Plant Reproduction

Title :

Plant Reproduction

Author :

Kim Foglia & Kelly Reidell

Number of slides:

29

Slideshow :

Content transcript :

Animal vs. Plant life cycle

Alternation of generations

Evolutionary trends

* Alternation of generations

* dominant haploid plant

* bryophytes - mosses

* dominant diploid plant

* pteridophytes - ferns 

* gymnosperm - conifers

* angiosperm - flowering plants

* Evolutionary advantage?

* reduction of gametophyte protects delicate egg & embryo in protective sporophyte

Gametophytes of seed plants

* male gametophyte

* pollen in male cone

* female gametophyte

* develops in female cone

* seed

* naked in cone

* male gametophyte

* pollen in anthers of flower

* female gametophyte

* develops in ovaries of flower

* seed

* protected in ovary

* ovary wall can develop into fruit

Angiosperm life cycle

Flowers 

Flower 

* Modified shoot with 4 rings of modified leaves

* sepals

* petals

* stamens

* male

* carpals

* female

Male & female parts of flower

Male Parts of flower

* Stamens = male reproductive organs

* stalks (filament) & terminal anthers

* pollen sacs produce pollen

* pollen grain = gametophyte

* sperm-producing structure

Female Parts of flower

* Female carpels = female reproductive organs

* Stigma = top of carpel

* Sticky

* Collects pollen 

* slender neck = style

* ovary at the base

* within the ovary are 1 or more ovules

* within ovules are embryo sacs

* female gametophyte = embryo sac

* egg-producing structure

Fertilization 

* Pollination

* Pollen grain produces a pollen tube

* pollen tube grows down style into ovary & discharges 2 sperm into the embryo sac

* 1 sperm fertilizes egg = zygote

* zygote develops into embryo

* ovule develops into a seed 

* ovary develops into a fruit containing 

1 or more seeds

* pollen released from anthers is carried by wind or animals to land on stigma

Preventing self-pollination

* Various mechanisms

* stamens & carpels may mature at different times 

* arranged so that animal pollinator won’t transfer pollen from anthers to stigma of same flower

* biochemical self-incompatibility = block pollen tube growth

Fertilization in flowering plants

* Double fertilization

* 2 sperm from pollen

* 1 sperm fertilizes egg = diploid zygote

* 1 sperm fuses with 

2 polar nuclei to form 3n endosperm

* endosperm = food tissue in seed

* coconut milk

* grains

Development of the new sporophyte

* Cotyledons = bumps on proembryo

* “seed leaf”

Structure & Function of the Seed

* Seed coat

* Protective layer around the seed

* Hypocotyl

* Below cotyledons

* Embryonic root

* Epicotyl

* Above cotyledons

* Embryonic shoot

From Seed to Seedling

* Imbition

* Uptake of water

* Enzymes digest endosperm

* 1st organ = root

* 2nd organ = shoot

Fruit 

* Fruit is a mature ovary

* seeds develop from ovules 

* wall of ovary thickens to form fruit

* fruits protect dormant seeds & 

aid in their dispersal

Fruit development

* peach

* 1 flower : 1 carpel : 1 ovary : 1 seed

Fruit development

* apple

* 1 flower : 5 carpels : many ovaries : many seeds

Fruit development

* Citrus fruit

* 1 flower : many carpels : many ovaries : many seeds

Fruit development

* Raspberry

* 1 flower : many ovaries : many seeds

Coevolution of plants & animals

* Angiosperms & animals have shaped one another’s evolution 

* Natural selection reinforced the interactions 

because they 

improved the 

reproductive 

success of 

both partners

Seed dispersal

* Plants produce enormous numbers of seeds to compensate for low survival rate 

* a lot of genetic variation for natural selection to screen

Asexual Reproduction

* Fragmentation

* Separation of parental plants into parts that develop into whole plants

* Apomixis

* Produce seeds without being fertilized

* Diploid cell produces embryo

Asexual Reproduction – Vegetative Reproduction

* Callus

* Undifferentiated cells that can make new plant from a cutting

* Grafting

* Combines best qualities of plants

* Test-tube plants

* Plantlets can be transferred into soil

Plant Biotechnology

* Maize

* Cannot spread own seeds

* Artificial selection 

* Bt. toxin

* Natural pesticide

* Put into cotton, maize, potatoes

* Herbicide

* Reduces need to weed

* Disease resistance

* Vitamin content

* Golden rice

* Gene containing beta-carotene (can make Vitamin A)

* Prevents blindness