Parts of a plant

2. FUNCTIONS OF A FLOWER
• Flowers are the organs of sexual
reproduction in plants

3. PARTS OF A FLOWERS

7. LEAVES

9. Plants are the only photosynthetic organisms to have leaves (and not all plants
have leaves). A leaf may be viewed as a solar collector crammed full of
photosynthetic cells.
The raw materials of photosynthesis, water and carbon dioxide, enter the cells of
the leaf, and the products of photosynthesis, sugar and oxygen, leave the leaf.

10. Cross section of a leaf, showing the anatomical features important to the study
of photosynthesis: stoma, guard cell, mesophyll cells, and vein. Image from
Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates
(www.sinauer.com) and WH Freeman (www.whfreeman.com), used with
permission.
Water enters the root and is transported up to the leaves through specialized
plant cells known as xylem (pronounces zigh-lem). Land plants must guard
against drying out (desiccation) and so have evolved specialized structures
known as stomata to allow gas to enter and leave the leaf. Carbon dioxide
cannot pass through the protective waxy layer covering the leaf (cuticle), but it
can enter the leaf through an opening (the stoma; plural = stomata; Greek for
hole) flanked by two guard cells. Likewise, oxygen produced during
photosynthesis can only pass out of the leaf through the opened stomata.
Unfortunately for the plant, while these gases are moving between the inside
and outside of the leaf, a great deal water is also lost. Cottonwood trees, for
example, will lose 100 gallons of water per hour during hot desert days. Carbon
dioxide enters single-celled and aquatic autotrophs through no specialized
structures.

11. Pea Leaf Stoma

14. outer layer of the
stem
tubes that carry
sap
new parts of the
stem
woody part of the
stem
central part
of the stem
protective covering of
the stem

15. Different types of roots: axis of the plant which grows in the opposite
direction from the stem, maintain the plant in place and absorbs
nutrients.
Fibrous: root formed in bundles where it is not possible to
determine the primary root.
Cauline: roots that shoot from the stem.
Tubercular: root in the form of a tubercle.
Taproot: root that grows vertically into the earth.

17. REPRODUCTIVE ORGANS IN PLANTS
1. Sepals
- protect the unopened to flower
bud
2. petals
- may be brightly coloured to
attract insects
3. stamens
- the male parts of the flower
consisting of the anther held up
on the filament
4. Anthers
- produce male sex cells (pollen
grains)
5. Stigma
- the top of the female part of the
flower which collects pollen
grains
6. Ovary
- produces the female sex cells
(ovules)
7. Nectaries
- produce sugary nectar which

18. Asexual reproduction in plants
Asexual reproduction in plants can take a number of forms:
Vegetative propagation: Many plants develop underground food storage organs
which overwinter and develop into the following year's plant. Examples are bulbs,
tubers (eg potatoes) and rhizomes
Daffodil bulb

19. Plantlets: These can take the form of runners (eg strawberries) or side
branches (busy lizzy).

20. Cuttings: We can make cuttings or grafts, which in the right conditions will
develop roots and grow into a new plant.
Jade plant cutting growing new roots

21. Tissue culture: We can take a few cells from a plant and grow them into a
complete specimen. Tissue culture is a type of cloning; for more on this topic
see the Revision bite on Cloning and genetic engineering)
As only one parent is involved in asexual reproduction, all the offspring have
exactly the same genes as their parent. The offspring are identical and they are
called clones. Because of this, any genetic problems there may be will always
be passed on to the new generation.

22. Sexual reproduction in plants
Many plants reproduce sexually. The advantage to the plant is that its offspring have
a selection of genes from two parents, so each individual's genes are different. The
offspring are not identical, and there is variety in the species.
A flowering plant's sexual organs consist of:
•the stamen, or male sex structure, consisting of a filament and a pollen-bearing
anther at the tip
•the pistil or female sex structure, consisting of ovary and ovule, style, and stigma at
the tip. (The pistil is also sometimes called the carpel.)
Here's how it works:
1.An insect or the wind carries pollen grains from the anther of another flower.
2.The pollen grains land on the stigma and a pollen tube grows down through the
style to the ovary.
3.The nucleus of the pollen grain passes down the tube. It fertilises the egg cell inside
the ovule.
4.The fertilised egg cell develops into an embryo. The ovary becomes the fruit and
the ovule becomes a seed - from which (once dispersed) the offspring plant will grow.

23. FERTILISATION
• When pollen grains land on the stigma of a flower of the correct
species they germinate. A pollen tube grows through the tissues of
the flower until it reaches an ovule inside the ovary. The nucleus of
the pollen grain (the male gamete) then passes along the pollen
tube and joins with the nucleus of the ovule (the female gamete).
This process is called fertilisation.
• After fertilisation the female parts of the flower develop into a fruit.
The ovules become seeds and the ovary wall becomes the rest of
the fruit.

24. POLLINATION

25. DIFFERENCE BETWEEN INSECT AND WIND POLLINATED
INSECT POLLINATED
• large, brightly coloured petals - to
attract insects
• often sweetly scented - to attract
insects
• usually contain nectar - to attract
insects
• moderate quantity of pollen - less
wastage than with wind pollination
• pollen often sticky or spiky - to stick
to insects
• anthers firm and inside flower - to
brush against insects
• stigma inside the flower - so that
the insect brushes against it
• stigma has sticky coating - pollen
sticks to it
WIND POLLINATED
• small petals, often brown or dull green -
no need to attract insects
• no scent - no need to attract insects
• no nectar - no need to attract insects
• pollen produced in great quantities -
because most does not reach another
flower
• pollen very light and smooth - so it can
be blown in the wind
• anthers loosely attached and dangle out -
to release pollen into the wind
• stigma hangs outside the flower - to
catch the drifting pollen
• stigma feathery or net like - to catch the
drifting pollen

26. Seed dispersal
• Seeds are dispersed away from each other and from
the parent plant so that there is less competition. The
commonest methods of seed dispersal are:
1. wind e.g. dandelion, sycamore fruits are light and have
extensions which act as parachutes or wings to catch
the wind
2. animal internal e.g. tomato, plum, raspberry, grape
have brightly coloured and succulent fruits which
contain seeds with indigestible coats which allow the
seeds to pass through the animal undamaged
3. animal external e.g. goose grass, burdock, the fruits
have hooks which attach them to the fur of passing
animals.

27. ASEXUAL REPRODUCTION

28. Advantages for the plant of asexual and sexual
reproduction
• Asexual reproduction
only one parent plant
is required
young plants are
identical to the parent,
so that good features
will always be passed
on
• Sexual reproduction
characteristics are
inherited from two
parents - this
produces variation in
the offspring;
this gives a good
chance of at least a
few surviving
diseases, changes of
climate, etc.

30. Water transport in celery
Aim To observe a movement of water in the
xylem of celery
Equipment
1. Celery stick with leaves,
2. 2 beakers,
3. Razor blade,
4. Dye
Method
1. Arrange the apparatus as shown.
2. 2. Leave it overnight and then observe the
celery stalk closely.
3. Cut the celery stick lengthways and across
the stalk, and note the presence of any
dye.

31. Questions
1. Describe the directions in which the dye travelled.
2. Construct diagrams of the horizontal slice and of the vertical
slice. In each
diagram show where the dye travelled.
3. Explain why one half of the celery stalk was left in water with no
dye.

32. A product of photosynthesis
Aim To investigate the products of photosynthesis
Equipment
1. 2 x 600 mL beakers,
2. 2 glass funnels,
3. 2 test tubes,
4. Sodium hydrogen carbonate solution (0.5 per cent),
5. 2 pieces of actively growing Elodea (Canadian pond weed),
6. light source,
7. wooden splint,
8. safety goggles

33. Method
1. Half-fill each beaker with sodium
hydrogen carbonate solution.
2. Place a piece of plant in each
beaker and cover the plant with a
funnel.
3. Invert a test tube full of water
over the stem of each funnel.
4. Place one beaker in the dark, the
other in continuous light for
several days.

34. Green leaves and photosynthesis
Aim To examine where the products of photosynthesis are
stored in leaves
WARNING: Ethanol is highly flammable. At no stage should the
test tube containing ethanol be placed near any flame.
Equipment
1. Potted plant with variegated leaves,
2. potted plant of the same species with completely green leaves
3. 3 beakers of boiling water
4. 2 large test tubes containing ethanol or methylated spirits,
5. iodine solution,
6. forceps,
7. scissors,
8. 2 watch-glasses or 2 glass Petri dishes,
9. safety goggles

35. Method
1. Cut a leaf from each plant. Cut a small nick in the edge of the variegated
leaf so it can be identified later.
2. Sketch two outlines of the variegated leaf side by side. Do the same for
the green leaf.
3. Drop both leaves into one beaker of boiling water for a few minutes. This
kills the leaf cells so that no further reactions can occur.
4. Using the forceps, remove the leaves and place one in each test tube of
ethanol.
5. Stand both test tubes in the second beaker of boiling water. The ethanol
will start to boil, and green colour will be dissolved from the leaves. After
around 10 minutes the leaves should look quite pale.
6. Using the forceps, remove the leaf from one test tube and dip it into the
third beaker of boiling water for a few seconds. This removes the ethanol
and softens the leaf. Place the leaf on a watch-glass or Petri dish. Repeat
this step for the other leaf.
7. Add iodine solution to each leaf. Allow it to stand for a minute.
8. Dispose of all solutions as instructed by your teacher.
9. On the outlines prepared in step 2, draw and colour in the areas
stained blue-black on each leaf.

37. Extracting chlorophyll from leaves
Aim: To extract chlorophyll from leaves and separate different
types of chlorophyll by paper chromatography.
Materials:
1. Soft leaves
2. 250 ml beaker
3. 50 ml beaker
4. 100 ml measuring cylinder
5. Bunsen burner
6. Heat mat
7. Gauze mat
8. Metal tongs
9. Matches
10. Methylated spirits
11. A test tube
12. Chromatography paper

38. Method:

39. A product of respiration
Aim To investigate the products of respiration
Equipment
1. Flasks and glassware as shown
2. Filter pump,
3. sodium hydroxide solution,
4. limewater,
5. Potted plant, several insects or earthworms
Method
1 Set up the apparatus as shown.
2 Slowly draw air through the apparatus by means of the filter pump.
3 Record any changes in the colour of the limewater in flasks B and D.

41. 1. Sodium hydroxide absorbs carbon dioxide from the air. Carbon
dioxide dissolves in limewater to form a milky solution. Explain
the purpose of flasks A and B.
2. Explain the purpose of flask D.
3. Justify the use of the:
a. plastic bag
b. b black paper.
4. Explain any changes observed in the limewater during the
experiment.
5a.Modify the experiment, using an animal (eg earthworm) in place
of the potted plant in flask C.
b. Compare and contrast the results of the two experiments.

42. Stomata and chloroplasts
Aim To examine stomata and chloroplasts in leaves
Equipment
1. Compound microscope,
2. microscope slides and cover slips,
3. dropper,
4. tweezers,
5. razor blade,
6. stain such as methylene blue or iodine,
7. leaves from various plants such as rhubarb and agapanthus, elodea (a
water plant)

43. Method
Part A—Stomata
1. Set up the microscope.
2. Peel the lower epidermis (outer layer) from the bottom of a leaf. Using
tweezers may help.
3. Place the epidermis flat on the microscope slide.
4. Add a drop of water and carefully lower the cover slip on top. Be careful not to
trap any air bubbles under the slip.
5. Add a drop of stain at one edge of the cover slip and hold a piece of paper
towel at the opposite edge to draw the stain under the cover slip and across
the leaf sample.
6. View the slide under the microscope, identify and draw the stomata.
7. Try looking at the stomata of other plant leaves in the same way.
8. Choose another leaf and try to find stomata on the upper epidermis.

44. Part B—Chloroplasts
1. Take a leaf of elodea.
2. Use a razor blade to cut a very thin slice off the leaf.
3. Place the leaf slice on a microscope slide and add a drop of water and a cover
slip.
4. View the slide under the microscope. Identify and draw the cells containing
green chloroplasts.

45. 1. Outline the purpose of stomata.
2. Stomata are mainly found on the underside of leaves. Explain why.
3. Outline the function of a guard cell.
4. Describe the role of chloroplasts.