Chapter 17- Plants, Fungus and the Colonization of Land

• Mycorrhiza- fungus root– Roots of plants covered with fungus growth-

increases absorption of water from soil

• Plants- multicellular photosynthetic eukaryotes• Plant Evolution

– Non-vascular plants- Bryophytes – no vascular tissue, simplest • Ex: algae, moss

– Vascular Plants or Seed Plants- evolved transport system with specialized vascular tissue for land life• Vascular tissues: xylem- brings water and

minerals up; phloem- distributes sugars up and down as needed

• Cuticle and stomata evolved for land life• Most have roots, stems and leaves• Reproduction

– Make sperm and egg (gametes) in gametangia= protective covering of cells for land based reproduction

– Embryophytes- multicellular, embryo nourished by parent- separates plants from algae

• Spores or seeds- adapted for land survival

• 2 types of seed plants: Gymnosperms and Angiosperms– Gymnosperms- do not form flowers

• Seeds develop on surface “naked”- not in a fruit• Cone-bearing plants – make ovules and pollen

grains• Ex: pine, fir, spruce

– Angiosperms- forms flowers- make pollen and eggs• Seeds develop in a protective chamber• Very diverse (250.000 species)

• Flower structure– Specially adapted for process of sexual reproduction– Most contain both male and female reproductive

organs– Stamen-male part

• Anther- makes pollen grains (male gamete)• Filament- holds anther in proper position

– Pistil- female part• Stigma- sticky area that can receive pollen• Style- holds stigma in proper position• Ovary- makes eggs, can develop into fruit

– Accessory organs- petals and sepals– Reproduction involves: meiosis and fertilization

• Pollination– Actual transfer of pollen from anther to stigma– Self-pollination- in same plant– Cross-pollination- between 2 different plants– Pollen vectors- (agents of pollination)- wind, water,

insects, animals

• Germination of pollen– After pollination the pollen grain germinates (sprouts)– Growth of pollen grain and formation of pollen tube– Pollen tube allows sperm to travel to egg

• Fertilization– Pollen tube reaches ovule and releases sperm nuclei

• Fruits and seeds– Ovary develops into fruit– Each ovule develops into seed– Parts of seeds:

• Embyro- developed zygote, grows into seedling• Seed coat- protects embryo• Cotyledon and/or endosperm- stored food for

embryo– Monocot- 1 cotyledon– Dicot- 2 cotyledon

• Seed dispersal– Eaten by animals and pass through system– Wind, water, hooks/barbs, pressure, fire

• Seed dormancy- dormant stage until environment conditions are right, then seed grows and develops

• Seed germination conditions- proper temperature, amount of oxygen, water level

• Mosses and ferns- alternation of generations• 290-360 mil years ago- seedless plants formed vast

coal beds of today = fossil fuels• Expanding human pop threatens diversity

– People pushing into forests- recently destruction is increasing faster

– Many medicines are produced from plants– Goal: encourage sustainable forest management

• Fungi– Plants moved to land w/ mycorrhizal fungi– Fungi- heterotrophic eukaryotes that digest food

externally and absorb nutrients– Reproduce by spores– Lichen- association of algae and fungus, fungus gets

home in exchange for housing, water, minerals– Parasitic fungus accounts for agricultural losses– Many are helpful- mushrooms, antibiotics, truffles