Plants reproduction

Pollination

Angiosperms

Self-fertilization

act of placing of pollen (containing male gametophyte) on the stigma of a carpel

male gametophyte will then travel to female gametophyte (inside embryo sacs located inside ovule)

plants usually transfer pollen to a different flower

use flowers, double fertilization and fruit in sexual reproduction

sepals- protect floral bud

petals- attract pollinators

stamens- anthers are site where haploid microspores develop into pollen grains containing male gametophyte

carpels- ovules (immature seeds) contained in their swollen bases

Complete flowers have all four basic floral organs

Incomplete flowers lack at least one of the basic floral organs- some are sterile or some are unisexual

Inflorescenses showy clusters of flowers and much of this diversity represents adaptations to specific pollinators

Types of pollination:

  1. Self-fertilizing- see in some crop plants

Abiotic pollination- wind

Biotic- insects

plants being able to combine their own pollen and ovule to form a zygote-
good b/c it ensures every ovule will develop into a seed

  • bad b/c it doesn't increase genetic diversity

self-incompatibility- ability of plant to reject its own pollen and pollen of closely related individuals

union of two sperm cells with different nuclei of female gametophyte

1 sperm fertilizes egg and 1 sperm fertilizes 2 polar nuclei

Seeds- the result of double fertilization

after double fertilization each fertilized ovule develops into a seed and each ovary develops into a fruit enclosing the seed

Seed= embryo (2n) + endosperm (3n)

in eudicot plants, the endosperm's stockpile is exported to the cotyledons (seed leaves) before the seed completes development

seed enters dormancy- stops growing and metabolism nearly ceases

seed coat formed from integuments of ovule protects embryo and its food supply

Environmental conditions to break seed dormancy

Inhibition- uptake of water by dry seed due to its low water potential

Structure of seeds:

  1. Embryo- elongated structure
  2. cotyledons- attach to embryo
  3. hypocotyl- under point where cotyledons attach to embryo
  4. radicle- embryonic root
  5. epicotyl- above where cotyledons attach and below first mini leaves
  6. plumule- epicotyl + young leaves + shoot apical meristem

Eudicot- angiosperm plant named for the 2 cotyledons it possess

Asexual reproduction

generation of offspring from a single parent that occurs without the fusion of gametes

can occur by budding, division of single cell, or division of entire organism into two or more parts

Vegetative reproduction

fragmentation- detached fragment of plant that can develop into a whole new plant

apomixis- plants can sometimes produce seeds without pollination or fertilization

PROS:

  • no need for pollinator
  • offspring can have desirable genomes
  • generally stronger progeny
  • less "costly" for parents' resources

CONS:

  • parent and offspring have identical genomes
    (bad if environment changes)
  • offspring not dispersed as far away
  • offspring must grow in current environment, whether its favorable or not