Reproduction in Plants Flashcards
Chromosomes
Long threads of DNA found in the nucleus, they contain sets of instruction known as genes.
Asexual Reproduction
A process resulting in the production of genetically identical offspring from one parent through the division of chromosomes, which make similar cells.
Stem tuber
A swollen part of a stem, which stores food
Zygote
The diploid cell produced when two garmetes fuse together
Gametes
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
Diploid cell
The cell in which a full number of chromosomes are present, two complete sets is called a diploid
Haploid
A cell in which only half the number of chromosomes are present.
Meiosis
Reduction division in which the chromosome number is halved from diploid to haploid
Sexual reproduction
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.
Fertalisations
The fusion of gamete nuclei
Egg
The large reproductive cell which does not move much.
Important point
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.
Pollen grains
Tough, resistant structures containing the male gametes of a flower, made at the anthers.
Ovules
A structure in the ovary of a flower which contains a female gamete
Anther
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.
Pollination
The transfer of pollen grains from the male part of the plant (anther of stamen) to the female part of the plant (stigma)
Self pollination
When pollen is carried to the stigma of the same flower or to another flower of the same plant is known as self pollination
Cross pollination
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.
Insect Pollinated flowers
- 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
Wind pollinated
- 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
Fertilisation
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.
Seeds
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.
About the Seedn
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.
Seed Germination
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.
Seed germination start
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.
