Sexual & Asexual Reproduction In Plants (chpt. 39 & 40) Flashcards
Female parts of plant
Carpel
• stigma
• style
• ovary
Male parts of plant
Stamen
• anther
• filament
Role of stigma
Captures pollen
Role of style
Connects stigma to ovary
Role of ovary
Site of fertilisation , produces the ovule
Role of anther
Produces male gametes (pollen grains)
Role of filament
Supports anther and supplies it with food and water
Role of sepal
Protects the bud
Role of petal
Attract animal pollinators
↳ brightly coloured and scented
Where are the male gametes found?
In the pollen grains
Male gamete formation → steps
• anther consists of 4 pollen sacs containing diploid microspore mother cells
• divide by meiosis to produce 4 haploid cells which join to form tetrad
• tetrad breaks up and forms 4 microspores
• microspore divides by mitosis to produce 2 haploid nuclei → generative nucleus and tube nucleus
Female gamete formation → steps
• diploid megaspore mother cell in ovule divides by meiosis to produce 4 haploid cells → 3 degenerate and 1 survives as megaspore / embryo sac
• embryo sac undergoes mitosis 3 more times to produce 8 haploid nuclei → 5 die, 2 form polar nuclei, 1 forms egg
Female gametes: 1 egg + 2 polar nuclei
Pollination
Transfer of pollen from an anther to a stigma of a flower of the same species
Cross-pollination
Pollination of another plant of the same species
↳ more variation & greater strength
Self-pollination
Pollination of a plant by itself
↳ less variation
Features of an animal pollinated plant
Large bright scented petals
Sticky stigma
Features of a wind pollinated plant
Large quantity of light pollen produced
Long stamen outside flower
Long feathery stigma
Fertilisation
The fusion of male and female gametes to form a diploid zygote
Steps in fertilisation
• pollen grain lands on stigma
• tube nucleus forms pollen tube which grows down the style to the ovule
• generative nucleus divides by mitosis to form 2 sperm nuclei
• double fertilisation occurs:
Sperm nucleus + egg nucleus → zygote (2n)
Sperm nucleus + 2 polar nuclei → endosperm (3n)
Which part of seed develops into the shoot?
Plumule
Which part of seed develops into the root?
Radicle
Function of testa
Protects embryo