Plant Structure, Reproduction, and Development
Angiosperms
• Cotyledons – embryonic leaves• Monocot – one embryonic leaf• Dicot – two embryonic leaves• Differences between Monocots & Dicots
– Veins are parallel /branched– Vascular bundles complex /ring– Leaves arranged in multiples of 3 /multiples of 4 or 5– Fibrous roots /taproot
Figure 31.2
SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS
MONOCOTS
Onecotyledon
Main veins usually parallel
Vascular bundles incomplex arrangement
Floral parts usuallyin multiples of three
Fibrousroot system
Twocotyledons
Main veins usually branched
Vascular bundles arranged in ring
Floral parts usually in multiples of four or five
Taprootusually present
DICOTS
Angiosperms
• Most angiosperms are dicots
• This group includes shrubs, trees (except conifers), and many of our food crops
• Monocots include orchids, bamboos, palms, lilies, and grains and grasses.
Plant Body
• Root system – anchors the plant into the soil
– Roots have root hairs – outgrowth of epidermal cells
– Shoot system – part of plant above groundstems – support leaves and groundednodes – points where leaved are attachedleaves – main site of photosynthesisterminal bud – node at tip of plant; responsible for growth lengthwise; apical dominance (inhibits growth of axillary buds)axillary buds – located in angles formed by the leaf; usually dormant; causes the plant to become bushy
Figure 31.3
Terminal bud
Blade
PetioleAxillary bud
Leaf
Stem
Taproot
SHOOTSYSTEM
ROOTSYSTEM
Roothairs
Internode
Node
Flower
Modified Roots and Shoots
• Modified taproots – sweet potatoes, sugar beets, & carrots/ stores starch– Uses this stored sugar
source for active growth and producing flowers and fruit
• Modified Stems– runner – horizontal stem– rhizomes – horizontal stem
underground– tubers – white potatoes that
are at the end of rhizomes that store sugar
STRAWBERRYPLANT
POTATOPLANT
IRISPLANT
Runner
TuberTaproot
Rhizome
Rhizome
Root
Modified Roots and Shoots
• Modified leaves– Grasses have no petioles– Celery have enormous petioles that we eat– Tendrils have coiled tips which aid in climbing– Cactus have spines
Plant Tissue Systems
• Epidermis– Covers and protects– First line of defense– Cuticle is the waxy substance that helps
plants to retain water
• Vascular System– xylem/phloem – transports water and
nutrients– support
Plant Tissue System
• Ground Tissue System– Filling spaces, bulk– Parenchyma, collenchyma, sclerenchyma– Photosynthesis, storage, support
Plant Tissue System
• Roots– Epidermis
• Covers roots• Entrance for water and nutrients• May form root hairs• No cuticle
– Ground tissue• Cortex – parenchyma, store food• Endodermis – selective barrier, thin layer of cells decides what
passes between vascular tissue and cortex– Vascular Bundles
• xylem – spokes of wheel• phloem – fills in wedges between spokes
Figure 31.6B
Xylem
Phloem
Epidermis
VASCULARTISSUESYSTEM
GROUNDTISSUESYSTEM
Cortex
Endodermis
Plant Tissue System
• Leaf– Epidermis
• Covered by cuticle• Small pores called stomata• Surrounded by guard cells
– Ground Tissue• Mesophyll composed of parenchyma cells and chloroplast• Air located in spaces between cells
– Vascular System• Vein – composed of xylem and phloem surrounded by
parenchyma cells
Figure 31.6D
Plant Tissue System
• Stem– Epidermis
• Thin layer of cells• Covered by cuticle
– Ground Tissue• Dicot - 2 parts / Monocot – 1 part (ground tissue)
– Pith – food storage– Cortex – fills spaces
– Vascular Tissue• Occurs in vascular bundles
– Dicot – ring– Monocot - random
Figure 31.6C
Plant Cells
• Three main differences between animal cells and plants cells are – Cell wall– Central vacuole– chloroplasts
Figure 31.5A
Plant Cells
Five Major Types of Plant Cells 1. Parenchyma cells – most abundant type
• Remain alive at maturity• Primary cell wall (thin)• Function in food storage and photosynthesis• Multisided
2. Collenchyma cells
primary cell wall (thick)
alive at maturity
provide support in plants that are still growing
Figure 31.5B
Primarywall(thin)
Pit
Parenchyma Cells
Plant Cells
3. Sclerenchyma cells – Rigid secondary walls– Hardened with lignin– Found in regions that is not growing– Dead at maturity– Two types of sclerenchyma cells
• Fiber – long and slender and occurs in bundles; hemp fibers make rope
• Sclereid – stone cell; short, irregular shaped secondary wall; found in nutshells and sead-coats
Figure 31.5D
Pits
Primarywall
FIBER
Secondarywall
Fibercells
Sclerenchyma Cells
Sclereids (stone cells)
Figure 31.5D continued
Secondarywall
Sclereidcells
Primarywall
Pits
SCLEREID
Sclerenchyma Cells
Plant Cells
4. Water-Conducting cells – Rigid, lignin-containing
secondary cell walls– Cells are dead at maturity– Hollow in the middle– Functions in support
Two types of water-conducting cells
1. Tracheids – long cells with tapered
ends
2. Vessel Elements – wide, short cells
Pits
Vessel element
Tracheids
PitsOpeningsin end wall
Plant Cells
5. Food – Conducting cells (sieve tube members)
-arranged end to end
- thin primary walls with no secondary wall
-alive at maturity
-transports sugars and minerals
-sieve plates – located at the ends of the sieve tube members
Sieve plate
Companioncell
Cytoplasm
Primarywall
Sieve Tube Members
Primary Growth
• Indeterminate growth – continue to grow as long as they live– Annuals – wheat, corn, rice– Biennials – beets, carrots– Perennials – trees, shrubs, grasses
Primary Growth
• Apical meristem – lengthwise growth
• Root cap – protects apical meristem in roots
• Two functions of root apical meristem– Replaces cells of root cap– Produces cells for primary growth
Primary Growth
• Three regions of roots– Epidermis (outermost)– Cortex (bulk)– Vascular tissue
• Elongation – uptake of water– cellulose fibers extend (accordion)– forces roots into soil
• Differentiation – caused by master gene; causes unspecialized cells to specialize
Figure 31.7B
Vascularcylinder
Cortex
Epidermis
Root hair
Cellulosefibers
Apical meristemregion
Rootcap
DIF
FE
RE
NT
IAT
ION
EL
ON
GA
TIO
NC
EL
LD
IVIS
ION
Primary Growth
• Three Zones– Cell division– Elongation– Differentiation
• The angiosperm flower is a reproductive shoot consisting of– sepals– petals– stamen– carpels
Figure 31.9A
Stigma
Ovary
Carpel
Anther
Petal
Ovule Sepal
Stamen
Flower Reproduction
Fertilization of an Angiosperm
• Formation of a pollen grain– Cells that make pollen grains are located in
the anther– Meiosis- four haploid spores that eventually
form two haploid cells called a tube cell and a generative cell
– Wall forms around the two cells known as a pollen grain
– Animals, wind, and water transport pollen grain (male gametophyte)
Fertilization of an Angiosperm
• Formation of an Egg Cell– Megaspore mother cell – forms 4 haploid
megaspores and three degenerate– Surviving megaspore enlarges/ mitotic
division– End Result – One large cell with two haploid
nuclei and six smaller cells.– One of the six smaller cells is the haploid
egg.
Pollination
Sugar/enzymes on stigma causes tube cell to grow and form pollen tube
• Both cells (generative cell and tube cell) travel to embryo sac
• Generative cell forms two sperm cells• One sperm cell fertilizes the nucleus with the
polar nuclei (triploid nucleus/3n)
Pollination
• One sperm cell fertilizes egg cell (diploid nucleus/2n)
• Triploid forms endosperm/functions to nourish embryo (popcorn)
• Flowering plants (double fertilization)• Alternation of generations
– Haploid – female gametophytes (ovules/egg), male gametophytes (generative cell/sperm)
– Diploid – sporophyte (plant/flower); produces haploid spores by meiosis