UNIT 6

Chapter 29: Plant Diversity IChapter 30: Plant Diversity II

Chapter 31: FungiChapter 35: Plant Structure & Growth

Types of Land PlantsTypes of Land Plants

Plants are: multicellular, eukaryotic, Plants are: multicellular, eukaryotic, photosynthetic autotrophsphotosynthetic autotrophs

Four MAIN groups of land plants exist:Four MAIN groups of land plants exist:– BryophytesBryophytes: seedless, non-vascular: seedless, non-vascular– PteridophytesPteridophytes: seedless, vascular: seedless, vascular– GymnospermsGymnosperms: seeded, non-flowering: seeded, non-flowering– AngiospermsAngiosperms: seeded, flowering: seeded, flowering

VascularVascular plants possess vessels plants possess vessels (tubes) for transport of water and (tubes) for transport of water and nutrientsnutrients

Features of Land PlantsFeatures of Land Plants

Main characteristics of the four Main characteristics of the four groups of land plants:groups of land plants:– MeristemsMeristems

Regions located at specific places from Regions located at specific places from which new growth occurswhich new growth occurs

– Apical, lateralApical, lateral

– Multicellular embryos dependent on Multicellular embryos dependent on the parent plantthe parent plant

Embryo is retained by parent; provides Embryo is retained by parent; provides nutrientsnutrients

– Alternation of Alternation of generationsgenerations

Two multicellular Two multicellular body forms body forms alternatealternate

– SporophyteSporophyte: : 2n2n, , produces produces nn spores by spores by meiosismeiosis

– GametophyteGametophyte: : nn, come , come together to together to form form 2n2n zygote zygote

– Sporangia that produce sporesSporangia that produce spores Organs on the sporophyte that produce Organs on the sporophyte that produce

sporesspores– MegasporangiaMegasporangia: produce : produce

megaspores, becomes female megaspores, becomes female gametophyte = produces egggametophyte = produces egg

– MicrosporangiaMicrosporangia: produces : produces microspores, becomes male microspores, becomes male gametophyte = produces spermgametophyte = produces sperm

Spores will be released into airSpores will be released into air– Gametangia that produce gametesGametangia that produce gametes

Organs on gametophyte that produce Organs on gametophyte that produce gametesgametes

– ArchegoniumArchegonium: female gametangium : female gametangium produces a single haploid eggproduces a single haploid egg

– AntheridiaAntheridia: male gametangia that produce : male gametangia that produce many haploid spermmany haploid sperm

Other Features of Land Other Features of Land PlantsPlants

Many land plants possess a Many land plants possess a cuticlecuticle, , a waxy layer on leaves to prevent a waxy layer on leaves to prevent water loss and infectionwater loss and infection

StomataStomata, present mostly on the , present mostly on the leaves allow for gas exchange and leaves allow for gas exchange and evaporation of waterevaporation of water

Vascular tissue transports water and Vascular tissue transports water and nutrients (except bryophytes)nutrients (except bryophytes)– XylemXylem: transport of water and : transport of water and

nutrients from rootsnutrients from roots

Xylem is “dead” at maturity – only cell wall Xylem is “dead” at maturity – only cell wall remainsremains

– PhloemPhloem: distribution of sugars, amino : distribution of sugars, amino acids and other organic moleculesacids and other organic molecules

Phloem is living tissuePhloem is living tissue

END

SeedsSeeds

A A seedseed is a sporophyte embryo with is a sporophyte embryo with its own food supply in a protective its own food supply in a protective coatcoat– Seed plants (gymnosperms and Seed plants (gymnosperms and

angiosperms) retain their sporesangiosperms) retain their spores Microspores develop into Microspores develop into pollenpollen

– Carried off by wind or animalsCarried off by wind or animals – Pollen carry sperm (1 or 2) to Pollen carry sperm (1 or 2) to ultimately ultimately pollinatepollinate an egg an egg

Sperm are unflagellatedSperm are unflagellated

GymnospermsGymnosperms

Modern gymnosperms appeared Modern gymnosperms appeared ~350mya~350mya

Gymnosperms reflect 3 Gymnosperms reflect 3 major changes in the major changes in the evolution of plantsevolution of plants– Increasing dominance of Increasing dominance of

the sporophytethe sporophyte– Seeds resistant enough for Seeds resistant enough for

dispersaldispersal– PollenPollen

Conifers are the most common Conifers are the most common group of gymnospermsgroup of gymnosperms– Most have male and female Most have male and female conescones on on

the same plantthe same plant Smaller pollen cones produce microspores Smaller pollen cones produce microspores

which develop into male gametophytes = which develop into male gametophytes = pollenpollen

Larger ovulate cones make megaspores Larger ovulate cones make megaspores that develop into female gametophytesthat develop into female gametophytes

– Seeds typically dispersed by windSeeds typically dispersed by wind

Most conifers are evergreen (vs. Most conifers are evergreen (vs. deciduous) and photosynthesize all deciduous) and photosynthesize all yearyear

Needles are modified leaves Needles are modified leaves adapted to dry conditionsadapted to dry conditions– Most have thick cuticlesMost have thick cuticles

Most lumber and paper comes from Most lumber and paper comes from conifers (xylem tissue)conifers (xylem tissue)

Conifers are among the oldest and Conifers are among the oldest and largest organisms on earthlargest organisms on earth

AngiospermsAngiosperms

Angiosperms have existed for Angiosperms have existed for ~130my~130my– Categorized into two groups: Categorized into two groups: monocotsmonocots

and and dicotsdicots– ~250,000 known species~250,000 known species

TheThe flower flower is the most significant is the most significant evolutionary adaptation found in evolutionary adaptation found in angiospermsangiosperms– Reproductive structureReproductive structure

Animals (esp. insects) often used to Animals (esp. insects) often used to transfer pollen transfer pollen

Angiosperms – The Angiosperms – The FlowerFlower

Flowers are Flowers are modified shoots modified shoots with four types with four types of modified of modified leaves called leaves called whorlswhorls– SepalsSepals, , petalspetals, ,

stamensstamens, , carpelscarpels

Female – carpelFemale – carpel Male – stamenMale – stamen

Angiosperms – The FruitAngiosperms – The Fruit

A A fruitfruit is a mature ovary is a mature ovary– After fertilization, ovary wall thickens After fertilization, ovary wall thickens

to form fruitto form fruit– Protect dormant seeds and aid in Protect dormant seeds and aid in

dispersaldispersal

Various modifications exist to aid in Various modifications exist to aid in dispersaldispersal– Ex. Dandelions and maples use windEx. Dandelions and maples use wind– Many angiosperms use animals for Many angiosperms use animals for

dispersaldispersal Edible fruits eaten and passed unharmed Edible fruits eaten and passed unharmed

(along with fertilizer)(along with fertilizer)

Three Three main fruit main fruit types types existexist

Plants & HumansPlants & Humans

All animals ultimately depend on All animals ultimately depend on plants, either for oxygen or for foodplants, either for oxygen or for food

Angiosperms provide virtually all of Angiosperms provide virtually all of our food (~12 species)our food (~12 species)– Fruits, vegetables, grasses (corn, Fruits, vegetables, grasses (corn,

wheat, rice)wheat, rice) Diversity in plants is a non-Diversity in plants is a non-

renewable resourcerenewable resource– Human growth vs. plantsHuman growth vs. plants

Many plant (and animal) species go Many plant (and animal) species go extinct as forests are cut down for extinct as forests are cut down for agricultureagriculture

Ethical concerns are not the only Ethical concerns are not the only issueissue– Food, building materials, medicinesFood, building materials, medicines

Only about Only about 2% of the 2% of the 250,000 250,000 known plant known plant species have species have been studiedbeen studied– More than More than

25% of 25% of prescription prescription drugs are drugs are isolated from isolated from plantsplants END

Fungi

Fungi are (usually) multicellular, eukaryotic, non-vascular, heterotrophic and possess a cell wall made of chitin Acquire nutrients by secreting exoenzymes

and absorbing nutrients Act as decomposers, mutualistic symbionts

and parasites Mycorrhizae are mutualistic associations

between plant roots and fungi

Fungus increases surface area for absorption by plant roots Fungus provides

minerals from soil to plant; plant provides organic nutrients

Almost all vascular plants have a mycorrhizae Plant growth is

often stunted without mycorrhizae

END

Plant Anatomy

Plants have three basic organs: roots, shoots and leaves

Angiosperms have most features in common, but a few major features distinguish the monocots from the dicots

A basic plant

Plant Tissue Systems

There are three main types of tissues found in plants: ground, dermal and vascular All types are found

throughout the plant Dermal

Covers outer surface of plant

Extends to create root hairs

Secretes cuticle

Vascular (xylem) Tracheids are

individual units of xylem

Vascular (phloem) Organic material

moves through chains of cells called sieve-tube members

Ground Neither dermal nor vascular Photosynthesis, storage and support

The three tissue types are made up of three major cell types Parenchyma: (living) sieve-tube members,

photosynthesis, storage Collenchyma: (living) support young parts

of plant Sclerenchyma: (dead) thick cell walls,

tracheids, support & transport

Growth & Development

Most plants grow and develop throughout their lifetime – indeterminate growth Growth: increase in mass due to cell division Development: changes that elaborate an

organism’s body Plant life cycles vary based on when they are

capable of reproduction Germination flowering seed production

death Annual, biennial, perennial

Meristems are regions of embryonic cells Apical: increase in

plant’s length/height – primary growth

Lateral: increase in plant’s width – secondary growth

Leaf Anatomy

Leaf epidermis comprised of tightly packed cells Stomata: tiny pores found

in the epidermis flanked by guard cells

Water pressure in guard cells control stomata opening/closing

Mesophyll is ground tissue sandwiched in between two epidermal layers

O2 and CO2 circulate in the spaces in the parenchyma

Vascular tissue is continuous with that of the stem

END