Angiosperm Reproduction

Chapter 38

Angiosperm Reproduction

Angiosperms have 3 unique features: Flowers, Fruits, & Double Fertilization

Microsporangia Pollen sacs in the anther Diploid cells = meiosis male gametophyte

(pollen) Pollen has 2 haploid nuclei

Tube nucleus – 1 sperm develops into a pollen tube

Generative nucleus – divides into 2 sperm cells which remain inside the pollen tube

Ovary

Ovules form with a diploid cell Soon 4 haploid megapsores form Eventually get 8 haploid nuclei, but only

3 are most important 1 haploid nucleus = egg

Will combine with sperm nucleus to form the zygote

2 other nuclei are called polar nuclei Polar nuclei will fuse with sperm nucleus to

make 3n endosperm

Watch Animation

38-01.swf

Pollination

Pollen lands on stigma

Pollen tube made from pollen grain

Pollen tube grows down into the ovary

When pollen tube reaches ovule, double fertilization occurs

Double Fertilization

Double fertilization is the union of 2 sperm cells forming zygote & endosperm

Unique to angiosperms 1 sperm fertilizes the egg zygote

Zygote develops into the embryo sporophyte Other sperm combines with both polar

nuclei = 3n nucleus This 3n tissue endosperm Endosperm – food storing tissue in the seed

After double fertilization

Ovule develops into a seed Ovary develops into fruit which encloses

the seed Fruit protects the enclosed seed Fruit aids in dispersal by wind or animales

Seed coat – protects embryo & its food supply

Radicle – embryonic root Epicotyl – shoot tip with pair of miniature

leaves

Seed

As the seed matures, It goes dormant Low metabolic rate, growth and development

are suspended

Seed resumes growth given suitable environmental conditions for germination

Asexual Reproduction in Plants Asexual reproduction in plants is called

vegetative reproduction Fragmentation

Type of vegetative reproductive When a part of the parent plant is

separated and then generates into a new plant, genetically identical to parent plant

Self-fertilization is another means of asexual reproduction