chapters 23-26. all plants… multicellular, eukaryotic, autotrophic
TRANSCRIPT
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PLANTS
Chapters 23-26
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Evolution of PlantsAll Plants…• multicellular, eukaryotic, autotrophic
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Angiosperms
Monocots vs. Dicots• named for the numberof cotyledons present on the embryo of the plant
+ monocots- orchids, corn, lilies, grasses
+ dicots- roses, beans, sunflowers, oaks
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Alternation of GenerationsSporophyte (diploid)• produces haploid spores via meiosis
Gametophyte (haploid)• produce haploidgametes via mitosis
Fertilization• joins two gametes toform a zygote
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Plant MorphologyMorphology (body form)
- shoot system + stems, leaves, flowers- root system + taproot, lateral roots
• vascular tissues + transport materials between roots and shoots
- xylem/phloem
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Plant Anatomy Anatomy (internal structure)• division of labor + cells differ in structure and function
- parenchyma, collenchyma, sclerenchyma (below)
ParenchymaSt: “typical” plant cellsFu: perform most metabolic functions
CollenchymaSt: thick wallsFu: provide support but allow growthin young parts of plants
SclerenchymaSt: hardened secondary walls (LIGNIN)Fu: specialized for support; dead
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Plant cell types• Xylem • Phloem
WATER-CONDUCTING CELLS OF THE XYLEM
Vessel Tracheids
Tracheids and vessels
Vesselelement
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Companion cell
Sieve-tubemember
Sieve-tube members:longitudinal view
Sieveplate
Nucleus
CytoplasmCompanioncell
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Water- and Food-conducting CellsXylem (water)
• dead at functional maturityPhloem (food)• alive at functional maturity• sieve-tube cells- arranged end to end with sieve plates &Companion cells
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Plant TissuesThree Tissue Systems• dermal tissue + epidermis (skin)
- single layer of cells that covers entire body- waxy cuticle/root hairs
• vascular tissue + xylem and phloem
- transport and support• ground tissue + mostly parenchyma
- filler tissue- photosynthesis, storage, support
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Plant GrowthMeristems• embryonic tissues located at regions of growth
- apical meristems (primary growth- length) + located at tips of roots and shoots- lateral meristems (secondary growth- girth)
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Roots• A root
– Anchors the plant– Absorbs minerals and water– Stores organic nutrients– Taproots: vertical– Lateral roots: horizontal branches– Fibrous root system in monocots (e.g. grass)
Figure 35.3
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Modified Roots• Many plants have modified roots
(a) Prop roots (b) Storage roots(c) “Strangling” aerial
roots
(d) Buttress roots (e) Pneumatophores
(a) Prop roots (b) Storage roots
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Modified Stems
Rhizomes(d)
Tubers (c)Bulbs
Stolons
(a)
Storage leaves
Stem
Root Node
Rhizome
Root
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Buds• An axillary bud
– Forms a lateral shoot• A terminal bud
– Causes elongation of a young shoot
Gardening tip:Removing the terminal bud stimulates growth of axillary buds (e.g. makes plants bushier)
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The leafIs the main photosynthetic organ of most vascular plants
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Modified Leaves
Tendrils
Spines
Storage leaves
Bracts
Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.
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Leaf AnatomyEpidermal Tissue• upper/lower epidermis• guard cells (stomata)
Ground Tissue• mesophyll +palisade/spongy parenchyma
Vascular Tissue• veins + xylem and phloem
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The Vascular Cambium and Secondary Vascular Tissue
• The vascular cambium– Is a cylinder of meristematic cells one cell thick– Develops from parenchyma cells
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Secondary Growth
• As a tree or woody shrub ages– The older layers of secondary xylem, the
heartwood, no longer transport water and minerals
• The outer layers, known as sapwood– Still transport materials through the xylem
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PLANT REPRODUCTION
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Plant ReproductionSporophyte (diploid)• produces haploid spores via meiosis
Gametophyte (haploid)• produce haploidgametes via mitosis
Fertilization• joins two gametes toform a zygote
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Double FertilizationDouble Fertilization• pollen grain lands on stigma + pollen tube grows toward ovule + 2 sperm discharged down the tube
- egg and one of the sperm produce zygote
- 2 polar nuclei and sperm cell produce endosperm
+ ovule becomes the seed coat + ovary becomes the fruit
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Seed Structure and Development
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Asexual Reproduction in Plants: Vegetative Propagation
• Budding and Grafting: smaller stems from one plant are attached to another plant• Taking cuttings: pieces
of one plant are used to grow another• Stems can be modified:• Runners: horizontal
stems aboveground• Rhizome: horizontal
stems belowground• Tuber: swollen
underground stem
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Plant nutrition
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Plant NutritionWhat does a plant need to survive?
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Soil Bacteria and Nitrogen Availability• Nitrogen-fixing bacteria convert atmospheric N2
– plants absorb ammonium (NH4+), nitrate (NO3
-)
Atmosphere
N2
Soil
N2 N2
Nitrogen-fixingbacteria
Organicmaterial (humus)
NH3
(ammonia)
NH4+
(ammonium)
H+
(From soil)
NO3–
(nitrate)Nitrifyingbacteria
Denitrifyingbacteria
Root
NH4+
Soil
Atmosphere
Nitrate and nitrogenous
organiccompoundsexported in
xylem toshoot system
Ammonifyingbacteria
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Nutritional AdaptationsSymbiotic Relationships• Mycorrhizae + symbiotic associations of fungi and roots
- mutualistic relationship: fungus receives food from plant and plant receives increased surface area for root absorption
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Unusual nutritional adaptations
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Plant Transport
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MineralsH2O CO2
O2
CO2 O2
H2O Sugar
Light
• A variety of physical processes– Are involved in the different types of transport
Sugars are produced byphotosynthesis in the leaves.
5
Sugars are transported viaphloem to other parts of the plant.6
Through stomata, leaves take in CO2 and expel O2.
4
Transpiration, the loss of waterfrom leaves, pulls xylem sap upward.
3
Water and minerals aretransported upward in the xylem.
2
Roots absorb waterand mineralsfrom the soil.
1 Roots exchange gases with the soil, taking in O2 and discharging CO2 in cellular respiration
7
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• Water and minerals ascend from roots to shoots through the xylem
• Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves
• The transpired water must be replaced by water transported up from the roots
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Control of Transpiration • Water enters guard cells and causes cells to swell, opening
stomata.• Water leaves guard cell and they shrink, closing stomata
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TranslocationIs the transport of organic nutrients in the plant
Phloem sapIs an aqueous solution that is mostly sucroseTravels from a sugar source to a sugar sink
Translocation through Phloem
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A sugar sourceIs a plant organ that is a net producer of sugar, such as mature leaves
A sugar sinkIs an organ that is a net consumer or storer of sugar, such as a tuber or bulb
Sugar Source & Sink
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HOW DO PLANTS RESPOND TO THE ENVIRONMENT?
Write down as many ways you can think of in your lab notebook.
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Tropisms
• Growth toward or away from a stimulus
• Gravitropism (Gravity)• Phototropism (Light)• Thigmotropism (Touch)
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Plant hormones help coordinate growth, development, and responses to stimuli
• Hormones– Are chemical signals that coordinate the different parts of
an organism
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Photoperiod, the relative lengths of night and day+ Is the environmental stimulus plants use most often to detect the time of year and when to flower