Topic 2The World of Plants

Standard Grade Biology

World of Plants is divided into:

A- Introducing plants

B- Growing plants

(Pollination, Fertilisation,

Asexual reproduction)C- Making food

The life cycle of a plant

• There are 7 stages in the life cycle of a plant. seed /

fruit Formatio

n

seed dispersal

germinationflower

formation

pollination

fertilisation

development

Seed Structure

• Parts are:Seed coatForms a tough protective layer

Food storeProvides the embryo plant with food.

Embryo shoot

Embryo root

Embryo – grows into plant

Seed Dissection

• Using a scalpel, carefully dissect your seed in half lengthways.

• Draw a diagram of what you can see.• Identify the parts,and label your drawing(workbook p13).

Seeds

Investigation: Germination

• This is an Exam Board Investigation that makes up part of your Practical Abilities grade (20% of finals)

• Planning may be done in small groups but after this you must work on your own

• Write in your Investigation booklet.

What affects germination?

3Bio2 Brainstorm 16/03/07• Spacing / number of seeds• Humidity / water volume• Type of seeds• Size of seeds• Type of soil / mass• Temperature• Depth of planting• Gases / oxygen levels

Measure by % germination after set time

Germination and Temperature

• Example of results table. Also draw a graph.

• What conclusions can you draw from your experiment?

• How could you have improved it?

TemperatureoC

No. of seeds

No. of seeds

germinated

Percentage germinatio

n

4 25

20 25

50 25

Germination conditions

• Seeds need certain conditions to germinate:– Water

• to activate enzymes which digest stored food

– Oxygen• Needed for the production of energy for

germination

– Warmth• Needed for the enzymes to work effectively.

• Germination is the development of a new plant from the embryo in a seed.

Germination and Temperature

• The best temperature for germination of a species of plant is known as the optimum temperature.

• The optimum temperature is normally between 15oC and 30oC.

Structure of a Flower

Petal

Stigma

Anther

Petals

Stigma

AntherFilament

Ovary

Sepals

Ovules Nectarie

s

Style

Collect a cut-out flower, colour it in and put it together.

Carpelfemal

e parts Stamen

male parts

What do the parts do?

Sepals- protect the flower when it is a bud

Petals- colourful to attract the insects

Nectaries- give out sugary liquid to attract insects

Stamen- anther produces male sex cells (pollen)

Carpel- stigma traps pollen

Style is where pollen tube grows down to female sex cells.

Carpel- ovary produces female sex cells (ovules)

Quick Test1. Why is the seed coat important?2. Name the parts of the embryo plant.3. Why is the food store in a seed important?4. Name the three factors required for

germination.5. Where are a plant’s sex organs found?6. Name two parts of a flower that attract

insects.7. Name the male part of a flower.8. Which part of the flower contains ovules?9. Which part of the flower produces pollen?10.Which part of a flower catches pollen

grains?

Pollination

• Pollination involves the transfer of pollen (male gamete) from the anther to the stigma (outermost female part)

• If it is in the same flower it is calledself-pollination.

• If between different flowers it is calledcross-pollination

• Plants are pollinated by insects or the

wind.

Insect Pollinated Plants

Wind Pollinated Plants

Pollination Activity

• Look at the Botanics Posters• Which features are from wind

pollinated or insect pollinated plants?

• Workbook p28– Construct a table to show

the differences between insect and wind pollinated plants.

Pollination Summary

Structure Wind Pollinated

Insect Pollinated

Petals

Pollen

Stamen

Stigma

nectar

dull

light

dangling

feathery

none

bright colour

sticky

inside flower

sticky

makes sugar

Hayfever

World of plants workbookG – pages 34 &35C- pages 36 & 37

• Answer Q 1 – 5 on hayfeverand• Answer Q 1 – 5 on pollenin the air from Feb - Sept

Fertilisation

• Fertilisation involves the fusion of the nucleus of the male gamete (in the pollen) with the nucleus of the female gamete (in the ovules).

Fertilisation

Pollen tubes

• The pollen grain grows a tube.• The tube reaches an ovule.• The gamete nuclei fuse (fertilisation) and

a zygote (seed) forms.

Pollen tube growth

Fertilisation

Once fertilisation has taken place the zygote (fertilised ovule)becomes a seed, and the ovary becomes a fruit.The petals die and fall off.The plant seeds are in the fruit.

What are fruits like?

The fruits can be:

- soft & fleshy

- hard & dry

• What fruits can you think of?

• What are their seeds like?

• Draw a table with headings for each type and write some examples for them.

Types of Fruits

Soft & fleshy Hard & dry

AppleTomato

Hazelnut

Seeds must be carried away (dispersed / scattered) from the parent plant to:

• Reduce overcrowding

Seed Dispersal- why?

• Reduce competition for:

- Water

- Light

- Nutrients

Seed Dispersal

Dispersal method

Description Seeds/ Fruits

Wind Seeds are designed to travel as far as possible.May have extensions which act as parachutes or wings.Fruits may be shaken like a pepper pot.

Seed DispersalDispersal method

Description Seeds/ Fruits

Animal (internal)

Fruit is brightly coloured to attract animals.When eaten the seed travels with the animal, survives acidic digestive juices and is passed out in the faeces.

Seed Dispersal

Dispersal method

Description Seeds/ Fruits

Animal (external)

Some have little hooks or sticky substances so they stick onto the animal’s fur, are carried away and rubbed off later.Some carried away by animals and dropped.

Activity

• Cut out the seeds, match and stick them into appropriate columns in a table, for:

Wind Animal (external)Animal (internal)

[There is also mechanical (eg broom, sea cucumber) and water (eg coconut) but you don’t need to know them for Standard grade]

Activity

• Listening exercise on seed dispersal– Listen to the tape, – Use the commentary to help you answer

questions on your handout.

World of Plants Workbook p41

Comparing Lime and Sycamore seeds.

Go through the problem solving activity

Quick Test-A

1. What term is used to describe male and female gametes?

2. What is pollination?3. Name the two types of pollination.4. Describe the differences in the pollen

between insect and wind pollinated plants.5. Explain why the stigmas of wind pollinated

flowers hang outside the flowers.

Quick test-B

1. Why do wind pollinated flowers not produce nectar?

2. How does the male gamete reach the female gamete?

3. What is a fruit?4. Name three ways in which fruits and

seeds are dispersed.5. Why is it important that fruits and seeds

are carried away from the parent plant?

Types of reproduction

Sexual reproductionInvolves 2 parents and sex cells ie. pollen

and ovule join to make a new individual.

Asexual reproductionInvolves 1 parent and no sex cells.Ways they naturally reproduce include:

- Tubers- ( Bulbs )- Runners

Tubers

Tubers are underground food stores which stores food over the winter and provides a new plant with food until it can make its own.

Food made by the new plant is sent to make new tubers. Thereby reproducing itself.

Examples: potato, artichoke, yam, cassava, water chestnut, arrowrootTaro-

Japanese potato

arrowroot = arrow root = Chinese potato (this name also is used for jicama) = goo = seegoo = arrowhead = Chinese arrowhead = tse goo = ci gu = tsu goo

Arrowroot

Notes:   The name arrowroot is more commonly associated with a thickener that's made from the plant.A fresh arrowroot tuber looks like a small onion, only without the layers.It should be peeled, and then it can be boiled or stir-fried.Look for it in Chinese markets during the winter.

Cassava

cassava = casava = manioc = mandioca = tapioca root = yucca = yucca root = yuca root = Brazilian arrowroot   Pronunciation:   kuh-SAH-vuh

Notes:   People in Hispanic countries use cassavas much like Americans use potatoes.  There's both a sweet and a bitter variety of cassava. The sweet one can be eaten raw, but the bitter one requires cooking to destroy the harmful prussic acid it contains. 

Topinambour

Notes:  Water chestnuts are delightfully sweet and crisp- if you buy them fresh. You need to peel off their brown jackets and simmer them for five minutes before stir-frying.Tinned Water chestnuts are easily available but not nearly as good. If you use them, blanch them first in boiling water for thirty seconds. 

Topinambour

Water chestnut

Chinese water chestnut

Bulbs

Bulbs are also underground food stores which work in the same way as tubers.

The difference is that bulbs have thick fleshy ‘leaves’.

Keukenhof gardens near Amsterdam Holland.

Stargazer lily

Examples: snowdrop, crocus, daffodil, iris, lily, hyacinths, amaryllis, onion, garlic.

1. Sept.- Oct. Planting TimeThe tulip bulbs are going to be planted twice as deep as the bulb is high. They have no roots at this stage.

2. November Making RootsThe roots start growing out of the base, establish themselves taking nutrients from the soil. Mother bulbs get ready for winter.

3. Dec. - Jan.Cooling PeriodRest period. In order for bulbs to bloom in the spring they need weeks of at least 5oC. Frost at this time doesn’t harm them.

4. Feb. – March Growing PeriodThe bulbs begin to change as the starch, or carbohydrates in them turns to sugar. As this occurs, the leaves and flower gradually push up-wards out of the bulb.

5. April – May Blooming TimeThe tulips are in bloom-they receive their nourishment from the roots-only the brown skin of the bulb remains as all of the energy has gone to the bloom.

6. May – June RegenerationAfter flowering the blooms are cut and the leaves are left on the plant. The new daughter-bulbs use the food in the leaves to grow.

7. July - Sept. MultiplyingUp to five small bulbs can be expected to grow out of the mother bulb. They form their roots slowly, and develop their blooms and leaves within the bulb, for next year's plant.

Runners

Runners are side shoots which grow out from the parent plant.

Buds form at points along the runner and eventually these buds form roots and grow into new plants.

Examples: spider plant (Anthericum), strawberry (Fragaria x ananassa)

Flame violet

(Episcia reptans)

Collect Information Card

“Asexual Reproduction”

Take short notes from it.

Activity

World of plants workbookRead p20“Advantages of asexual reproduction”Read p32 & 33.

– Copy and complete the table.Summarising advantages & disadvantages

of sexual versus asexual reproduction

Reproduction- advantages

Asexual SexualGenetically identical offspring (clones) which have parent’s strong characteristics (but weak ones also passed on) and are suited to their environment.

Narrow distribution spreading over the area quickly as no vulnerable stages involved.

Genetically different offspring- variation.More chance of survival if conditions change.Wide distributionReduces competition for water/light/nutrients as no dense growth around the parent.Using seeds allows the offspring to travel to new areas.

Clones

A clone is the name given to the genetically identical plants produced from a single parent plant.

They are formed during asexual reproduction only.

Artificial Propagation

People can make use of plants’ ability to reproduce asexually (instead of using seeds) by using methods of artificial propagation such as:

- Cuttings- Graftings

Again this produces genetically identical offspring (clones).

Cuttings

They can be placed in moist

soil or water (and sometimes

dipped in rootingpowder).

Cuttings are small pieces of stem with some leaves attached, the new plant grows from this.

Grafting

A cut stem of one plant (with good flower or fruit growth) (the graft) is taken and firmly attached to the rootstock of another plant (which has a strong, established root system) (the stock).

Examples- roses, fruit trees

Grafting- advantages

Allows you to clone the commercial qualities of a particular fruit variety on another tree. Seed trees have highly variable fruit quality.

They come into production much earlier (2-3 years) than trees grown from seed (5-10 years).

Activity

World of Plants Workbook p42

The effect of rooting powder on cuttings

Collect some graph paper and work through the problem solving activity

Activity

World of plants workbook p33

“Artificial propagation- commercial advantages”

Read page. Collect Information sheetWrite short notes on it.

Commercial aspects

Artificial propagation has allowed us to adapt and improve plants for our own use.

Some of the benefits include:

•Quick production of large numbers of genetically identical plants.

•Specific varieties, desired features or consistent quality can be produced especially in fruit, flowers.

Quick Test-C1. How many parents are involved in asexual

reproduction?

2. Name 3 ways in which plants reproduce asexually.

3. Give 2 examples of plants that reproduce asexually by producing runners.

4. What term is used to describe a population of genetically identical plants?

5. Name 2 common methods of artificial propagation.

6. Give the commercial advantages of artificial propagation.

One

Runners, tubers, bulbs

Spider plant, strawberry

Clones

Cuttings, grafting

Quick method, producing large numbers of plants, of known quality and specific variety

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