Plant reproduction Flashcards
Name the male parts of a flower?
The anther and filament, together called the stamen.
Name the female parts of a flower?
Stigma, style, ovary, ovule. Together called the carpel.
What is the function of the filament in a flower?
Contains the xylem and phloem that supply the anther.
What is the function of the anther?
To produce pollen.
Describe/draw a cross section of an anther?
The anther should contain four pollen sacs. Each pollen sac is surrounded by tapetum, a food store providing energy for future cell divisions. Around this is a fibrous layer, then a protective epidermis.
What is the term for an anther splitting to release the pollen?
Dehiscence.
Give the steps of pollen formation?
Diploid pollen mother cells divide by meiosis to form a tetrad of haploid microspores. Microspore nucleus divides by mitosis forming a tube nucleus and a generative nucleus. Intine and exine layers develop around the cell. This is now a pollen grain.
Name the eight nuclei in the pollen sac and give their position?
Three at the top are antipodal, two in the middle are polar, two synergids and an egg cell at the bottom.
Give the steps in embryo sac formation?
A mother megaspore cell divides by meiosis to form 4 haploid megaspore cells. Three degenerate, one survives and goes through three rounds of mitosis.
Name the walls around the ovule?
Inner and outer integument.
Name the stalk that connects the ovule to the ovary?
The funicle.
Name the hole at the bottom of the ovule that the pollen tube enters through?
Micropyle.
How are flowers adapted for insect pollination?
Pollen is barbed to hook onto insect fur. Nectar, a scent, and brightly coloured petals. Sticky stigma.
How are flowers adapted for wind pollination?
Pollen is small, smooth and light, produced in large numbers. No scent, no nectary, small green petals. Feathery stigma and exposed anthers.
What are cross and self pollination?
Cross pollination is when pollen travels from the anther of one plant and lands on the stigma of another. Self pollination is when the pollen lands on the stigma of the same plant.
What are the advantages and disadvantages of cross pollination?
Advantage is that it increases genetic variation, which helps species adapt to changing environments. However, self pollination is more suited to a stable environment.
How do plants prevent self pollination?
Having the stigma above the stamen, having them mature at different times, genetic incompatibility, or separate male/female flowers or plants.
What is pollination?
When pollen lands on the stigma.
What happens after pollination?
The pollen germinates to produce a pollen tube, which digests a path down the style to the ovary. The generative nucleus divides by mitosis to produce two male gametes.
What is the function of the tube nucleus in pollen?
To control the growth of the pollen tube and code for production of hydrolytic enzymes.
What is double fertilisation?
When the tip of the pollen tube bursts, one male nucleus fertilises the egg, forming the diploid zygote. The other fertilises the two polar nuclei, forming the triploid endosperm.
What is the function of the endosperm?
It is a storage tissue that normally provides nutrients to the developing embryo.
After fertilisation, what do the ovule, ovary, funicle and integuments become?
The ovule becomes the seed, ovary the fruit, funicle leaves a scar called the hilum, integuments become the testa.
Which part of the embryo forms the root, and which part the shoot?
Radicle becomes the root, plumule the shoot.
What are the two possible food stores of a seed?
The endosperm or the cotyledons.
What are the two groups flowering plants are divided into based on their seeds?
Monocotyledons and dicotyledons.
List four ways seeds can be dispersed.
Wind, water, mechanical, animals.
Give the three conditions seeds need for germination.
Water, oxygen, suitable temperature.
Why do seeds need to imbibe water to break down food reserves?
Water activates the gene coding for gibberellin. Gibberellin diffuses to the aleurone layer and causes production of amylase, which breaks down the starch in the food store to maltose.
Why do seeds need to imbibe water to respire aerobically?
When water is imbibed through the micropyle the cotyledons swell and the testa split to allow entry of more oxygen for aerobic respiration.
What happens to a seed planted too deep in the soil?
It will use its full food store before the leaves reach the surface to photosynthesise.
