3.8 Plant Reproduction

Reproduction in Angiosperms

• gametophytes are in flowers

• female gametophyte is enclosed structure - ovule

• double fertilization produces embryo & endosperm

• ovary tissues form fruit

• animal pollination is common

Reproduction in Gymnosperms

• gametophytes on separate cones

• female gametophyte is on bracts of female cone

• single fertilization produces naked seed

• wind pollination more common

Sexual Reproduction in Angiosperms

• occurs in flower fertilized by pollen

Perfect or hermaphroditic Flowers

• Both Male and Female Parts

Monoecious

• separate male & female flowers on same plant

Dioecious

• separate male & female plants

Flowers

• produced by mature sporophyte

• house gametophyte generation

• modified stems w/ modified leaves

Flower Structure

• flower whorls from outside to inside 

Flower Structure - Calyx

• outermost whorl made of sepals help to protect the bud

Flower Structure - Corolla

• second whorl made up of petals

Flower Structure - Androecium

• third whorl w/ male reproductive structures

Flower Structure - Gynoecium

• innermost whorl w/ female reproductive structures

Flower Reproductive Structures - Carpel

• female part of flower

• ovary - contains ovule

• stigma - tip for pollen landing

• style - neck or stalk leading to ovary

Flower Reproductive Structures - Stamen

• male part of flower

• anther - contains pollen grain

• filament - supports anther

Types of Flowers - Complete Flowers

• all 4 whorls are present

• not a perfect flower

Types of Flowers - Incomplete Flower

• missing at least one whorl

Types of Flowers - Perfect Flower

• contains both male & female parts

• Perfect flower = Complete flower

Types of Flowers - Imperfect Flower

• identified by structures that are present in the flower

• Staminate - only male structures are present

• Carpellate - only female structures are present

Male Gamete Production

• Microsporogenesis undergoes meiosis

• Microgametogenesis divide via mitosis

Female Gamete Production 

• megasporogenesis via meiosis > 4 megaspores (3 small, 1 large)

• megagametogenesis via mitosis to produce 8 nucleate, 7 celled gametophyte

Gamete Formation

• sporogenesis occurs via meiosis to produce spores

• gametogenesis occurs via mitosis to produce gametes

Pollination

• transfer of pollen from anther to stigma

• pollen grain grows pollen tube

Fertilization

• one sperm fuses w/ egg nucleus = diploid zygote

• one sperm fuses w/ two nuclei in central cell = triploid endosperm

Pollination - Self Pollination

• plant does not need to produce nectar for pollinators

Pollination - Insects

• shape of flower suits pollinator

Pollination - Bats

• flowers are large & bright

Pollination - Birds

• plants are sturdier than those pollinated by insects

Pollination - Wind

• flowers emerge before leaves

The Seed

• seed coat protects embryo

• endosperm stores food for developing embryo

The Seed - Embryo Structure

• cotyledons: leaves

• radicle: roots

• hypocotyl: stem

The Seed - Micropyle

• stays open as a pore for gas exchange

The Seed - Hilum

• scar on seed coat from attachment to ovary wall

The Embryo

• zygote develops from a single cell into an embryo

Monocot & Eudicot(dicot) Seeds

• Monocot: one cotyledon

• Eudicot (dicot): two cotyledons

Fruit Formation

• fruits = dispersal of seeds

Fruit

• thickened walls of ovary

• seed dispersal

True Fruits

• develop from ovary

Accessory or False fruits

• develop from other parts of flower

Fruit Structure

• Pericarp = all tissue outside of seed coat

• Exocarp: skin/ outer covering

• Mesocarp: middle

• Endocarp: inner layer

Types of Fruit

• True Fruits: develops from ripened ovary of a flower

• Accessory or False Fruits: develops from ovary or other parts of flower

Simple fruits

• develops from a single ovary of a single flower

Berries

• simple fruit where two innermost tissue layers are fleshy

Pepos

• type of berry with hard rind

Hesperidium

• type of berry w/ leathery rind

• interior separated into segments

Drupes

Simple fruit where endocarp forms hard enclosure/pit

Multiple Fruits - Accessory Fruits

• formed as result of fused ovaries & other structures

Aggregate Fruit

• forms from one flower w/ many carpels (female)

Pomes

• accessory fruit formed from receptacle

Achenes

• dry fruit that does not split open

Seed Growth

• Germination - resumption of growth and development after a period of seed dormancy

Plant Growth

• enzymes break down the endosperms starch into sugars

• cellular respiration

• cell division at apical meristem

Asexual Reproduction in Angiosperms

• via mitosis

• offspring genetically identical to each other and parent

Asexual Reproduction in Plants

• Apomixis: asexual repro to produce seeds w/out fertilization

• Self Propagation via

  • stolon

  • tuber

  • plantlets

Plant Life Spans

• senescene: aging

• annuals

• biennials

• perennials

Plant Life Spans - Monocarpic

• flower only once in lifetime and die soon after

Plant Life Spans - Polycarpic

• flower many times