Earth’s dominant plants

Angiosperm Characteristics
 Vascular  Dominant sporophyte generation
 Flowering plants
 Xylem – vessel elements
 Double fertilization
 Seeds are covered in a fruit
 Phloem – sieve tube elements

2 Largest Classes
Monocots
 Grasses, corn, palms
 Mainly herbaceous
 Parallel veins in leaves
 Flower parts – multiples of
3
 Seed – 1 cotyledon, endosperm
Eudicots
 Roses, sunflowers, maples
 Herbaceous or woody
 Branched veins
 Flowers – multiples of 4 or
5
 Seed – 2 cotyledons

Flowers
 Reproductive part of angiosperms
 4 parts: sepals, petals, stamens, carpels
 Complete vs. Incomplete flowers
 Perfect vs. Imperfect flowers

Reproduction
 Pollination

Wind

Water

Pollinators
 Double Fertilization
 Germination

What happens in the anther?
 Pollen sac contains many microsporocytes

Meiosis  4 haploid microspores
 Each microspore  pollen grain (immature male gametophyte
 Each pollen grain contains 2 cells:


Tube cell
Generative cell
 Anther splits – sheds pollen

What happens in the pistil?
 Each ovule in ovary contains megasporocyte

Meiosis  4 haploid megaspores


3 megaspores disintegrate
Remaining megaspore divides  gametophyte
(aka embryo sac)
 Gametophyte contains 7 cells w/ 8 nuclei

Egg cell contains 1 nucleus

Large center cell contains 2 polar nuclei

Double Fertilization
 Pollen lands on sticky stigma


Tube cell forms pollen tube through style into ovary
Generative cell divides  2 sperm cells
 Double Fertilization


1 sperm fertilizes egg  zygote  embryo
1 sperm fuses with both polar nuclei  3 n cell
 endosperm

Seed and Fruit Formation
 Ovule develops into seed
 Ovary wall enlarges

Ripens into fruit
 Flower parts fall off
 Fruits:


Protect seeds from dessication
Aid in dispersal

Success of Flowering Plants
 Seeds an advantage over spores
 Cross-pollination – increases variation
 Animals disperse pollen and fruit farther than wind

 Efficient xylem
 Vessel elements
 Broad leaves
 efficient photosynthesis
 Abscission

Reduces water loss
 Adaptability of sporophyte generation