Teaching aims:

1.        概述花的主要结构。

2.        描述传粉和受精的过程，阐明花与果实和种子的关系

3.        认同花、果实、种子对于被子植物传种接代的重要意义，养成爱护花的习惯。

a.        Identify the flower structures and function.

b.        Introduce the processes of pollination and fertilization.

c.         Understanding the relationship between flowers and fruits with seeds.

d.        Realise the importance of protecting the flowers.

e.         Develop an attitude of respect for life.

Teaching focus &difficulties:
1.雄蕊和雌蕊（花蕊）与果实和种子形成的关系。
2.受精的过程及受精后子房的发育。
3.让爱花的习惯成为学生的一种自觉行动。

a.       Understanding the relationship among the stamens, the pistil, the fruits and the seeds.

b.       Understanding the process of fertilization and the development of the ovary.

c.         Develop an attitude of respect for life.

Aids:

Multimedia, flower model, pictures, flowers & apparatus.

Words to know:

germination  [7dVE:mi5neiFEn]  when a seed begins to develop after a period of dormancy, it is called germination.

angiosperm: [5AndVIEusp\:m ]:被子植物

A plant whose ovules are enclosed in an ovary; a flowering plant.

          一种胚珠被包在子房里的植物；一种开花植物

sepal [5sepEl, 5si:pl] 萼片

One of the separate, usually green parts forming the calyx of a flower.

形成花萼的一片独立的、常为绿色的部分

calyx [ 5keiliks ] [植]花萼,The sepals of a flower considered as a group.n.

receptacle[ri5septEkl] 【植】花托 The expanded tip of a flower stalk or axis that bears the floral organs or the group of flowers in a head.

ovule [5Euvju:l ]: 胚珠

A minute structure in seed plants, containing the embryo sac and surrounded by the nucellus, that develops into a seed after fertilization.

种子植物的一个小的结构，含有胚囊并被珠心所包围，施肥后长成种子

ovary [5EJvErI ]:子房 ovary protects and feeds the seed in a plant

The ovule-bearing lower part of a pistil that ripens into a fruit.

          雌蕊中含有胚珠的较底的部分，成熟为果实

pistil [5pIstIl] : 雌蕊，the female part of the plant

The female, ovule-bearing organ of a flower, including the stigma, style, and ovary.

雌蕊群包括柱头、花柱和子房的花雌蕊，长有胚珠

stigma [5stI^mE ]柱头

The receptive apex of the pistil of a flower, on which pollen is deposited at pollination.

雌蕊花柱顶部，授粉时花粉被旋转于此

style  花柱

The usually slender part of a pistil, situated between the ovary and the stigma 柱头

位于子房及柱头之间的，雌蕊之通常较细的部分

stamens [steimen]  雄蕊 the male parts of the plant

pollen  [5pRlEn] n花粉powdery dust on ends of stamens

pollination [ pCli5neiFEn ]n.授粉the way pollen gets from stamens to pistil

anther  [5AnWE]n.【植】花药, 花粉囊

pollen grains 花粉粒

longitudinal section [ lRNdVItju:dIn(E)l] 纵切面

germination of the pollen tube [7dVE:mi5neiFEn] 

sperms 精子

embryo 胚

integument [In5te^jJmEnt] The envelope of an ovule.

 珠被胚珠的外皮

embryo sac 胚囊

micropyle   珠孔

polar nuclei  极核

pollinate  对…授粉

fuse     融合

double fertilization 双受精

endosperm 胚乳

a fertilized egg 受精卵

fertilization 受精 The process that the sperm and the egg fuse as a fertilized egg is called fertilization.

cotyledons 子叶: The cotyledon is the part of the seed that stores food for the young plant.

dicotyledons 双子叶植物

monocotyledons 单子叶植物

fruit coat  果皮

dicot. The plant with two cotyledons are called a dicot. The plant with one cotyledon is a monocot.

Teaching Procedure:

Step one Presentation

Recently, we’ve investigated some flowering plants. Do you remember why we said that leaves, roots and seeds are important?

 (Leaves help the plant make food for itself.

Roots and root hairs help to bring water and minerals to feed the plant.

Every seed contains the embryo plant and seeds also provide the embryo with a source of food during early growth. Every green plant in the world starts from a kind of seed.

Roots, stems and leaves belong to the vegetative organs. Seeds belong to the reproductive organs.)

So far, we have only been considering half the story. Where are the seeds from? How do the fruits and seeds form? Do you know? Now please watch the video carefully. May be you can get some hints form it. And then, please tell me what interesting things are happening?

Video→ Flowers are blooming. Flowers are in blossom.

Does it have any special meaning to a plant? What do you know about the flowers? When you think about flowers, what comes into your mind at first?

Let’s have a brainstorm.

Flowers

         Bees                                     seeds

       beautiful                                  fruits

  smell good

spring                                         baby

etc.

Most people think that flowers are beautiful. But flowers do more than give us beauty. All parts help to keep the plants alive. Each part of a plant does some of the work. As part of a plant, they also do an important job. In your opinion, what is a flower’s job? Flowers are beautiful. But if you pick them up, you will stop a very important procedure. Do you know what it is?

The flower’s job is to help the plant produce more plants. How does it happen? Do you know? You know something about the flowers. But do you know exactly how they do it. In order to answer this question, we must identify the different parts of a flower and understand the function of each part at first.

Step two Flower Structures

Now I’ll give each pair of you a flower. You can dissect them. When you dissect the flower, please compare your flower with the picture on the screen. You’ve noticed that the flower on the screen is different with yours. But their structures are similar. Because we can’t find peach blossom at this weather, you can use these flowers instead. Dissect carefully, and try to identify the flower parts one by one. Remember the name of each part. Keep thinking, “What functions are these structures? What are the main structures of a flower?” After your exploring, please propose a hypothesis.

Ready? What’s your hypothesis?

Does anyone think this part (petals, stamens, pistils, sepals and receptacle) is the most important structure of a flower? Why? Tell me the reason.

Do you know the function of this part?

What will happen to them in the future?

Now bring up your hypothesis and let’s study a flower part by part. Look at this peach flower. These are the beautiful petals. Inside the petals, those flat lollipop-shaped objects are called stamens. If you squeeze the tip, you’ll see the yellow powder. That’s called pollen. Look, this sticky, vase-shaped part of the flower called the pistil. The bottom part of the pistil is fat. This is called the ovary. In the ovary, there is an ovule.

Now can you remember all the structures? Let’s check.

Step three Pollination

At the beginning I have said the job of flowers is to help reproduce plants. Then which special parts of flowers will do the work of reproduction?

 In chapter one, we’ve learned female sex cell & the male sex cells. Do you still remember what they are? (eggs & sperms) During the process of sexual reproduction, what will happen between sperm and egg? (They must fuse.) After one sperm fuses with an egg, we call it what?( a fertilized egg) The process that the sperm and the egg fuse as a fertilized egg is called fertilization. Can mosses’ sperms fuse with egg without water? So what environment do mosses live in? Flowering plant reproduction is similar to the mosses’, but there is a big difference. How it goes in the flowering plant reproduction? Now let’s begin our investigation.

The pistil is the female part of a plant. Female sex cell is in the ovary. The stamens are the male parts. There is a yellow, powdery substance on the top of stamens. This powder is called pollen. The pollen contains the male sex cells.

To reproduce, the pollen must be carried away from the stamens, the male part of the plant. And it must be placed on the pistil, the female part of the plant. The way pollen gets from stamens to pistil is called pollination.

How does pollen travel? Now let’s watch the video. Please pay attention to what can help the flower to finish the pollination.

Bees, butterflies, and birds carry pollen from flower to flower. Like this, Video

When an insect visits a flower, some of the pollen sticks to its body and legs. This pollen drops off as the insect goes to another flower. Sometimes wind also blows pollen from the stamens to the pistil. Like this. Video

So at the stage of the pollination, what weather do farmers hate most?

Why? Because rain will interfere the process of pollination, especially to the pollination depends on the wind. Pollen can’t be carried to the pistil from stamens successfully. If this happen, human being can supply the help.

Video.

Step four  Fertilization

Pollen grains are produced in anthers of the stamens. If the pollen falls on the pistil, it germinates and grows down the pistil. Look, like this. Video In the extension beyond the pollen tube, there are two sperms.

1.      Longitudinal section through an ovary (ovule);

2.      Germination of the pollen tube (sperms)

The egg is located in the ovule. In the outside of an ovule is the integument, within which is the embryo sac. In a mature embryo sac, the two nuclei in the center are polar nuclei, the large cell next to the micropyle is the egg.

   When flowers are in blossom, pollen grains are pollinated to the stigma. Soon afterwards pollinated grains grow beyond the pollen tube. The two sperms inside reach the embryo sac through the pollen tube. One sperm fuses with the egg resulting in a fertilized egg; the other sperm combine with the other two polar nuclei to form fertilized polar nucleus. This event is called double fertilization. The fertilized egg will develop into an embryo and the fertilized polar nucleus will develop into endosperm in future. Embryo is the beginning of a seedling.

During the process of sexual reproduction, the sperm and egg cell must be fused. The process that the sperm and the egg fuse as a fertilized egg is called fertilization.

 Have you noticed the difference between mosses with the flowering plants reproduction?

(Flowering plants can finish fertilization without water.)

That’s why flowering plants can grow taller and they’re more developed than the mosses.

Step five Formation of fruits and seeds

Once the male and female sex cells join, a seed forms in the ovary. Video

After double fertilization, floral and stamens will wither. The stigma and style become fade at the same time. After a while, the flower falls away. But the ovary continues to grow and develop. Over time, the ovary grows even fatter. It becomes a fruit. The fruit protects and feeds the seed. The fertilized egg inside the ovule of the ovary develops gradually into an embryo, the fertilized pole nuclei develop to become the endosperm. Video When the embryo and endosperm develops, the integument develops into a seed. Meanwhile, the ovary wall develops into fruit coat. The whole ovary turns into a fruit.

1.        Longitudinal section through an embryo

2.        Longitudinal section through a seed

Up to now, we can see whose hypothesis is right.

   After the fruit and seeds are mature, they drop from their parent. If the environment permits, they will germinate and grow into new seedlings.

After a period of time, the seedlings will develop into plants that have vegetative organs such as roots, stems and leaves. When the plants grow and develop to a certain stage, they begin to form flower buds, and then they will blossom and produce fruits. The formation of flower buds marks the beginning of reproductive growth.

Now have you realize that when you pick up a flower, you stop what important process?

Life goes in circles.

Step five Discussion

1. Will all the plants develop into fruits?

Look at these cucumber flowers. Some flowers can develop into the fruits & seeds, but others can’t. Why?

(Some plants, such as the cucumbers, have male and female flowers. The male flowers will not develop into fruits.)

2. Before blossom, take the pistil out of peach blossom A, take the stamens out of peach blossom B, and wrap them together with peach blossom C in one plastic bag. Finally, which peach blossom will develop into a peach? Why?

(Peach blossom B & Peach blossom C can develop into the fruits. Because blossom A has no pistil.)

3. Is a watermelon a fruit or a seed? How can one watermelon contains so many seeds?

(There are a lot of ovules in the watermelon’s ovary.)

Step six Exercises:

1. Fill in the blank with the words below:

1.      When pollen lands on a pistil, ______________ takes place.

2.      The tops of ___________ are sticky.

3.      Wind can blow _________ from the stamens to the pistil.

4.      Bees can carry pollen from the __________ to the pistil.

2. Choose the correct answer.

1.      ___________are the main structures of a flower:

a) petal & calyx   b) nectary & receptacle   c) pistil & stamens

2.      The fruit ________ the seed.

a) protects and feeds   b) pollinates   c) eats

3.      Seeds are carried to different places by _________.

a) wind        b) animals     c) wind and animals

4.  The pollen tubes:

a)      Store sperms;

b)      Make sperms arrive at a embryo sac

c)      Supply nutrition for sperms

5. Double fertilization in angiosperm refers to:

a)                Two sperms fuse with two egg cells.

b)                Two sperms fuse with one egg cell

c)                Two sperms fuse with one egg cell and two polar nuclei respectively.

3. Read &Match

Petal                  embryo

Stamens               fruits

Style                  fruit coat

Ovary                 seed

Ovary wall              wither

Ovule

A fertilized egg         

Now we’ve learnt the whole process from a flower turning into a fruit and seeds.