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SCIENCE NOTES
BOTANY

Science Notes

Plants
History
Earth is 4
...
The first organisms evolved 3 billions year ago
who made their own food using sunlight and gave off oxygen
...
Animals eat ready-made food while plants make food
Plant Classification

CLASSIFICATION OF LIVING THINGS
The Five Kingdoms

PLANTS
(have true roots and
stems
...
g
...
Include algae
(no true roots/stems)

PROKARYOTES
(Bacteria)

FUNGI
(do not
photosynthesise, no
true roots/stems)
Yeast,
mushrooms,
truffles

Seaweeds,
spirogyra “Green
Slime”

FLOWERS
YES

NO
YES

LEAVES – long parallel veins,
seed in one part

MONOCOTYLEDONS
e
...
lilies, rushes, flax

LEAVES – single midrib,
network of veins, and seed in
two parts

LEAVES – usually hard,
pointed

CONES

SPORES ON/UNDER
FRONDS damp, shady places
YES

FERNS
DICOTYLEDONS
e
...
beans, dasies,
dandelions

NO

GYMNOSPERMS
e
...
pine, totara,
rimu, kauri

NO

MOSSES AND
LIVERWORTS
(grow on flat
ground)

Science Notes

Photosynthesis

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


plants are the only organisms which can photosynthesise
photo = light, synthesis = joining together
raw materials needed are carbon dioxide from air (taken through leaves) and
water (taken through roots)
the two combine and produce sugar and oxygen
sunlight is the energy source needed for this chemical reaction
the green pigment is chlorophyll which is needed to use light properly
chlorophyll is contained in chloroplasts inside leaf cells

Testing For Carbon Dioxide
If bromothymol blue indicator is added to Elodea (oxygen weed) and put in sunlight, it
turns from blue to yellow because the plant takes in CO2 from the indicator and gives
out O2 so it turns back to blue
...
A gas will be
collected in a test tube and presense of oxygen will be tested using a glowing splint
...
Wash leaf
in water to soften
...

Chemical equation for photosynthesis:
6CO2 + 6H2O

Sunlight and chlorophyll

C6H12O6 + 6O2

Chemical equation for glucose to starch:
n(C6H12O6)  (C6H12O6)n

Summary of Photosynthesis
Uses light energy from the Sun
...
Process also involves carbon dioxide from the air and water from
soil
...
Glucose is made,
which is later converted to starch
...


Science Notes

The Leaf



plants turn their leaves towards the Sun so they have enough sunlight
plants spread their leaves out so they do not overlap each other

Parts of a Leaf:
Midrib: Supports the leaf
...

Cuticle: A waxy layer which protects leaf from losing too much water
...

Epidermis: Packed cells at top and bottom of the leaf which give it support
...
Close to upper surface of
leaf so they receive maximum sunlight
...
They are spread around the cell wall to
receive carbon dioxide
...
Water on cell surface evaporates into air spaces with the leaf
and out through openings in epidermis
...
It is unavoidable that some water will diffuse out as the
carbon dioxide enters, to control this loss the guard cells close at times
...

Xylem: In the veins
...

Phloem: In the veins
...

Veins: Contain the xylem and phloem
...

Petiole: Attaches leaf to the stem
...
Takes away food
from leaves made during photosynthesis to other parts of the plant
...

Palisade cell in depth:

Science Notes

Transpiration
Transpiration: Loss of water in plants
...
Since transpiration
occurs when water evaporates from the stomata, any condition which
affects evaporation will affect the rate of transpiration:
1
...
Stomata is on the underside of the leaf, shielded from
heat
...
Wind: Transpiration is rapid in wind
...

3
...
On a humid day
there is not much room for moisture so transpiration is slow
...
Light: Light affects guard cells and causes them to open or close the
stomat
...

5
...

A potometer is used to measure the rate at which leaves lose water
...
So the faster
the drops move, the faster plant losses water from transpiration
...

Inside the root hair cells, there are many large particles of cell chemicals
dissolved in water, mnaking the water concentration low
...

Water concentration in the soil is high because few particles are dissolved
...

Water moves by osmosis through our blood vessels and body tissues
...

Xylem cells help support the plant because they are arranged around the
outside of the stem, it acts like reinforcing
...
Cells full of these
materials pack the stem tight and help with support
...
The xylem gets rushed into the middle to form rings
...
One
light and one dark ring represents one year’s growth, so you can work out a
tree’s age by counting rings
...

Sapwood: Living, outermost portion of a woody stem which is light in
colour

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