plant structure and function ch. 35
DESCRIPTION
Plant Structure and Function Ch. 35. http://www.uic.edu/classes/bios/bios100/labs/plantbod.gif. Morphology of a Flowering Plant. Root system and shoot system are connected by vascular tissue that is continuous throughout plant. Monocots vs. Dicots. - PowerPoint PPT PresentationTRANSCRIPT
Plant Structure and Function
Ch. 35
http://www.uic.edu/classes/bios/bios100/labs/plantbod.gif
Morphology of a Flowering Plant
• Root system and shoot system are connected by vascular tissue that is continuous throughout plant
Monocots vs. Dicots
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Nucleus
Plant Cell
Chloroplast
Cell Wall
Roots
• Functions– Anchor plant in the soil
– Absorb water and minerals
– Store food
Root Structure
Key
Dermal
Ground
Vascular
Epidermis
Root hair
Cortex Vascular cylinder
Zone ofmaturation
Zone ofelongation
Zone of celldivision
Apicalmeristem
Root cap
100 µm
Root Systems
Taproot Fibrous root
•Red mangrove growing in seawater
•Adventitious prop roots support and securely anchor this shrub in the mud and loose sand of tidal waters.
•Close-up view of prop roots •Numerous pores called lenticels which provide gas exchange and an additional source of oxygen for the submersed roots.
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Cortex
Epidermis
Developing lateral root
Vascular cylinder -xylem -phloem
Modified Roots
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Aer
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Stems
• Functions– Support
– Transport
– Storage
Monocot arrangement
Dicot arrangement
• Proximity of terminal bud inhibits growth of axillary buds (Apical dominance)
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Modified Stems
Storage leaves
Stem
Roots
Node
Root
Rhizome
Stolons—allow asexual reproduction
Bulbs—store food
Tubers—store foodRhizomes—horizontal stem
Leaves
• Leaf structure– Shape
– Size
– Edges
Leaf Structure
Mes
ophy
ll
Stomata
Modified Leaves
• Tendrils—allow plant to cling to support
• Spines—reduces water loss
Modified Leaves
• Storage—modified for water storage (succulents)
• Bracts—attracts pollinators
Modified Leaves
• Reproductive leaves—produce adventitious plantlets which fall off and take root
Tissue Systems
--cube-shaped, thin and flexible cell walls--function in photosynthesizing and storing organic products and wound healing
--elongated, thicker cell walls--cells grouped in strands or cylinders to support leaves and stems (parts that are still growing)
--cells have rigid, thick walls with lignin--at maturity, consists of dead cells--supports and strengthens plant
1. Ground System•Parenchyma
•Collenchyma
•Sclerenchyma
Tissue Systems
2. Vascular SystemXylem-Conducts water and minerals
from roots to plant-composed of dead cells that form water-pipe system
Phloem-Conducts food throughout plant-composed of living cells arranged into tubules
Water-conducting Cells of XylemPARENCHYMA CELLS
Parenchyma cells in Elodealeaf, with chloroplasts (LM) 60 µm
80 µmCortical parenchyma cells
Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM)
COLLENCHYMA CELLS
SCLERENCHYMA CELLS
SUGAR-CONDUCTING CELLS OF THE PHLOEM
WATER-CONDUCTING CELLS OF THE XYLEM
5 µm
Fiber cells (transverse section from ash tree) (LM)
25 µm
Sclereid cells in pear (LM)
Cell wall
Sieve-tube members:longitudinal view
30 µm
15 µm
Companioncell
Companioncell
Sieve-tubememberPlasmodesma
Sieveplate
Sieve plate with pores (LM)
Nucleus
Cytoplasm
Sieve-tube members:longitudinal view(LM)
Vessel elements withperforated end walls
Vesselelement
Tracheids
Pits
Tracheids and vessels(colorized SEM)
TracheidsVessel 100 µm
Sugar-conducting Cells of Phloem
PARENCHYMA CELLS
Parenchyma cells in Elodealeaf, with chloroplasts (LM) 60 µm
80 µmCortical parenchyma cells
Collenchyma cells (in cortex of Sambucus, elderberry; cell walls stained red) (LM)
COLLENCHYMA CELLS
SCLERENCHYMA CELLS
SUGAR-CONDUCTING CELLS OF THE PHLOEM
WATER-CONDUCTING CELLS OF THE XYLEM
5 µm
Fiber cells (transverse section from ash tree) (LM)
25 µm
Sclereid cells in pear (LM)
Cell wall
Sieve-tube members:longitudinal view
30 µm
15 µm
Companioncell
Companioncell
Sieve-tubememberPlasmodesma
Sieveplate
Sieve plate with pores (LM)
Nucleus
Cytoplasm
Sieve-tube members:longitudinal view(LM)
Vessel elements withperforated end walls
Vesselelement
Tracheids
Pits
Tracheids and vessels(colorized SEM)
TracheidsVessel 100 µm
Sheath of sclerenchyma
phloem
xylem
parenchyma
Tissue Systems 3. Dermal Tissue System
- Forms the outer covering of plants
•Epidermis-outer layer of cells covered by waxy cuticle•Stomata-structures that regulate passage of gases into/out of plant
Meristems: Primary GrowthGrowing region where cells actively divideApical meristems- grow in length at tips of stems and roots
Shoot apicalmeristems(in buds)
Vascularcambium
Corkcambium
Lateralmeristems
Primaryphloem
Periderm
Corkcambium
Secondaryxylem
Primaryxylem
Pith
Pith
Cortex
Secondary growth in stems
Secondaryphloem
Vascular cambium
Primary phloem
Primary xylem
Cortex
Primary growth in stems
Epidermis
Root apicalmeristems
Lateral meristems• Add thickness to woody
plants, a process called secondary growth
• Two lateral meristems– vascular cambium
adds layers of vascular tissue called secondary xylem (wood) and secondary phloem
– cork cambium replaces the epidermis with periderm, which is thicker and tougher
Primary Growth in Roots
Key
Dermal
Ground
Vascular
Epidermis
Root hair
Cortex Vascular cylinder
Zone ofmaturation
Zone ofelongation
Zone of celldivision
Apicalmeristem
Root cap
100 µm
Primary Growth in Shoots
Developingvascularstrand
Axillary budmeristems
0.25 mm
Leaf primordiaApical meristem
•Secondary growth occurs in stems and roots of woody plants but rarely in leaves
Vascular cambium•Produces secondary xylem and phloem
Cork cambium•Produces tough, thick covering for stems and roots
•Replaces epidermis
Anatomy of a Tree Trunk
• As a tree or woody shrub ages, the older layers of secondary xylem, the heartwood, no longer transport water and minerals
• The outer layers, known as sapwood, still transport materials through the xylem
Growth ring
Vascularray
Secondaryxylem
Heartwood
Sapwood
Vascular cambium
Secondary phloem
Layers of periderm
Bark
Growth, morphogenesis, and differentiation produce the plant body
• The three developmental processes of growth, morphogenesis, and cellular differentiation act in concert to transform the fertilized egg into a plant
Growth: Cell Division and Cell Expansion
• By increasing cell number, cell division in meristems increases the potential for growth
• Cell expansion accounts for the actual increase in plant size
The Plane and Symmetry of Cell Division
• The plane (direction) and symmetry of cell division are immensely important in determining plant form
• If the planes of division are parallel to the plane of the first division, a single file of cells is produced
Division insame plane
Plane ofcell division
Division inthree planes
Cell divisions in the same plane produce a single file of cells, whereas cell divisions in three planes give rise to a cube.
Single file of cells forms
Cube forms
Nucleus
The Plane and Symmetry of Cell Division
• If the planes of division vary randomly, asymmetrical cell division occurs
Unspecializedepidermal cell
An asymmetrical cell division precedes the development of epidermal guard cells, the cells that border stomata (see Figure 35.17).
Unspecializedepidermal cell
Asymmetrical
cell division
Guard cell“mother cell”
Unspecializedepidermal cell
Developingguard cells
The Plane and Symmetry of Cell Division
• The plane in which a cell divides is determined during late interphase
• Microtubules become concentrated into a ring called the preprophase band
Preprophase bandsof microtubules
Nuclei
Cell plates
10 µm
Genetic Control of Flowering• Flower formation involves a phase change from
vegetative growth to reproductive growth
• It is triggered by a combination of environmental cues and internal signals
• Transition from vegetative growth to flowering is associated with the switching-on of floral meristem identity genes
• Plant biologists have identified several organ identity genes that regulate the development of floral pattern
Normal Arabidopsis flower. Arabidopsisnormally has four whorls of flower parts: sepals (Se), petals (Pe), stamens (St), and carpels (Ca).
Pe
Se
Pe
Se
Pe
Se
Pe
Ca
St
Abnormal Arabidopsis flower. This flower has an extra set of petals in place of stamens and an internal flower where normal plants have carpels.
• The ABC model of flower formation identifies how floral organ identity genes direct the formation of the four types of floral organs
Sepals
Petals
Stamens
AB
CCarpels
C geneactivity
B + Cgene
activity
A + Bgene
activity
A geneactivity
A schematic diagram of the ABChypothesis