D3.1 - plant reproduction (5i) Flashcards
what are the elements of a flower reproductive system?
- Anther
- Filament
- Septal
- Nectary
- Petal
- Stigma
- Style
- Ovary
what is the role of the anther?
produces and releases the pollen grains, which contain the male nuclei
what is the role of the filament?
holds up the anther
what is the role of the petal?
colorful to attract pollinating insects
what is the role of the stigma?
sticky region that receives the pollen
what is the role of the style?
supports the stigma
what is the role of the nectary?
produces sweet nectar to attract pollinating insects
what is the role of the ovary?
containing ovules, where the female nuclei develop
what is the role of the sepal?
protects the developing flower, while it is in the bud
what is the process of sexual reproduction in flowering plants?
reproduction in flowering plants is sexual, even if a plant species is hermaphroditic e.g) sunflowers and orchids
- production of haploid gametes using meiosis.
- ovules (female gametes) are produced in the ovary
- pollen grains (male gametes) are produced in the anthers - pollination - transfer of pollen between flowers from anther to stigma
- the pollen grain grows into a structure called a pollen tube, which penetrates down the style
- the pollen tube delivers the male reproductive nuclei to the female nuclei within the ovules inside the ovary of a flower
- fertilization - fusion of male and female nuclei to produce an embryo
- seed develops from fertilized ovule, while fruit develop from the whole ovary
- seed dispersal - seeds are distributed away from the parent plant via self-explosion, wind or animals
- seeds germinate when conditions are appropriate
what is cross-pollination?
cross pollination is the transfer of pollen produced on one plant to another plant
what is the impact of cross-pollination?
cross pollination increases genetic variation within a species
what impact does self-pollination have on a plant species?
self-pollination leads to inbreeding, which decreases genetic diversity and healthy growth
What does hermaphroditic mean?
contains both male and female structures and is able to fertilise itself can reproduce
what are 4 methods of preventing self-pollination?
- different maturation times for pollen and stigma or ovules
- genetic mechanisms where protein interactions occur when pollen lands on the stigma within the same plant, preventing reproduction from continuing in a variety of different ways
- having separate male and female flowers on a plant
- having separate male and female plants within a species
what are the roles of wind and insects in cross-pollination?
wind pollination
- often transfers pollen away from a parent plant
- animal pollinators are not needed, an no pollen is eaten by those animals
insect pollination
1. glands in the nectary at the base of the ovary in a flower secrete sugary liquid that attracts pollinators
2. pollen from the anther sticks to the animal when it enters the flower
3. pollen is received by the sticky stigma on the same or another flower
mutualistic relationship as the animal gets nectar and the flower gets pollinated.
what are key features of pollination?
- movement of pollen, containing male gametes
- movement from anther to stigma
- necessary for fertilization and sexual reproduction
- if animals eat the pollen, it gets destroyed
what are key features of seed dispersal?
- movement of seeds, contained within fruits
- movement away from the parent plant
- necessary for germination and colonization of a new area, avoiding intraspecific competition for nutrients
what are similarities between pollination and seed dispersal?
- movement can involve self-explosion, wind or animals
- animals may assist movement through pollen/seeds sticking to their fur
- animals may be attracted through sweetness and colour (to petals/fruit)
what is fertilization?
fusion of male and female nuclei to produce an embryo
what is germination?
growth and development of the embryo, and the mobilization of food reserves
what are the requirements of the correct conditions to allow germination to occur?
- water - rehydrates the seeds, causing swelling and bursting of testa (seed coat)
- oxygen - used in aerobic respiration to produce energy
- suitable temperature - enzyme-catalysed reactions require warmth to increase kinetic energy and the rate if molecule collisions
- suitable pH of soil - prevents denaturation of the enzymes that control the metabolic events of germination
what are the metabolic events of germination in a typical starchy seed?
- water is absorbed through the micropyle to rehydrate the seed.
- this activates metabolism, causing the hormone gibberelic acid to be produced in the embryo, which stimulates the production of amylase.
- this enzyme catalyses the breakdown of starch to maltose.
- the maltose diffuses to the embryo root (radicle) and shoot (plumule) where it is hydrolysed to glucose and used to release energy through aerobic respiration and converted to a range of biological molecules to be used for growth.
- growth and development of the embryo occurs;
- growth of the radicle downward
- growth of the plumule upwards
- cotyledons are raised
- a true leaf emerges between the cotyledons, allowing photosynthesis to occur to further support growth and development
why does the embryonic plant lose biomass?
initially, the dry mass of a plant embryo decreases over time, because the rate of respiration is higher than that of photosynthesis
in what conditions is a plant no longer considered to be embryonic?
once the rate of photosynthesis exceeds the rate of respiration, the plant gains dry mass and it is no longer considered an embryo
what are structures within a starchy seed from an internal view?
testa - tough, protective outer coat
radicle - embryonic root ending in an apex
plumule - embryonic shoot with embryonic leaves
cotyledon - seed leaf for nutrient storage
