35. Plant Reproduction Flashcards
Sexual reproduction def.
Involves 2 sex cells/gametes joining together
5 stages of plant reproduction
(Pretty Flowers For Dreamy Girls)
- Pollination
- Fertilisation
- Fruit and Seed Formation
- Dispersal
- Germination
Function of
Sepal
Petal
Sepal: Green leaf like structure, protects flower whan it is a bud.
Petal: Protects inner parts of flower.
Function of Carpel Stigma Style Ovary
Carpel: Produce female gamete: egg
Stigma: Catches pollen
Style: Pollen transported to ovary
Ovary: Produces egg (female gamete)
Function of
Anther
Filament
Stamen
Anther: Produces pollen (male gamete)
Filament: Supports anther and ensures that anther is located up high so pollen can leave easily.
Stamen: Produces pollen grain which contains pollen
Pollination def.
Is the transfer of pollen from the anther to the stigma
Self pollination
Transfer of pollen from an anther to the stigma of the same plant.
Cross pollination
Transfer of pollen from an anther to the stigma of a different plant
Methods of pollination
Wind and Animal
Characteristics of Wind pollinators
and examples
Small green petals
Large amounts of pollen
Stamens and carpels hang outside in wind
Examples: Grass, oak, hazel
Pollen sac structure
Outside - In
Fibrous layer-protection
Tapetum- provides energy for dividing of pollen sac to produce pollen grains
Pollen mother cells: produce pollen grains
Pollen grains
How many pollen sacs in an anther
4
How a pollen grain develops
from start to before pollination
1 Microspore mother cell *Divides by meiosis* 4 Haploid cells-cluster called tetrad *seperate* Pollen grains with n nuclei *mitosis* Generative nucleus and Tube nucleus
Structure of pollen grain
Exine: Outer spikey coat
Intine: Smooth inner coat
Function of tube nucleus and generative nucleus
Tube: Forms pollen tube
Generative: Forms male gamete
What happens to pollen grain after pollination
Generative nucleus (n) divides by mitosis to form 2 pollen/male nuclei (n) Tube nucleus doesn't divide but forms pollen tube. Pollen nuclei travel down tube
Female gamete formation- where
Ovule in ovary
Ovary structure and function
Microphyle: where pollen tube enters
Nucellus: provides nutrients for growth
2n Nucleus: Megaspore mother cell divides to produce egg
Female gamete formation-what happens
1. Megaspore mother cell (2n) divides by Meiosis to form 4 haploid cells. 3 haploid cells degenerate Remaining cell called embryo sac (n) 2. Nucleus of embryo sac divides by mitosis 3 times = 8 haploid nuclei 5 of these nuclei disintegrate remaining 3 are gametes 1 = egg cell 2 = polar nuclei
Fertilisation def.
The fusion of the male and female gametes (n) to produce a zygote (2n)
Plants carry out double fertilisation
Where does fertilisation take place
In the ovule of the ovary in the carpel
Fertilisation process
- pollen grain lands on stigma
- Pollen tube grows down style
- Generative nucleus travels down pollen tube and divides by mitosis to produce 2 pollen nuclei.
- Pollen tube enters ovule via micropyle. Tube nucleus degenerates
- Pollen nuclei enter ovule.
- 1 fuses with egg = 2n Zygote
Other fuses with 2 polar nuclei = 3n Endosperm
What does the fruit form from
the ovary
Fruit def.
A mature ovary that may contain seeds
Fruit formation
wall of ovary becomes wall of fruit-pericarp
when fruit fully formed flower wilts and falls away leaving just fruit.
Stimulated by growth regulators produced in seeds
Types of fruit
- Seedless
- Fleshy
- Dry
- Grains
- False fruits
Seedless fruit
how formed
examples
- Genetically: naturally or by special breeding program. Eg. Seedless grapes
- Growth regulators: If large amounts of growth regulators (auxins) are sprayed on flowers fruits may form without seeds. Eg. Cherries
What are false fruits and example
Fruit that dont develop from the ovary but from other parts of plant.
eg. strawberries develop from swollen receptacle
Examples of fruit
Dry
Fleshy
Grains
Dry: pea pods, green beans
Fleshy: Plums, peaches
Grains: Cereals, Barley, Maize
Types of seeds
- Endospermic or non endospermic
2. Monocots or Dicots
What do seeds form from
and what does outer coat of seed form from
Ovule in ovary
Outer coat: Integuments- called testa
Structure of ovule- labelling
In ovary 2 walls - integument opening between integuments: micropyle Inside of ovule: Nuclellus Inside ovule is 2n Megaspore mothercell
All seeds have
Some seeds have
All seeds have: An embryo and a testa
Some seeds have: an endosperm
What is the embryo
embryo- immature plant developed from zygote dividing by mitosis
Embryo structure consists of
- Plumule: immature shoot
- Radicle: immature root
- Cotyledon: seed leaf or food supply
Endosperm
forms from
function
seeds with it known as
Forms from: 3n endosperm dividing by mitosis
Function:
Seeds with it known as: endospermic seeds
What is a non endospermic seed?
Endosperm used up in early stages of seed development. Food stored in cotyledon
Dispersal def.
The carrying of the seed as far from the parent plant as possible
Importance of Dispersal
- Minimises competition for light, water etc.
- Avoids overcrowding
- Colonises new areas
- Increases chances of survival
Methods of dispersal
Wind
Water
Self
Animal
Wind dispersal characteristics
Small and light.
Sycamore- has wings
Dandelion- has parachute
eg. Dandelion, sycamore, ash, thistle
Water dispersal characteristics
Able to float
Light
eg. coconuts, water lilies, alder
Self dispersal characteristics
fruit burst open when ripe
seeds flung away as far as possible
eg. beans and peas
Animal dispersal characteristics
Edible: bright colours, good smells and taste. Passes through digestive system of animal and is passed out.
eg. Strawberries, blackberries, nuts
Sticky: have hooks to cling to animal hair.
eg. burdock, goose grass (sticky ball)
Dormancy def.
A resting period when seeds undergo no growth and have reduced cell activity and metabolism
Advantages of dormancy
- Plants avoid harsh weather conditions
- Gives embryo time to develop
- Provides time for dispersal
Applications in horticulture
- Some seeds need a period of cold before they germinate- farmers use this for successful germination
- Knowing seeds undergo dormancy allows farmers to break dormancy in some plants before they are planted.
How to break dormancy
- Soak seeds in water
2. Break the testa physically
Germination def.
The regrowth of the embryo after a period of dormancy into a new plant, if environmental conditions suitable
What factors are needed for germination and why
- Water: To transport dissolved nutrients. Needed as a reactant in respiration
- Oxygen: for respiration to occur-for energy for growth
- For optimum environment for enzymes
Graph of mass of embryo vs. Endosperm over time
Embryo increases in mass over time.
Endosperm decreases in mass.
Germination process for sunflower (Epigael)
Water absorbed through micropyle. Radicle emerges Lateral roots develop. Hypocotyl hook emerges from radicle. Plumule grounds and new leaves develop. Radicle grows downwards Seed discarded (Think sunflower-sun-above ground) In epigeal germination-cotyledons rise above ground.
Germination process for broad bean (hypogeal)
Seed absorbs water through micropyl for respiration and to activate enzymes.
Radicle emerges and grows into roots
Plumule emerges.
Plumule is hooked to protect the leaves at the tip.
Plumule grows above the surface of the soil.
Lateral roots develop.
Plumule straightens and leaves open.
Cotyledon stays below the surface.
Seed shrivels as food has been used.
Hypo= low
What is the epicotyl
space between the seed and the plumule
