Download Plant Growth and Development

Hort I
PLANT GROWTH AND DEVELOPMENT
Primary Plant Parts and Functions
Plant Parts and Function
 Terminal bud (apical bud)
–
 Main area of growth on a
plant
 Produces all the
differentiated tissues,
including vegetative and
reproductive organs
 Apical dominance inhibits
the growth of axilary buds
by producing auxins
 Auxins – hormones that
prevent lateral growth
Plant Parts and Function
 Axillary (lateral) bud
 Forms in the axil
 Develop from the
nodes
 Capable of
developing into a
branch, shoot or
flower
 Axil
 Angle between the
upper stem of the
plant and a leaf
branch
Primary Plant Parts and Functions
 Node
 Part of a stem
from which a
leaf, branch or
aerial root grows
Primary Plant Parts and Functions
 Internode
 Part of the
stem between
two nodes
Primary Plant Parts and Function
 Stem
 Main structural
part of the plant
 Has nodes and
internodes
Primary Plant Parts and Function
 Flower
 Reproductive part of
the plant
 Attracts pollinators
to insure seed
production
 Flower stem
 Supports the flower
Primary Plant Parts and Function
 Lateral
branch/shoot
 Branches that
grow off the side
of the stem
Primary Plant Parts and Function
 Leaf
 Apex – end opposite the






petiole
Margin – edge of leaf
Blade – face of leaf
Vein – Structural Framework
of Leaf
Petiole – attaches the blade
to the stem
Leaflet – looks like a leaf, but
has no petiole (compound
leaves)
Stipules-growths at the base
of the petioles
Hardwood Plant Parts and Functions
 Leaf scar Mark left on a branch
after a leaf falls
 Terminal bud
scar/annual rings
 Marks left from growth in
the previous year
 Bundle scars
 markings within a leaf
scar at the location where
vascular bundles were
broken as the leaf petiole
detached from the twig.
Stem Structures
 Epidermis
 Outer layer of wax coated cells
that provide protection
 Cuticle –protective waxy
coating produced by the
epidermis;
thicker on succulents
 Cortex
 Primary stem tissue; epidermis is
outside; phloem is inside
Vascular Bundles
 Xylem
 Transports water and nutrients
 Provides structure
 Phloem
 Tissue that moves sugars
 Cambium
 Single celled layer of meristematic
(dividing) tissue adding width to the
stem
 Forms phloem towards the outside
and xylem towards the inside
 Pith
 Center of dicot plants
 Rigid xylem wood fiber
Primary Plant Parts and Functions
 Roots
 Internally same as stems
 Three types
 Tap root
 Fibrous roots
 Adventitious roots
Underground Stem Modifications
 Rhizome
 Horizontal, underground stem
 Capable of producing shoot and
root systems of a new plant
 Allows for vegetative
(asexual)reproduction
 Enables a plant to survive annual,
unfavorable season (perennate)
underground
Rhizome
 In some plants, the
rhizome is the only stem;
only leaves and flowers
are readily visible (water
lillies, some ferns)
Underground Stem Modifications
 Tuber
 Short, thickened, mostly
underground stem
 has minute scale leaves, each with a
bud that has the potential
for developing into a
new plant.
Tubers
 Potato, jerusalem
artichoke, yams,
caladium
Tuberous Roots
 Tuberous roots (not the same as
tubers)
 Bulbets form at the base of the
stem
 Root structure, not an underground
stem – Dahlias and Begonias
 Sweet potatoes are a tuberous root
Underground Stem Modifications
 Corm
 A round, swollen mass of storage




tissue at the base of the stem
Has a basal plat e from which the
roots grow
Develops small, peas sized
cormels around the top of the old
corm
Cormels may be planted and will
grow into a new corm
Gladiolus, crocus, tarot
Underground Stem Modifications
 Bulb
 Made up of five parts
 Basal plate; bottom from
which root s grow
 Primary storage
tissue/fleshy scales
 Shoot from which the new
buds grow
 Lateral buds – develop into
bulb-lets
 Tunic – protective coating
Bulb
 Two sub-types of bulbs
 Bulbs that have a papery covering, or tunic, are
called tunicate bulbs -daffodil.
 Bulbs that lack this protective covering
(imbricate/nontunicate) must be kept moist at all
times – lily
Sub-aerial Stem Modifications
 Offset
 A shoot that develops
laterally at the base of
a plant, often rooting
to form a new plant.
Sub-aerial Stem Modifications
 Stolon/runner
 Stems which grow at the soil surface, or
below the ground and form new plants
at the ends or at the nodes
Sub-aerial Stem Modifications
 Sucker
 A basal shoot, root sprout, adventitious shoot,
water sprout
 A shoot or cane which grows from a bud at the
base of a tree or shrub
 May grow from the roots
 Takes the form of a singular plant
Aerial Stems
 Tendril
 Specialized stem, leaf or petiole
with a threadlike shape
 Used by climbing plants for
support and attachment
 Can photosynthesize (no lamina or
blade)
 can be formed from modified
shoots, modified leaves, or
auxiliary branches
Aerial Stems
 Thorn
 Modified branches/stems
 Protect the plant from
herbivores
Aerial Stems
 Phylloclade/cladode
 Flattened green
stems that serve as
PSN organ
 Looks like a leaf
Aerial Stems
 Bulbil
 Stem modifications
that aid in plant
reproduction
Flower
s
 The purpose of flowers is to produce seed
 A plants purpose in life is to reproduce.
Parts of a Flower
 Pistil (Carpel)
 Female part of flower where
egg cell originates
 Stigma
 Upper part of pistil that
catches pollen
 Style
 Supports stigma
 Contains pollen tube
 Ovary
 Produces ovules which develop
into seeds
Parts of a Flower
Parts of a Flower
 Stamen
 Male part of flower
where pollen
originates
 Filament
 Supports the anther
 Anther
 Bears the pollen
Accessory Organs
 Corolla
 Petals of the flower
Accessory Organs
 Calyx
 Sepals of the flower
Accessory Organs
 Pedicel
 Stalk of an individual
flower
 Peduncle
 Attached to the
pedicel of many
flowers or a single
flower
Types of Flowers
 Complete
 Stamens, pistils, petals
and sepals
 common in dicots
Types of Flowers
 Incomplete
 Has stamens and
pistils
 Petals or sepals or
both are missing
 Common to monocots
Types of Flowers
 Perfect Flower
 Has both stamens
and pistils on the
same flower
Types of Flowers
 Imperfect flowers
 Has either stamens or
pistils
 Not both on the same
flower
Types of Flowers
 Staminate
 Only male flower parts
 Pistillate
 Only female flower parts
Types of Flowers
 Monecious
 Staminate and pistillate flowers found on the same plant
 Corn, cucumbers, squash, melons, pumpkins
 Dioecious
 Staminate and pistillate flowers on separate plants
 Spinach, asparagus, some fruit trees
Types of Fruits
 Fleshy fruits
 Pome
 Outer, fleshy
layer developed
from calyx and
receptacle
 Ovary forms a
leathery core
containing
seeds
 Pear, apple
Types of Fruits
 Drupe
 Ripened ovary
becomes twolayered outer
forming a pit
enclosing a
seed
 Cherry, peach,
plum
Types of Plants
 Berry
 Ovary is fleshy and
unusually juicy
 Contains several
seeds
 Tomato, grape,
cucumber
Types of Fruits
 Aggregate Fruit
 Several pistils in a
single flower form
compound fruit
 Strawberry,
raspberry,
blackberry
Types of Fruits
 Multiple Fruit
 Several clusters
of flowers form
compound fruit
 Mulberry,
pineapple, fig
Types of Fruits: Dry
 Pod
 Thin ovary wall
 Single chambered,
contains several seeds
 Splits along line when ripe
 Pea, bean, milkweed
 Capsule
 Several chambers and
seeds in ovary
 Iris, lily, cotton, poppy
Types of Fruits: Dry Closed
 Nut
 Ovary wall is hard
 Encloses one seed
 Oak, acorn, walnut
Types of Fruits: Dry Closed
 Achene
 Ovary wall isn’t
fastened to seed
 Dandelion, sunflower
Types of Fruits: Dry Closed
 Grain
 Ovary wall is thin and
fastened securely to
a seed
 Corn, wheat, oats
Types of Fruits: Dry Closed
 Samara
 Winged fruit
 Wing attached to the
ovary wall
 Maple, elm, ash