Plants
General Biology II Lecture
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Land Plants – monophyletic group, “embryophytes”
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Nonvascular
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Hepatophyta – liverworts
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Anthocerophyta – hornworts
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Bryophyte – mosses
Vascular, seedless
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Lycopodiophyta – club mosses
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Monilophyta – horsetails, whisk ferns, ferns
Vascular, seed
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Gymnosperms
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Cycadophyta
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Ginkgophyta
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Gnetophyta
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Coniferophyta
Angiosperms
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Monocot
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Eudicot
Know facts about each group, look at evolutionary history
Life Cycle
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Alternation of Generations
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In nonvascular plants, gametophyte generation is dominant; in vascular plants, sporophyte generation is
dominant
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Nonvascular plants
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Flagellated sperm rely on water source
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Female gametophyte – archegonium, produces egg
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Male gametophyte – antheridium, produces many sperm
Vascular Plants
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Megaspores (produced in SMALL numbers in megasporangia) develop into female megagametophyte
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Micropores (produced in LARGE numbers in microsporangia) develop into microgametophyte (pollen
grain)
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Seed Plants
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Seed – well protected resting stage
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Tissues from 3 generations
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Seed coat and megasporangium from sporophyte parent
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Haploid female gametophyte – nutrients
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Embryo – new diploid sporophyte
Gymnosperms “naked seeds”
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Megastrobilus – female seed-bearing cone; modified stem
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Microstrobilus – male, pollen bearing cone; modified leaf
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Fertilization
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Pollen distributed by wind
2 sperm travel through pollen tube – one fertilizes, other degenerates
Angiosperms
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Double Fertilization
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Microgametophyte has 2 male gametes
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1 fuses with egg
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1 fuses with 2 haploid nuclei of female to make triploid endosperm
Megagametophyte is only 7 cells
Can be monoeicius or dioecius
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Most dioecius plants have methods that prevent self-fertilization
Flower Structure
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Pistil (can be one carpel or several carpels fused together), bear
megasporangium
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Stigma
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Style
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Ovary – develops into fruit
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Ovule – develops into seed
Stamen, bear microsporangia
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Anther
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Filament
Flowers can be perfect or imperfect
3 patterns of flowering:
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Annuals – complete life cycle in 1 year and have little or no secondary growth
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Biennials – take 2 years, store carbs underground during 1st year and then
produce flowers 2nd year
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Perennials – live 3 or more years
Fruits – develop from ovary of carpel
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Simple – develop from one carpel, cherries
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Aggregate – develop from several carpels on same flower, raspberries
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Multiple – develop from cluster of flowers, pinapple
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Accessory – fruits develop from parts other than carpels
Plant Body of Angiosperms
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3 vegetative organs organized into root and shoot systems:
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Stems
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Roots
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Leaves
Root
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Taproot
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Fibrous roots (most of the monocots)
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3 Zones: Zone of maturation, zone of elongation, zone of cell division; root cap
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Monocot vs. eudicot root
Stems
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Support leaves and flowers
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Have buds
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Axillary buds – can form new branches
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Terminal buds – at tips, can form new branches upward, can form flowers
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Can be modified – potatoes, runners on strawberries, barrel on cactus to store water
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Monocot vs. eudicot stem
Leaves
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Consists of blade and petiole that attaches it to stem
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Can be modified – cacti spines, onion
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Root and shoot systems consist of apical meristems at tips (clusters of undifferentiated cells)
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3 tissue types
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1. Dermal
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Forms the epidermis
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2. Ground – makes up most of the plant body
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3 cell types:
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Palisade mesophyll
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Spongy mesophyll
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Collenchyma – provides support
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Sclerenchyma – fibers and schlereids, rigid support
3. Vascular
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Xylem – transports water and nutrients from roots
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Cells called tracheary elements (die before assuming role)
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Water moves through xylem by transpiration-tension-cohesion mechanism
Phloem – transports products of photosynthesis
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Parenchyma – sites for photosynthesis and storage
Cells called sieve tube elements, still living
Primary vs Secondary Growth
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Primary – extension of root and shoots
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Apical meristems
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All monocots, some eudicots
Secondary - increases diameter, production of wood
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Eudicots
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Lateral meristems
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Vascular cambium – provides secondary xylem toward inside of stem and phloem
toward outside of stem
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Cork cambium
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Cork, cork cambium, and phelloderm make up the periderm
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Periderm + Secondary Phloem (everything external to vascular cambium)
becomes bark
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Hormones
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Plant development dependent on hormone regulation
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Gibberellins – stem elongation
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Auxins – phototropism and gravitropism; inhibit abscission (detachment of leaf from stem)
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Effects of ethylene gas