Lecture 1: Plant Reproduction

Prokaryotes

- Single-cellular
- No membrane-bound organelles
e.g. Bacteria, Archaea

Eukaryotes

- Mostly multicellular
- Membrane-bound organelles
e.g. Eukarya -> Plantae, Fungi, Animalia, Protista

Phylogenetic tree

- Based on DNA sequences of rRNA genes and other genes
- Most lineages consist solely or mainly of single-celled organisms
- Asterisks represent DNA from cellular organelles (mitochondria, chloroplasts)
- Eukarya is dominated by multicellular organisms

Endosymbiotic theory

- Mitochondria evolved before plastids through a sequence of events
- Ancestors of mitochondria were oxygen-using non-photosynthetic prokaryotes
- Ancestors of chloroplasts were photosynthetic prokaryotes
- Endosymbionts became organelles

Evidence supporting endosymbiotic origin of mitochondria and plastids

- Inner membranes are similar to plasma membranes of prokaryotes
- Organelles transcribe and translate their own DNA
- Divison and DNA are similar in organelles and prokaryotes
- Their ribosomes are more similar to prokaryotic than eukaryotic ones

Why are plants important?

- Oxygen
- Food, drink, animal feed
- Pharmaceuticals
- Fiber (cotton, wood)
- Fossil fuels
- QOL

Linnaeus

Linnean hierarchical classification: DKPCOFGS
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Genera (genus pl.) are grouped into families

Name = genus + "aceae"
-"aceae" means plant family
e.g. Poaceae: Grass family
e.g. Asteraceae: Sunflower family
e.g. Brassicaceae: Mustard family
*DON'T MEMORIZE

Plant relationships and classification

- Organisms are given unique Latin names
- Allows for systematic accumulation of knowledge
- Important for trade and commerce

Latin binomials

Genus + species + Authority
- All italicized
- Genus capitalized
- Authority: First to describe and name organism
e.g. Chenopodium album L.
- Chenopodium: Genus
- album: Species
- L.: Carl Linnaeus

em.

- Em = Emendates = Amended
- e.g. Triticum aestivum L. em. Thell.

Species

- Can interbreed + produce fertile offspring without artificial intervention

Subspecies (spp.)

- Capable of interbreeding and producing fertile offspring

Cultivar (cv.)

- CULTIvated VARiety
- Recognized subpopulation cultivated by us

Exceptions: Intergenic hybrids

- Fertile progeny involving two genera
- Requires intervention:
- Embryo rescue
- Bridge-crossing, chromosome doubling
- Cell fusion
Nomenclature:
- New genus is a combined name of the two genera
- X is used to indicate genus cross
e.g. xHeucherella
- Cross of Coral bells + Foam flower = Foamy bells

Plant reproduction

We will focus on the phylum Magnoliophyta (angiosperms, flowering plants)

Angiosperms

- Angiosperm means "closed seeds"
- Unique features: (3Fs):
- Flowers
- Double fertilization
- Fruity
- Adapted to most environments in the world, except for extreme cold
- Make up ~90% of the plant kingdom
- Divided into monocots and dicots

Types of angiosperms

Monocots
- One cotyledon
- Flower parts in multiples of 3
- Parallel veins
- Primary root replaced by adventitious root (fibrous root system)
- Scattered vasculature, no secondary growth
- One pore (furrow) on pollen grain
Dicots
- Two cotyledons
- Flower parts in multiples of 5
- Network of veins
- Primary root can persist (tap root)
- Ring formation in vasculature, with secondary growth
- 3+ furrows on pollen grain

Life cycles alternate between

Diploid (2n) generation, and haploid (n) generation

Sporophyte generation (2n)

• Most familiar plant parts

• Produce haploid (n) spores through MEIOSIS

• Spores grow into gametophytes

Gametophyte generation (n)

• Some plants grow in this state

• Produce haploid gametes through MITOSIS

• Fusion of gametes (fertilization) produces diploid sporophyte