosperm fills this role
First root to appear is the radical.
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FIG. 10.9AND 10.10
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PLANTS STRUCTURE All plant tissue develops from meristems
Specialized regions where cell division occurs
Apical Meristems are responsible for increased length Root Apical Meristem (RAM) Shoot Apical Meristem (SAM)
Protoderm develops epidermal tissue
Ground Meristem produces ground tissue
Procambrium develops vascular tissue
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FIG. 9.11B
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EPIDERMAL TISSUE Surrounds entire body of herbaceous and
young woody plants “Bark” develops after first year of growth
Bark is only a small portion of the new outer layer called periderm
Closely packed cells, designed to protect, and minimize water loss.
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EPIDERMAL TISSUE – CONT`D Specialized epidermal cells:
Root Hairs – Long projections from epidermal cells to increase surface area
Trichomes – hairs on stems, leaves and reproductive organs to protect against moisture loss
Guard Cells – surround microscopic holes on underside of leaves, able to open and close for gas exchange.
FIG. 9.4A
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GROUND TISSUE Forms the bulk of the plant
3 main cell types Parenchyma
Most abundant, look like ‘typical’ plant cell Least specialized, often contain plastids that store
products of photosynthesis.
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GROUND TISSUE CONT’D Collenchyma
Thickened cell wall, provide flexible support Strands in celery
Sclerenchyma Have thick secondary cell walls, mostly non-living,
provide support and structure Fibres – hemp, flax Sclerids – stones in peaches, grittyness of pears.
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GROUND TISSUE CONT’D
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VASCULAR TISSUE Located in
Vascular cylindar in roots Vascular bundles in stems Veins in leaves
Two primary tissues Xylem and Phloem
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VASCULAR TISSUE Xylem
Water and minerals from roots to leaves Two cell types, both non-living at maturity
Tracheids , Vessel elements FIG 9.6
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VASCULAR TISSUE Phloem
Sugar and other organic compounds, including - hormones, usually from leaves to roots
Two cell types Sieve tube members – have holes between to form
continuous tube, no nucleus Companion cells have nucleus, controls and maintains
life of both cells.
FIG 9.7
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LEAVES Photosynthetic organs of plants
Structure generally a flattened blade and a petiole that attaches to stem Simple leaves – single blade Compound leaves – many blades on one petiole
Adaptations Shade plants – broader leaves, darker in colour Xerophytes – no moisture, small needle-like leaves Tendrils to attach to objects Catch insects
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LEAF STRUCTUREFIG 9.8
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LEAF STRUCTURE Cuticle (upper and lower)
Waxy layer prevents moisture loss
Epidermis (upper and lower) Outer layer of cells, provides structural support,
generally no chloroplasts
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LEAF STRUCTURE CONT’D Pallisade Mesophyll
Brick like cells, stacked on end Primary site of photosynthesis
Spongy Mesophyll Irregular cells, Loosely packed, lots of air space
Promotes gas exchange Veins are held within this layer
Veins Vascular tissue surrounded by bundle sheath cells
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LEAF STRUCTURE CONT’D Stomata
lower epidermis, regulates gas exchange and water levels
Opening surrounded on each side by two large guard cells. Water levels control opening and closing
absorb water swell stomata opens. lose water relax stomata close
During the heat of the day, water levels decrease, stoma stay closed Helps to decrease water loss
At night, water levels are able to rise, stoma open allowing leaves to release excess water, exchange Carbon Dioxide and Oxygen.
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FIG 9. 23