Chapter 6: Sexual Reproduction in Flowering Plants

Question 1

What are the parts does a flower consists of?

Answer 1

• pedicel
• sepal
• petals
• carpel
• stamen

Question 2

What do carpel and stamen consist of?

Answer 2

Carpel
- stigma
- style
- ovary
Stamen
- anther
- filament

Question 3

What are anther and filament?

Answer 3

Anther
- consist of four pollen sacs
- produces pollen grains
Filament
- holds the anther

Question 4

What are style, stigma, and ovary?

Answer 4

Style
- supports the stigma
Stigma
- receives pollen grain
Ovary
- contains one or more ovules

Question 5

Explain the formation of pollen grains in an anther.

Answer 5

• anther consists of four pollen sacs which contain microspore mother cells
• each microspore mother cells undergo meiosis to produce four haploid microspore cells
• the haploid nucleus divides by two through mitosis
  to form two nuclei called tube nucleus and generative nucleus
• a thick sculpture is formed around them which develops into pollen grains

Question 6

Explain the formation of the embryo sac in the ovule till a haploid number of cells are formed

Answer 6

• ovule is made up of nucellus
• nucellus forms 2 layers of integument
• at the end of both layers there is an opening called micropyle
• one of the nucelli forms megaspore mother cell
• also known as embryo sac mother cell, it undergoes meiosis to form 4 haploid megaspore cells
• three cells degenerate while one of it develops into an embryo sac

Question 7

Explain the formation of the embryo sac in the ovule from the haploid cell till the end.

Answer 7

• nucleus of the embryo sac divides 3 times through mitosis to form 8 nuclei
• one nucleus from each group of 4 moves to the center to form polar nuclei
• three nuclei form antipodal cells
• two synergid cells and one egg cell is produced at another end
• this is a mature ovule

Question 8

What is pollination?

Answer 8

• transfer of pollen grains from the anther to the stigma of the flower

Question 9

Pollination occurs with the help of ______ ______ such as ___, water, ____, mammals, and birds.

Answer 9

• pollinating agents
• wind
• insects

Question 10

State two types of pollination and explain them.

Answer 10

• self pollination-transfer of pollen from the anther of a flower to the stigma of the same flower or different flower on the same plant
• cross pollination-transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant but of the same species

Question 11

Explain the germination of pollen grains.

Answer 11

• pollen grains are transferred during pollination
• secretion of a sugary solution on stigma stimulates the pollen grains to germinate
• a pollen tube grows out towards the ovule through style

Question 12

Explain the formation of male gametes.

Answer 12

• tube nucleus moves to the tip of the pollen tube
• tube nucleus controls the growth of the pollen tube
• along the way, the haploid generative nucleus divides by mitosis to form 2 haploid male nuclei
• pollen tube penetrates the ovule into the micropyle as it reaches the ovary
• the tube nucleus disintegrates and the tip of the pollen tube bursts
• 2 male nuclei move into the embryo sac

Question 13

Explain the double fertilisation in the formation of diploid zygote and triploid nucleus.

Answer 13

• double fertilisation occurs when 2 male nuclei enter the embryo sac
• one of the male nuclei fuses with the egg cell to form a diploid zygote
• other male nucleus fuse with 2 polar nuclei to form a triploid endosperm nucleus
• fertilisation occurs twice as there are two male nuclei
• diploid zygote develops to form an embryo
• the embryo consists of plumule, radicle, and cotyledon
• the triploid endosperm nucleus develops to form endosperm

Question 14

What is the importance of double fertilization for the survival of flowering plants?

Answer 14

• Formation of embryo and endosperm
• Production of a large variety of plants
• Formation of fruit and seeds

Question 15

Explain the embryo development.

Answer 15

• diploid zygote divides mitotically to form basal cell and terminal cell
• basal cell develops into a suspensor which anchors the embryo to the wall of the embryo sac
• the terminal cell develops to become an embryo
• ovule develops into a seed and 2 layers of integument develop to form testa to protect the embryo

Question 16

Explain the development of fruits.

Answer 16

• ovary develops into a fruit
• ovary wall becomes the fruit wall ( pericarp )
• stigma and style at one end wither while at the other end, the pedicel becomes the fruit stalk
• petals and sepals fall off

Question 17

What are the 4 types of fruits?

Answer 17

• simple fruit
• aggregate fruit
• multiple fruit
• accessory fruit

Question 18

Explain simple fruit and aggregate fruit.

Answer 18

Simple fruit
- a fruit that develops from a single carpel on a single flower
- fruit may be fleshy or dry
- mango, pea, orange, and tomato develop from a single ovary with one or more ovules
Aggregate fruit
- develops from a single flower with numerous separate carpels ( several ovaries )
- produces many tiny fruits clustered tightly together
- raspberry and strawberry

Question 19

Explain multiple fruit and accessory fruit.

Answer 19

Multiple fruit
- formed from carpels of a cluster of flowers ( inflorescence )
- pineapple, jackfruit, and fig
Accessory fruit
- fruit develops from a tissue that is not in the ovary but from some tissues near the carpel
- apple and pear

Question 20

What is the importance of seeds for the survival of plants?

Answer 20

• a seed contains an embryo that germinates to form seedlings
• endosperm or cotyledon is the source of nutrients for germination
• seeds enclosed by testa are impermeable to prevent seeds from spoling