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Angiosperm anatomy and physiology
Question ?
• What heading can be given to the following groups of words?
Question ?
• What is a vegetable?
• What is a fruit?
THM (take home message)
• Plants have organs too, just like animals.
• Asexual organs (vegetables)
• Sexual organs (fruits)
Plant Cell Types
• Differentiated by the type and thickness of the cell wall.
1. Parenchyma (soft tissue)
2. Collenchyma (glue tissue)
3. Sclerenchyma (hard tissue)
Parenchyma Cells
• Primary wall only.• Thin cell wall.• Alive when mature, • “typical" plant cell.
Functions
• Ps
• Storage
• "Filler" cells
• Cell division (mitosis)
Collenchyma
• Primary wall only.
• Wall is thickened, especially in the corners.
• Alive when mature.
Function
• Support of non-woody plant parts.
• Ex: veins, stems.
Sclerenchyma
• Secondary wall present.• Wall strengthened with
lignin.• Dead when mature.
Sclerenchyma Types
1. Fibers
2. Sclereids
3. Tracheids
4. Vessel Elements
Fibers
• Elongated thin cells used for support.
• Ex: Hemp fibers
Sclereids
• Used for hard dense areas and support.
• Ex: Nut shells, seed coats
Tracheids
• Spindle - shaped cells with pits in the cell walls.
• Used for water transportation.
Vessel
Fiber
Vessel Elements
• Wide stocky cells with pits in the side walls; lack end walls.
• Used for water transportation.
Plant Tissues
• Can be named by several methods:– Ex: Cell Location
Cell Origin Cell Function
Main Tissue Systems
1. Dermal
2. Vascular
3. Ground
Dermal Tissue
• Epidermis or "skin" of the plant.• Often has a cuticle, a waxy coating to prevent
water loss.• Functions:
– Prevent water loss.– Water absorption (root hairs).
Vascular Tissue
• Made of Xylem and Phloem.
• Functions:– Transport and support– Xylem - Water– Phloem - Food
Xylem
Phloem
Phloem
• Sieve Cell – alive when functioning, but lacks a nucleus.
• Companion Cell – alive, controls itself and the sieve cell.
Ground Tissue
• Tissue between the dermal and the vascular tissues.
• Functions:– "Filler" tissue– Ps– storage– support
Asexual Organs
1. Stem
2. Leaf
3. Root
Stem
• The main body of the portion above ground of a tree, shrub or herb.
• The ascending plant axis.
Stem Functions
• Support of other plant organs.
• Ps.
• Storage (water and food).
Leaf
• Lateral outgrowths of the stem axis.• Primary photosynthetic organs.• Function:
– Photosynthesis
– Storage
Root
• The descending axis of a plant, normally below ground.
• Functions:– Anchorage.
– Absorption of water and minerals.
– Storage.
Sexual Organs
1. Flowers
2. Fruits
3. Seeds
Flowers
• Modified leaves grouped together on a stem.
• Sexual reproductive organs.
• Function:– Sexual Reproduction
Fruit
• A mature ovary, sometimes including other floral parts.
• Function:– Seed dispersal– Seed protection
Seed
• Mature ovule containing the embryo and nutrient tissues.• Function:
– Dispersal unit in sexual reproduction.
– Johnny Appleseed–
“A far greater natural source of cyanide is the cassava root, a vegetable favored by many in Africa. (Westerners know this plant best as tapioca.) Drying, soaking, and baking cassava roots renders its cyanide precursor, linamarin, harmless, but if that process is not carried out properly the cassava can remain poisonous. “
A nice Question
• How does plant growth and animal growth differ ?
Animals
• Whole organism increases in size to a certain size...
Determinant Growth: grow to a certain size, then stop.
Plants
• Growth in specialized areas only.
• Indeterminant Growth: grow as long as they live because the specialized areas remain embryonic.
Plant Meristems• Perpetual embryonic
regions.• Zones for cell division.
Meristem Types
1. Apical growth in length. Primary growth.
2. Lateral/Cambiums growth in diameter. Secondary growth.
Comment
• Some tissues like Xylem may be Primary or Secondary depending on which meristem produced the cell.
• Ex:– Primary xylem from apical meristem– Secondary xylem from lateral meristem
• This is important when we speak of “wood”
Apical Meristem Types
1. RAM – Root Apical Meristem: primary growth of roots.
2. SAM – Shoot Apical Meristem: primary growth of shoots.
RAM
• Located at the tip of each growing root.
• Protected from the soil by the Root Cap.
RAM
Root Cap
• Protects RAM.
• Secrets a polysaccharide lubricant for root growth.
Root Zones
1. Cell Division - cells small and embryonic.
Cell Differentiation Begins in Primary Tissues (also known as primary
meristems)
2. Cell Elongation - cells elongate and start to mature.
3. Cell Differentiation - cells mature into final cell types.
Root Hairs
• Extensions of the epidermis to increase surface area for water absorption.
• Not a true tissue.• Comment - root hairs are very delicate and
must be continually replaced.
Root Hairs
RAM - Primary Tissues
1. Protoderm – matures into epidermis
2. Procambium – matures into vascular tissue
3. Ground Meristem – matures into ground tissue
Root Types
• Taproot - one main root.– Ex: carrot
• Fibrous Roots - many small roots of equal size.– Ex: grass roots
• Adventitious Roots– Roots that develop from other plant parts.– Ex: roots on stem cuttings, climbing roots
SAM Produces
1. Protoderm2. Procambium3. Ground MeristemComment – these tissues mature into the same
things as seen in RAM.
SAM Differences
• No "root" cap.
• Produces leaves as stem out-growths at the nodes.
• Has buds.
Buds
• Apical Meristems protected by modified leaves or bud scales (can see these NOW!!!).
• Axillary Buds
Branch Stems
• Develop from axillary meristems or axillary buds.
• "External" development.
Modified Stems
1. Rhizomes
2. Stolons
3. Tubers
4. Tendrils
Rhizome
• An elongated
underground horizontal stem.
• Ex: Iris, many grasses
Stolon
• An elongated
above-ground horizontal stem.
• Ex: Strawberries Airplane Plant
Tuber
• A much-enlarged, short,
fleshy underground stem tip.
• Ex: Dahlia, Potato
Tendril
• A slender coiling stem.
• Ex: Clematis and other climbing vines.
• Also occur on leaves of some plants
Leaves
• Stem outgrowths for Ps.
• Leaf Morphology:1. Gross
2. Fine
Gross Morphology
• Blade - the flattened portion of a leaf.
• Petiole - stalk of a leaf.
Blade
Petiole
Axillary Buds
Blade/Leaf Types
• Simple - 1 blade.
• Compound - Several blades.
Nodes and Internodes
• Node - stem area where a leaf and bud are attached.
• Internode - stem area between nodes.
Nodes
Internode}
Fine Morphology
• The tissues within a leaf.
1. Upper Epidermis
2. Mesophyll
3. Lower Epidermis
4. Veins
Upper Epidermis
• Cuticle present.
• Usually 1 cell layer thick.
• Cells w/o chloroplasts .
• Function: protects the mesophyll.
Mesophyll
1. Palisade upright cells.2. Spongy loosely organized
cells with air spaces.
• Function: major sites for Ps.
Epidermis
Epidermis
Lower Epidermis
• Cuticle present.
• Usually 1 cell layer.
• Cells w/o chloroplasts.
• Stomata present for gas exchange.
Stomata (Plant Breathing)
• Regulated by Guard Cells
Vein Structure
• Xylem: dorsal
• Phloem: ventral
• Often surrounded by bundle sheath cells for support.– What type of cells are these?– When have we talked about them before??
Xylem
Phloem
Bundle Sheath Cells
Collenchyma
Leaf Modifications
1. Tendrils: for support Ex: Peas
2. Bulbs: for food storage Ex: Onion
3. Insect Catching Ex: Carnivorous Plants
4. Flowers: thought to be modified leaves.
Tendrils Spines
Succulent Leaves Bracts
Other Modifications of Leaves
Stem Vascular Tissue
• Dicots – vascular bundles join together to make a ring. Often have secondary growth.
• Monocots – vascular bundles are scattered. No true secondary growth.
Secondary Growth
• Growth in diameter.
• Growth from lateral meristems or cambiums.
Cambium Types
1. Vascular – produces xylem and phloem.
2. Cork – produces “cork”…..(bark).
Vascular Cambium
• Location: between primary xylem and phloem.
• Produces: secondary xylem and phloem.
Fibers
Phloem
Vascular Cambium
Xylem
Fibers
Vascular Cambium: Cell Maturation
• Internal xylem
• External phloem
• The VC pushes the xylem and phloem apart from each other.
Result
• Newest xylem is next to the cambium.
• Oldest xylem is in the center of stem.
Result
• Newest phloem is next to cambium.
• Oldest phloem is under the epidermis.
Result
• Xylem accumulates over time.
• Phloem is destroyed by the outward growth and must be replaced yearly.
Cork Cambium
• Location: Cortex (external to the VC).
• Produces: Cork
• Comment – commercial cork is harvested from a Cork Oak.
Cork Cells
• Produced "outwardly" only.
• Covered with suberin and are dead when mature.
• Function – insulation and protection.
Vascular Cambium
Cork Cambium
Phloem
Xylem
Fibers
Cortex
Epidermis
Bark
• All tissues external to the VC.• Includes:
– Phloem (1 degree and 2 degree)– Cork – Cortex– Epidermis– Fiber cells
Wood
• Xylem tissue of a dicot stem.
• Comment – monocots don’t have VC and technically don’t produce true “wood”.
Xylem Growth
• Springwood - Large cells Rapid growth
• Summerwood - Small cells Slow growth
Annual Rings
• Formed by the growth difference between springwood and summerwood.
• Usually one produced per year.
Comment
• Ring size varies by climate and growing conditions.
• Rings can be used to date wooden structures.
Summer Wood
Spring Wood
One Year’s Growth
Monocots vs. Dicots
1. Seeds and embryos
2. Leaves
3. Stems
4. Roots
5. Flowers
Seeds and Embryos
• Dicots - no endosperm. - 2 cotyledons.
• Monocots - endosperm - 1 cotyledon
Leaves
• Dicots – netted veins.
• Monocots - parallel veins.
Stems
• Dicots - ring pattern - vascular cambium
• Monocots - scattered pattern - no vascular cambium
Roots
• Dicots – taproot. – xylem centermost tissue.
• Monocots - fibrous roots. - pith centermost
tissue.
Flowers
• Dicots – parts in 4's or 5's.
• Monocots – parts in 3's.