Chapter 38 Angiosperm Reproduction

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