Earth’s dominant plants Angiosperms Earth’s dominant plants

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

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

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

Reproduction Pollination Double Fertilization Germination 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  3n 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

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