Chapter 38 Angiosperm Reproduction Background The sporophyte generation

Chapter 38: Angiosperm Reproduction

Background - The sporophyte generation is the dominant generation in the life of an angiosperm. - The stamens and carpels are the reproductive organs in a flower.

Background - Complete flowers- Have all of the basic flower parts - Incomplete flowers- Do not have all of the basic flower parts

Reproductive Organs • The anther and the ovule have sporangia located inside of them- this is where the gametophytes develop.

Gametes - Pollen Grains (male gametes) develop in the microsporangium - Order of events: Microsporangium a microsporocyte 4 microspores each microspore will develop into 1 pollen grain, each housing 2 sperm

Gametes - Embryo Sack (female gametes) develop in the megasporangium - Order of events: Megasporangium a megasporocyte 4 megaspores but only one will survive embryo sack

Pollination- Transfer of pollen from the anther to the stigma - The pollen forms a pollen tube down the stigma and style - Discharges the two sperm at the embryo sack - Self-incompatibility- Many flowers will reject pollen from itself (promotes genetic diversity)

Fertilization- Formation of the embryo - Ovules develop into the seeds - Ovary develops into a fruit

Fertilization - One pollen = Two sperm = Double fertilization - Sperm #1 - Forms the zygote - Sperm #2 - Forms the endosperm (food storage material for the seed

Seeds Mature Seed: - Seed coat- Protection for the seed - Cotyledon(s)- “Seed leaves” - Endosperm- Food - Radicle- Embryonic root

Fruits: - Simple- Developed from a single carpel from one flower - Aggregate- Developed from multiple carpels from one flower - Multiple- Many carpels on many flowers

Germination • Seed germination- The start of a new plant - The seed can be dormant for many years until the conditions are ideal for growth - Imbibition- First step of germination. Uptake of water by the dry seed (hydration) - The radicle is the first part to emerge from the seed

Asexual Reproduction- Common in flowering plants IF the plant is living in ideal conditions - Vegetative reproduction- Fragmentation of the plant. A part is detached and starts a new plant. - Apomixis- Formation of a seed without pollination or fertilization

Asexual Reproduction - Grafting (done by man)- Attaching a twig or branch of one species to a different species - Stock plant- The plant who is providing the roots - Scion plant- The twig or branch grafted onto the stock.