Chapter #2 - 3
Sexual Reproduction in Plants
Seed - reproductive package that contains an embryo, food supply,
seed coat – product of sexual reproduction
Angiosperms – flowering plants – seeds form inside flowers, when
mature the seeds are enclosed in case (pod or shell)
Gymnosperms – do not produce flowers - produce seeds inside cones
- a coat protects from dehydration - not enclosed inside a case
Pollination and Fertilization in Angiosperms
- Some produce large showy flowers while others produce tiny
flowers that are often not seen
Pistil - female reproductive organ
Stamen - male reproductive organ
Pollination - pollen grains from anthers on stamen reach stigma of
pistil - pollen grain must grow a pollen tube to reach ovule for
fertilization to occur
Self-pollination - male and female gametes come from same plant
Cross-pollination - gametes from 2 different parent plants – pollen
from one anther is transferred to stigma on different plant
Agents of cross pollination = wind, insects, animals
Self-pollination - male and female gametes come from same plant
Cross-pollination - gametes from 2 different parent plants – pollen
from one anther is transferred to stigma on different plant
Agents of cross pollination = wind, insects, animals
Seed Development in Angiosperms
- While pollen tube is growing, cells inside ovule begin preparation
- Sperm fertilizes egg - zygote
- Other cells in ovule have developed into cotyledon which contains
stored food
Zygote – mitotic division – form many celled embryo with miniature
leaf, root, stem
Fruit - Developing seed surrounded by walls of ovary which matures
to form fruits (pod or case around seed)
Seed Dispersal in Angiosperms
Fruit often aids in dispersal – seeds not digested - droppings
Launch - some able to project their own seeds
Hitch - cling to furry animals - fall off when rubbed or removed
Wind - fluffy sails that are easily swept away by wind
Water - run off of rain carries seeds that fall on ground
Dispersal – decreases competition with parent plant
Fruit often aids in dispersal – seeds not digested - droppings
Launch - some able to project their own seeds
Hitch - cling to furry animals - fall off when rubbed or removed
Wind - fluffy sails that are easily swept away by wind
Water - run off of rain carries seeds that fall on ground
Dispersal – decreases competition with parent plant
Germination and growth in Angiosperms
- process in which a seed begins to grow
- some seeds remain dormant or inactive for years and only
germinate when they encounter favourable conditions
Sexual Reproduction in Gymnosperms
- Gymnosperms do not bear flowers - have cones and often
called conifers
- male cones (pollen) and female (ovule) - in some species
male and female cones are produced on separate trees
- most have both types of cones on same tree
- Seed of gymnosperm contains an embryo, food supply, coat that
protects from drying out
- Seed not contained in a fruit
Sexual Reproduction in Gymnosperms
- Gymnosperms do not bear flowers - have cones and often
called conifers
- male cones (pollen) and female (ovule) - in some species
male and female cones are produced on separate trees
- most have both types of cones on same tree
- Seed of gymnosperm contains an embryo, food supply, coat that
protects from drying out
- Seed not contained in a fruit
Sexual Reproduction in Plants without Seeds
- Mosses, ferns, liverworts reproduce without seeds – use spores
- Spores are haploid but a spore can develop into a new plant
body without fertilization
Sporophyte – fine stalks – haploid – produce spores
Gametophyte – under right conditions spore develops into a
gametophyte that produces gametes
Spores – very light - carried great distances - survive unfavourable
temperatures and droughts (stay dormant for long periods of time
and still produce healthy plants when conditions are better)