Transcript Modified Stems

What is this???
Plant Structures
Leaves
Stems
Roots
Flowers
What Are primary
parts of plants?
Leaves
Stems
Roots
Flowers
What are the
functions of leaves?
 Capture light
 Exchange gases
 Provide a site for photosynthesis
 Some leaves store food and water
 Some form new plants and provide
support
What is
photosynthesis?
It is a process by which plants
combine water and carbon
dioxide in the presence of
chlorophyll and sunlight and
produce carbohydrates and
release oxygen.
Why is photosynthesis
important?
 Light is the most important
source of energy for living
things. Photosynthesis converts
light into nutrients that can be
used by plants and animals.
 Releases oxygen
Photosynthesis
6CO2 + 12H2O + sunlight --->
6O 2 + C6 H12O 6 + 6H2 O
There are two parts of
photosynthesis--the light and
dark reactions.
The light reactions produce
chemical energy from light.
The dark reactions convert
carbon dioxide into
carbohydrates.
Leaves in gas
exchange
 Oxygen, Carbon Dioxide, and
Water exchanged from Stomata
 Pores open in day to transpire
H2O and allow gases to enter
 Close during dry conditions to
prevent H2O loss.
External Parts of Leaves
Petiole- Stalk of leaf that
attaches to stem
Midrib- Main vein of vascular
tissue
Blade- Photosynthetic site of
leaf
Stomata
Openings on the
epidermis
allows air into leaf
allows H2O and oxygen
out of leaf
Stems
 Water and mineral transport by
capillary action and cohesion to
the leaves.
 Transport food to the roots
 Gas exchange
 Produce and support new
leaves, branches, and flowers
Internal parts of stem
Phloem
Xylem
Cambium
Pith
Cortex
Functions
Phoem-Sugar and
carbohydrates to roots
Xylem- Water and nutrients
Cambium- Growing part of
stem
Function Cont’
Pith-Occupies the central
area of the stem
Cortex- Composed of
several layers of thick-walled
cells
External parts of stem
Buds
Nodes
Internodes
Modified Stems
 Rhizomes- Horizontal underground
stems(Bermuda Grass
 Stolons- Horizontal above ground
stems(strawberries)
 Tubers- Greatly enlarged tip of
underground stem
Cont.
 Bulbs- budlike structure
consisting of a small stem
(onion)
 Corms- Fleshly leaves
underground stems with few
nodes(gladiolus)
Functions of Roots
 Anchor plants in soil
 Absorb water and nutrients
 Some store reserves for future
uses(Potato)
 Propagation
Taproots
 Advantages
 Disadvantages
 Penetrates
 Difficult to
deeper
 Obtain water
from other
levels
 Anchor plant
remove or
harvest
 do not stabilize
well
Fibrous
 Advantages
 Disadvantage
 Shallower,
 Less drought
better for
fertilization &
Water
 Stabilize in soil
better
resistant
 Tend to get
exposed during
cultivation
Primary Roots
 Grow
down into the soil and
may branch repeatedly into
lateral roots
 Taproot is a primary root
Lateral Roots
 Called Secondary roots
 grow horizontally away from the
primary root
 Some grow downward
Adventitious
 Came from stems or leaves
instead of another root
 Prop root of corn and grapes
are examples that give support
Fibrous Root
 Root structures in which the
primary and lateral roots
develop equally so there is not
a definite taproot.
Storage Roots
 Are structures such as those of
carrots and sweet potatoes
which are used for food
storage.
What do stems and roots
have in common?
 Both have xylem and phloem
cells for transport.
Male flowers and their
parts and functions.
 Stamen- has two parts- filament
and antherFilament- supports
the anther
 Anther- Produces pollen grains
Female parts and
their functions
 Ovule-develops into a seed
 Ovary- surrounds the ovule, later
becomes the fruit
 Style-supports the stigma
 Stigma- receives the pollen grain
 Pistil- All three female parts
together
Other parts of flower
 Receptacle- enlarged part of the
flower stalk where floral part is.
 Sepals- outer protective parts of
buds
 Petals- the colored part of the
flower used to attract insects
Complete Flower
 Both have Male and Female
parts
Incomplete Flowers
 Have either male or female
parts but not both
Monoecious
 Plants that have male and
female flower parts on separate
plants
Dioecious
Have both parts on the
same plant.
Pollination
 The transfer of pollen from one
anther to anther stigma.
 Two ways- self-pollination &
Cross-pollination
 Bees and Wind
The End