Reproduction in Plants

Question 1

Chromosomes

Answer 1

Long threads of DNA found in the nucleus, they contain sets of instruction known as genes.

Question 2

Asexual Reproduction

Answer 2

A process resulting in the production of genetically identical offspring from one parent through the division of chromosomes, which make similar cells.

Question 3

Stem tuber

Answer 3

A swollen part of a stem, which stores food

Question 4

Zygote

Answer 4

The diploid cell produced when two garmetes fuse together

Question 5

Gametes

Answer 5

Gametes only contain half as much as chromosomes than usual cells in order to make sure that the zygote they form when fused together will have the correct number of chromosomes

Question 6

Diploid cell

Answer 6

The cell in which a full number of chromosomes are present, two complete sets is called a diploid

Question 7

Haploid

Answer 7

A cell in which only half the number of chromosomes are present.

Question 8

Meiosis

Answer 8

Reduction division in which the chromosome number is halved from diploid to haploid

Question 9

Sexual reproduction

Answer 9

A process involving the fusion of the nuclei of two gametes to form a zygote and the production of the offspring that are genetically different from each other.

Question 10

Fertalisations

Answer 10

The fusion of gamete nuclei

Question 11

Egg

Answer 11

The large reproductive cell which does not move much.

Question 12

Important point

Answer 12

Inside the petals are the stamens. These are the male parts of the flower. Each stamen is made up of a long filament, with an anther at the top. The anthers contain pollen grains, which contain the male gametes. The female part of the flower is in the centre. It consists of one or more carpels. A carpel contains an ovary. Inside the ovary are many ovules, which contain the female gametes. At the top of the ovary is the style, with a stigma at the tip. The function of the stigma is to catch pollen grains.

Question 13

Pollen grains

Answer 13

Tough, resistant structures containing the male gametes of a flower, made at the anthers.

Question 14

Ovules

Answer 14

A structure in the ovary of a flower which contains a female gamete

Question 15

Anther

Answer 15

The anther has four spaces or pollen sacs inside it. Some of the cells around the edge of the pollen sac s divide by meiosis to make pollen grains. When the flower buds open the anther splits up to expose a yellowish powder which is pollen.

Question 16

Pollination

Answer 16

The transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma)

Question 17

Self pollination

Answer 17

When pollen is carried to the stigma of the same flower or to another flower of the same plant is known as self pollination

Question 18

Cross pollination

Answer 18

The transfer of pollen grains from the anther of a flower to the stigma of a flower in a different plant of the same species.

Question 19

Insect Pollinated flowers

Answer 19

• Large with conspicuous petals, often with guide lines
• Often strongly scented
• Often have nectaries at the base of petals
• Anthers and stigma are present in a way in which insects have to brush past them to reach nectar
• Sticky or spiky pollen grains
• Large quantities of pollen made, because some will be eaten and some will be delivered to the wrong plants

Question 20

Wind pollinated

Answer 20

• Small inconspicuous petals, or no petals at all
• No scents
• No nectaries
• Anthers dangle outside the flower to catch wind
• Stigma large a feathery and dangling outside the flower to catch pollen grains carried by the wind
• Smooth and light pollen
• Very large quantities of pollen made as some will be blown away

Question 21

Fertilisation

Answer 21

After pollination the male gametes needs to reach the female gamete which is inside the ovule which again is inside the ovary. So the male gamete if landed on the right stigma begins to grow a tube into the wall of the ovary by secreting enzymes to create a pathway. Then at the end there is a small hole in the cells which surround the ovule, integuments, called micropyle, in which the pollen enters the female gamete to begin fertilisation.

Question 22

Seeds

Answer 22

Once the ovule is fertilised, many parts of the flower such as the sepals, petals and stamens have done their job, so they wither and fall off. Inside the ovary each ovule will contain a zygote which divides by mitosis to form an embryo plant. This ovule is now called as the seed, the integuments of the ovule becomes hard and dry to form the testa of the seed. the seed will become dorment.

Question 23

About the Seedn

Answer 23

The embryo consists of a radicle which will grow into a root and a plumule which will grow into a shoot. Food for the embryo is stored inside two creamy colored cotyledons which is surrounded by a hard coating called testa. These contain starch and protein along with enzymes. The testa stops damage to the embryo either by bacteria or fungi. The testa also has a tiny hole in it called the microphyle. When a seed is separated from the plant there is a scar near the micropyle called the hilum where the seed was joined to the pod.

Question 24

Seed Germination

Answer 24

A seed contains no water, when its formed on the plant all water is drawn out to make it dehydrated. This means the seed is dormant as no metabolic reactions can occur without water. This is important so that the seed can survive harsh conditions such as extreme cold or drought where a living plant would be killed.

Question 25

Seed germination start

Answer 25

When a seed germinates, it first takes up water through the micropyle which sends water to the cotyledons making them swell, this will make the testa burst. Once there is sufficient water the enzymes in the cotyledons become active, amylase break starch into maltose and protese break proteins to amino acids, which are dissolved in the water to reach the embryo to help it grow.