Germination U 14 Lesson 6

Foliage leaves

Cotyledon

Cotyledon

Hypocotyl

Hypocotyl

Radicle

Seed coat

Hypocotyl

Cotyledon

Epicotyl

Common garden bean

Objectives

You should be able to:1. describe the parts of a dicotyledonous (dicot) seed.2. state the function of each part.3. describe the changes that occur during germination of dicot seeds.

The parts of a ‘dicot’ seedhttp://www.saburchill.com/chapters/chap0047.html

Haricot bean: front view and opened with one cotyledon removed

Structure-function relationships

Fill in the functions CHECK

Name of Structure Function of Structure 

Testa protect the embryo and cotyledonsCotyledons store of foodEmbryo young plantPlumule undeveloped shootRadicle young root Micropyle hole for passage of water into seed and through which radicle grows Hilum scar marking point of seed attachment to placenta of fruit

Endosperm store of food in some seeds                   

Visit these websites

• http://www.biology-resources.com/documents/plants-seeds-2.doc

• http://www.biology-resources.com/documents/plants-seeds-4.doc

• http://www.biology-resources.com/biology-videos-plants.html

Germination

Use what you know about germination of dicot seeds to describe the changes seen in this seed as it germinates.

Conditions needed for germinationThree tubes were set up as shown.

After one week:

Tube A: The seeds started to germinate

and then stopped

Tube B: The seeds germinated

Tube C: The seeds did not germinate

  http://www.saburchill.com/questions/c47q02.html Answer the questions on the next slide.

Conditions needed for germination cont’d

1. Explain why the seeds in test tube A started to germinate and then stopped.

2. Why did the seeds in tube C not germinate at all?

3. What conclusion do you draw from this experiment?

CHECK

Answers1. The soaked seeds would have imbibe water and

started to become physiologically active. But, with no further water, all activities would cease.

2. The soaked seeds would have imbibed water and started to become active. But the tube had so much water that the seeds would soon become water-logged and soon rot and die. Also, they could not take in any oxygen to begin respiration.

3. Seeds need to absorb water to start the activities associated with germination. To continue growing, seeds need water but an excess will cause them to die.

Conditions needed for germination cont’d

In your notebook, complete a table like this to show the importance of each factor involved in germination. CHECK

Factor ImportanceMoisture/water (To activate enzymes and enable

hydrolysis of stored foods so respiration can occur)

Suitable temperature (Enzymes need a certain optimum emperature at which to become active)

Oxygen (Oxygen is needed for respiration in the cells that are actively growing during germination)

The Life Cycle of a Flowering PlantC:\Documents and Settings\Administrator\Desktop\Flowers.ppt

Haploid (n)Diploid (2n)

Key

Simplified angiosperm life cycle

Germinatingseed

Seed

Seed

Simple fruit

Embryo (2n)(sporophyte)

Zygote (2n)

FERTILIZATION

Egg (n)

Sperm (n)

Embryo sac (n) (femalegametophyte)

OvuleOvary

Germinated pollen grain(n) (male gametophyte)

Pollentube

Anther

Maturesporophyteplant (2n)