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Angiosperms – flowering plants
• The angiosperms are seed-bearing vascular plants
• In terms of distribution and diversity, they are the most successful plants on Earth
• The structure and function of this plant group help explain its success
Flowering Plant Life
Cycle Double fertilization Meiosis Meiosis
microspores
Female gametophyte
pollination
Mitosis without cytoplasmic division
Two sperms enter ovule
Diploid
Haploid
Plant Life Histories
• Annuals complete life cycle in one
growing season
• Biennials live for two seasons; flowers
form in second season
• Perennials grow and produce seeds
year after year
Shoot System
Root System
Root system
- anchors the plant
- penetrates the soil and absorbs water and minerals
- stores food
Shoot system
- produces sugars by photosynthesis
- carries out reproduction
Shoot and Root Systems
Plant Tissue Systems
VASCULAR TISSUES
GROUND TISSUES
SHOOT SYSTEM
ROOT SYSTEM
EPIDERMIS
• Ground tissue system
• Vascular tissue system
• Dermal tissue system
Meristems – Where Tissues Originate
• Regions where cell divisions produce plant growth
• Apical meristems– Lengthen stems and roots– Responsible for primary growth
• Lateral meristems– Increase width of stems– Responsible for secondary growth
Apical Meristems
activity atmeristems
new cellselongateand start todifferentiateinto primarytissues
procambium primary vascular tissues
protoderm epidermis
Cells that form at apical meristems:
ground meristem ground tissues
Lengthen shoots and roots:SAM and RAM
Lateral Meristems
vascular cambium secondary vascular tissues
periderm cork cambium
thickening
Increases girth of older roots and stems
Cylindrical arrays of cells
Parenchyma: A Simple Tissue
• Comprises most of a plant’s soft primary growth
• Cells are pliable, thin walled, many sided
• Cells remain alive at maturity and retain capacity to divide
• Mesophyll is a type of parenchyma that contains chloroplasts
Collenchyma: A Simple Tissue
• Specialized for support for primary tissues
• Cells are elongated, with walls (especially corners) thickened with pectin
• Makes stems strong but pliable
• Cells are alive at maturity
Sclerenchyma: A Simple Tissue
• Supports mature plant parts• Protects many seeds• Cells have thick, lignified walls and are dead
at maturity• Two types:
– Fibers: Long, tapered cells– Sclereids: Stubbier cells
Xylem
• Conducts water and dissolved minerals
• Conducting cells are dead and hollow at maturity
vessel membertracheids
Phloem: A Complex Vascular Tissue
• Transports sugars
• Main conducting cells are sieve-tube members
• Companion cells assist in the loading of sugars
sieve plate
sieve-tubemember
companioncell
Epidermis: A Complex Plant Tissue
- Covers and protects plant
surfaces
- Secretes a waxy,
waterproof cuticle
- In plants with secondary
growth, periderm replaces
epidermis
Monocots and Dicots – same tissues, different features
Parallel veinsNetlike veins
3 pores1 pore
4 or 5 floral parts
3 floral parts
1 cotyledon 2 cotyledons
Vascular bundles dispersed
Vascular bundles in ring
Shoot Development
ground meristem
primary xylempithprocambriumcortex
procambriumprotoderm
shoot apicalmeristem
primary phloem
Bud = undeveloped shoot of meristematic tissue
Internode
Leaves
Axillary bud at node
Longitudinal section of terminal bud
Internal Structure of a Dicot Stem
- Outermost layer is epidermis
- Cortex lies beneath epidermis
- Ring of vascular bundles separates the cortex from the pith
- The pith lies in the center of the stem
Internal Structure
of a Monocot
Stem
• The vascular bundles
are distributed
throughout the ground
tissue
• No division of ground
tissue into cortex and
pith
Dicots
Dicots and Monocots have different stem and root anatomies
Ground tissuesystem
Vascular tissue system
Dermal tissuesystem
Monocots
Adapted for Photosynthesis
• Leaves are usually thin – High surface area-to-volume ratio
– Promotes diffusion of carbon dioxide in, oxygen out
• Leaves are arranged to capture sunlight– Are held perpendicular to rays of sun
– Arrange so they don’t shade one another
Leaf StructureUPPER
EPIDERMIS
PALISADEMESOPHYLL
SPONGYMESOPHYLL
LOWEREPIDERMIS
one stoma
cuticle
O2CO2
xylem
phloem
Mesophyll:Photosynthetic Tissue
• A type of parenchyma tissue
• Cells have chloroplasts
• Two layers in dicots
– Palisade mesophyll
– Spongy mesophyll
Leaf Veins: Vascular Bundles
• Xylem and phloem –
often strengthened with fibers
• In dicots, veins are netlike
• In monocots, they are parallel
Root Structure
• Root cap covers tip
• Apical meristem produces the cap
• Cell divisions at the apical meristem cause the root to lengthen
• Farther up, cells differentiate and mature
root apical meristem
root cap
Internal Structure of a Root
• Outermost layer is epidermis
• Root cortex is beneath the epidermis
• Endodermis, then pericycle surround
the vascular cylinder
• In some plants, there is a central pith
Root Hairs and Lateral Roots
• Both increase the surface area
of a root system
• Root hairs are tiny extensions
of epidermal cells
• Lateral roots arise from the
pericycle and must push
through the cortex and
epidermis to reach the soil
newlateralroot
Secondary Growth
• Occurs in perennials
• A ring of vascular cambium produces
secondary xylem and phloem
• Wood is the accumulation of these
secondary tissues, especially xylem
Woody Stem
periderm (consists ofcork, cork cambium,and secondary cortex)
secondaryphloem
BARK
HEARTWOOD SAPWOOD
vascular cambium
Annual Rings
• Concentric rings of secondary xylem
• Alternating bands of early and late wood
• Early wood– Xylem cells with large diameter, thin walls
• Late wood– Xylem cells with smaller diameter, thicker
walls
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