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th
6
Grade - plants
Purpose of plants
 Why do we need plants???
Leaves
 Purpose of leaves
 to produce food for plant
Needs of Leaves
Needs of Leaves:
 Water – from the ground
 Air – through the stomata (stoma) – little
holes in the bottom of the leaf
 Light – from the sun
Photosynthesis
 Photosynthesis – The chemical process
by which green plants produce food
 without photosynthesis plants cannot
grow
 Plants are the only living things that can
make their own food
 All life depends on plants
Definitions of
photosynthesis
 Chlorophyll – the pigment (coloring) that
makes plant green
 Chloroplasts – tiny packages of chlorophyll
contained in the cells of the leaf
 Glucose – a type of sugar that plants need to
live
 Leaves also make proteins and vitamins for
plant’s nourishment
Process of Photosynthesis
Parts of a leaf
VEIN
MIDRIB
STEM
Parts of a leaf
Parts of a leaf
 Stem – joins the leaf to a plant
 Vein – spread outward from the stem, transport
liquids and reinforce structure
 Midrib – large vein that runs straight up the
middle of the leaf
 Color – most food making cells (top)
 Cuticle – waxy covering that coats the skin of a
leaf and prevents water from escaping
Special Leaves
 Twining climbers
 Vines – plants that climb upwards as they
grow by clinging to tall objects
 Tendrils – special leaves that are the hands
with which a vine grasps a support structure
Special Leaves
 Tasty storage space
 These leaves grow partially below the
ground. They insulate the plant in the cold.
 Many layers of lower leaves that remain
below the ground for a bulb. Ex. onion
Special Leaves
 Prickly Protection
 Spines – of cacti are special leaves that
contain no chlorophyll
 Spines protect the water storing stem of the
cactus plant
Special Leaves
 Insect Eaters
 “insectvorous” insect eaters
 Contain chlorophyl (manufacture their own
food) but also obtain some food from bodies
of their victims
Insect Eaters
 Venus fly trap
 Leaves are hinged
so they can close like
jaws of a steel trap
 Tiny hairs on the
inside trigger the
jaws when touched
by an insect
Insect Eaters
 Bladderwort
 Underwater plant
 Hollow, bladder-like
leaves filled with water
 When trigger hairs are
bumped the leaf
expands and creature is
trapped as water is
sucked into the leaf
Insect Eaters
 Pitcher plant
 Attracts insect with
its bright color leaves
and smell of its
honey like nectar
 When an insect
lands on the rim it
slides down the
slippery sides and
becomes trapped
Insect Eaters
 Sundew
 Attracts insects with
its glistening bait –
sticky “dew drops”
 Insects get stuck on
the dew drops and
then the long hairs
close around it.
Roots and Stems
 Shoot System –
every part of the
plant visible above
ground
 Root system –
part of the plant
located below the
ground
Roots
Roots:
 Always grow downward
 Anchor plant in soil; keep soil from
washing or blowing away
 Main job is to absorb water and minerals
for the plant’s use
 Taproot – main root that goes deep into
the ground to locate water
How a root functions
 A root grows only at its tip. The root cap
is a layer of protective cells that cover the
tip. Root hairs, tiny projections near the
end of the root, worm their way through
the soil to find water. Roots absorb more
water than is necessary. Water that is
not needed evaporates through the
stomata.
 Roots are the shipping and receiving
warehouse for the plant (bring in water
and minerals to the leaves; store extra
glucose, food)
 Roots store extra sugar by converting it
into substances called starches
Stems
Plant Super highway with 2 pipelines
 1. carries water and minerals from roots
to leaves
 2. carries dissolved food from leaves to
stem to roots
Parts of stems
 Stem tip – upper part – produces plant’s
growth
 Cellulose – tough material made by plant cells,
forms a strong cell wall around each plant cell
 Cell Wall – outer membrane of plant cell
 Stolon (runner) – stem that grows along the
surface of the ground
 Rhizomes – thick storage stems below the
ground that help produce new plants
Tropism
Def: growth of a plant in response to a
condition in its environment
4 types of Tropism
 Geotropism – plant’s response to gravity
 Hydrotropism – plant’s response to water
 Phototropism – plants response to light
 Thigmotropism – plants response to
touch