plant reproduction

asexual reproduction

• most plants cells are totipotent

• vegetative reproduction

  • stolon/ rhizome

  • bulbs, tubers, corms

  • adventitious roots

  • suckers (new shoots arise from roots)

  • plantlets

• apomixis: seeds produced without fertilization

asexual reproduction advantages

very efficient

asexual reproduction disadvantages

genetically similar populations are more likely to succumb to diseases

sexual reproduction in plants 

based on meiosis and fertilization 

meiosis

is nuclear division that halves the chromosome number of the haploid number of chromosomes 

• independent assortment and recombination 

fertilization

the fusion of haploid gametes that produces a diploid zygote 

sperm

male gametes that contribute genetic information (DNA), but few or no nutrients, to the offspring 

eggs

female gametes that contribute both DNA and a store of nutrients to the offspring

angiosperms

a plant that has flowers and produces seeds enclosed within a carpel

The plant contains three basic sexual reproductive structures

1. the flower produces the gametes and develops seeds and fruit

2. the seed consists of the embryo and nutrient stores 

3. the fruit develops from the flower (ovary tissue) and contains the seeds

general structure of the flower

four basic organs that are essentially modified leaves: 

1. sepals 

2. petals

3. stamens 

4. carpels 

perfect flowers

contain both stamens and carpels (bisexual flowers)

imperfect flowers

contain either stamens or carpels

monoecious plants

have sperate stamen- and carpel- producing flowers on the same individual

dioecious plants

have either stamen or carpel-producing flowers on different plants 

pollination 

the transfer of pollen grains from an anther to a stigma 

fertilization

occurs when a sperm and an egg unite to form a diploid zygote 

plants that do not form pollen  

sperm must swim to the egg or are otherwise transferred to the egg through water 

gymnosperms

rely on wind for pollination

insect pollination

an important adaptation because it makes sexual reproduction much more efficient

animal pollination is a mutualistic relationship

pollinators benefit by receiving food and flowering plants benefit because of outcrossing

fertilization triggers the development of a young sporophyte

the mature seed consists of three parts 

1. embryo

2. endosperm

3. seed coat

3 basic fruit types

1. simple

2. aggregate

3. multiple

2 basic functions of fruit 

1. protection of the seeds

2. seed dispersal 

seed-free plants

• bryophytes( mosses, liverworts, hornworts)

• seed-free vascular plants (lycophytes and ferns)

• fertilization via swimming sperm (water required)

where does meiosis occur in angiosperms

ovary

where does meiosis occur in angiosperm flowers

anthers