Reproduction In Plants Flashcards
What is asexual reproduction?
The process resulting in the production of genetically identical offspring from one parent, without the fusion of gametes
What is sexual reproduction?
The process involving the fusion of two haploid gametes to form a diploid zygote. It produces genetically dissimilar offspring
What happens during asexual reproduction and how many chromosomes does the daughter cell have
The cell divides to produce two identical daughter cells through mitosis. Each daughter cell has the same number of chromosomes as the parent plant
What happens during sexual reproduction and how many chromosomes does the daughter cell have
A haploid male gamete fuses with the haploid female gamete in a process called fertilisation. The nuclei of the two haploid gametes fuse to form a diploid zygote. Gametes are formed when a cell divides to produce 4 daughter cells through meiosis. Each daughter cell has half the number of chromosomes as the parent cell
What are the parts of a flower
Sepal
Petal
Receptacle
Pedicel
What is a sepal
A modified leaf that protects the flower in the bud stage
What is a petal
A modified leaf that forms the most obvious part of the flower. All petals together make up the corolla. And in insect pollinated flowers the petal is brightly coloured to attract insects for pollination and provide a landing platform for insects
What is a receptacle
The enlarged end of the flower stalk
What is a pedicel
The flower stalk
What is the stamen and what are its parts
Male part of the flower; consists of filament and anther
What is the function of the filament
To hold the anther in a suitable position to disperse pollen grains
What is the function of the anther
To produce pollen grains for pollination.it is made up of two lobes , each containing 2 pollen sacs. Male gametes in pollen grains produced by meiosis has a haploid set of chromosomes.
What is in each pollen grain?
A male gamete( generative nucleus; involved in fertilisation) and the pollen tube nucleus
What are the parts of a carpel/pistil?
Stigma
Style
Ovary
Ovule
What is the function of the stigma ?
Receives pollen grains. A mature stigma secretes sugary fluid to stimulate the germination of pollen grains
What is the function of the style?
Holds the stigma at a suitable position to trap pollen grains
What is the function of the ovary?
Produces and protects one or more ovules. Will develop into a fruit after fertilisation
What is pollination?
The transfer of pollen grains from the anther to the stigma
What is the importance of pollination?
It helps bring together the male and female gametes to enable fertilisation to take place
What are the two types of pollination
Self pollination and cross pollination
What is self pollination?
The transfer of pollen grains from the anther to the stigma of the same flower or a different flower of the same plant
What are the characteristics of self-pollinated plants?
Flowers are bisexual with the anthers and stigmas maturing at the same time
Stigma is situated directly below the anther
What are the advantages of self-pollination?
- beneficial qualities are passed down from the parent to the offspring
- only one parent is required
- less pollen and energy is wasted
- more likely to take place as stigmas are closer to the anthers
- not dependent on external actions for pollination
What are the disadvantages of self-pollination?
Offspring produced are genetically similar to parents causing fewer varieties of offspring
Probability of harmful recessive alleles being expressed in offspring are higher as compared to cross pollination
What is cross pollination?
The transfer of pollen grains from the anther to the stigma of a flower of another plant of the same species
What are the advantages of cross-pollination?
Offspring can inherit beneficial qualities from both parents
More varieties of offspring are produced which leads to a greater genetic variation
Increased probability of offspring being heterozygous
Seeds produced are capable of surviving longer before germination
Probability of harmful recessive alleles being expressed in offspring are lower as compared to self-pollination
What are the disadvantages of cross-pollination?
Two different plants of the same species are required
Dependent on external factors like wind and insects for pollination
More energy and pollen are wasted
Less likely to occur as compared to self-pollination
What is an example of an insect-pollinated flower?
Clitoria
What are the characteristics of the clitoria
The filaments of 9 stamens are fused to form a trough that encloses the pistil
Nectar of the flowers collects at the bottom of the stamen trough, only insects with a long tubular mouth can reach it
The stigma is small and compact
The style is long, curved and hairy
It contains nectar guides
What happens when the insect lands on the standard petal of the clitoria
It follows the nectar guides into the flower
And forces its way in between te 2 wing petals to collect nectar
The insects back forces the keel petal upwards to expose the anthers and stigma.
Pollen grains from the anther stick to the back of the insect and get transferred to a stigma
When the insect leaves the flower, the keel petals spring back to its original position
What is an example of a wind-pollinated flower?
Ischaemum muticum
What are the characteristics of the ischaemum muticum
It’s flowers come in pairs
Each flower is enclosed by 2 flowering bracts
The upper bisexual flower consists of an ovary, 2 long feathery stigmas, 3 stamens and 2 lodicules
When ready to reproduce the lodicules swell and force the two flowering bracts apart
The lower male flower contains only 3 stamens with long filaments and 2 lodicules
Mature stamens have long filaments that hangs downwards and can swing freely(pendulous)
When the filaments sway the pollen is shaken free and carried away by the wind
A mature stigma is large extended and feathery to provide a large surface area for the capture of pollen floating in the air
What are the differences between insect ad wind pollinated flowers?
Petals : large and brightly coloured (insect) l small dull-coloured and without petals (wind)
nectar: is present (insect) l is absent (wind)
Scent: fragrant and sweet-smelling (insect) l scent is absent in flowers (wind)
Stigmas: small compact and do not protrude out of flowers (insect) l large feathery and protrude out of flowers (wind)
Stamens: not pendulous and do not protrude out of flowers(insect) l long and pendulous filaments with protruding anthers (wind)
Pollen: fairly abundant. Pollen grains are larger with rough surfaces (insect) l more abundant. Pollen grains are tiny with smooth surfaces
Nectar guides: present (insect) l absent (wind)
What happens during fertilisation in plants?
Pollen grain germinates in response to the sugary fluid secreted by the mature stigma
A pollen tube grows out of the pollen grain
The male gamete (generative nucleus) enters the pollen tube
The pollen tube secretes enzymes that digests the tissues of the stigma and style. Thus the pollen tube grows down the style into the ovary
Pollen tube enters the ovule through the micropyle
When the pollen tube reaches the ovule, its tip absorbs sap and bursts, releasing the male gamete
The haploid male gamete fuses with the ovum to form the diploid zygote. This is fertilisation. The zygote divides and develops into the embryo
