BIOL1510-Exam 2: Chapters 29-31, 35-39 Plants & Botany

Colonization of the Land Masses (3)

• Occurred ~500mya

• First land plants

• Beginnings of habitats

Charophytes/Charophyceans (3)

• relationship to plants

• habitat

• unique characterisitic

• Plants’ aquatic ancestors

• Live in shallow water at the edges of ponds and lakes

• Have sporopollenin (protective coating to prevent from drying out)

Chlorophyta

clade plants belong to

4 common traits between modern plants and charophyceans

1. Rose shaped protein clusters in cell membrane (produce cellulose)

2. Efficient peroxisomes (digestive organelles)

3. Microstructure of flagellated sperm

4. Phragmoplast formation (plant cell division, includes vesicles and cytoskeleton)

5 derived characteristics unique to land plants

1. Apical meristems

2. Embryophtes

3. Alternation of Generations

4. Walled spores within sporangia

5. Multicellular gametangia

Apical meristems (2)

Localized regions of cell division at the tips of shoots and roots (growth centers)

Allows elongation (growth) to access natural resources

Embryophytes (3)

• Multicellular, dependent embryos

• Develop from diploid zygotes and are retained within the parent tissues

• Specialized placental transfer cells to enhance transfer of nutrients from parent (analogous to placenta)

Alternation of Generations (2)

Analogous to that of algal groups (not in charophyceans)

Alternate between multicellular haploid stage (gameteophyte) and a multicellular diploid stage (sporophyte)

Alternation of Generations Process (9)

1. Sporophyte (multicell 2n): Tree

2. Meiosis

3. Spores (unicell n)

4. Mitosis

5. Gametophyte (multicell n): specialized cells

6. Mitosis

7. Gametes (n)

8. Fertilization

9. Zygote (2n)

Walled spores within Sporangia (2)

Spore cells contain sporopollenin (prevent drying) in cell wall

Spores produced in multicellular organs known as sporangia

Multicellular Gametangia

Gametangia: gametes produced in multicell organs

Lost in advanced seed plants

Female: archegonia (1 egg)

Male: antheridia (many sperm: 100s-1,000s)

Water conservation adaptations (2)

• Epidermis coated with cuticle (waxy covering)

  • Also prevents microbial attack

• Stomata

  • Pores that open and close to control water content and gas exchange

Water transport adaptation

• Vascular tissue

• Xylem (water) and Phloem (org. nutrients)

• Analogous to circulatory system

Adaptive structures (3)

True leaves: photosynthesis centers

Stems: support leaves (can contribute to photosynthesis)

Roots: developed to obtain water and anchor plant

Adaptive Production of Secondary Compounds (5)

• definition

• characterisitics

• deter _______ _____ attack

• 2 examples

• Unique compounds produced by plants

• Bitter tastes, strong odors or toxic effects which defend plant from herbivores (insects)

  • Alkaloids, terpenes, and tanins

• Some deter pathogenic microbial attack

• Phenolics (flavinoids): absorb UV to prevent gene damage

• Lignin: hardens cell walls of woody tissues and provides structural support for large plants/trees

Adaptive pollen (2)

Sperm are packaged as pollen

Delivered by wind or animals (water not required)

Non-Vascular Plants

• Lack specialized vascular tissues-no true roots, stems or leaves

• Must remain small and close to water (rely on diffusion)

• Herbaceous (similar to food herbs)-nonwoody, no lignin

• Thin bodies (1-3 cells thick)

• Rhizoids: differ from true vascular roots, not involved in absorption, not composed of tissues, a strand of single cells

Nonvascular Plant Reproduction

Minuscule sporophyte depends on the dominant gametophyte

Phylum Hepatophyta (Liverworts)

nonvascular

Phylum Anthocerophytra

nonvascular

no true leaves

have thallus not roots

Phylum Bryophyta (Mosses)

most common moss

sporophytes contain spores then burst

need wet place

Phylum Bryophyta (mosses) Life Cycle (9)

1. Sporangium (forms spores)

2. Spores (n)

3. Male: Grow and become male gametophyte -rain→ antherida → sperm (n)

4. Female: Grow and become female gametophyte -rain→ archegonia → egg (n)

5. Fertilization within archegonium(2n)

6. Zygote

7. Embryo

8. Young sporophyte

9. Spore capsules grow out of gametophytes

2 Types of Vascular Tissue

1. Xylem: Cell walls of dead cells act as pipes to transport water and minerals from roots

2. Pholem: Living tissue that transports nutrients and organic products from leaves to the rest of the plant

3 Variations of Alternation of Generation in Plants

1. Nonvascular plants: Sporophyte dependent on gametophyte

2. Ferns: Large sporophyte and small, independent (separate) gametophyte

3. Seed plants: Reduced gametophyte dependent on sporophyte

Reasons plants developed dominant sporophyte generation

Genetic variety maintained (2 alleles dominant/recessive traits)

Protects gametophyte from mutations from UV rays

Seedless Vascular Plants

• spore type

• phylums

Homosporous (1 spore type develops into bisexual gametophyte)

2 Phylums

1. Phylum Lycophyta (ancestral)

2. Phylum Pterophyta (derived)

Phylum Lycophyta (2)

• Oldest land plants

• Microphyll: small leaves with only 1 unbranched vein (no expanded flat foliage)

Phylum Pterophyta (3 kinds)

Whisk ferns, Horsetails, and ferns

Whisk ferns (3)

• Phylum Pterophyta

• Lack true leaves and roots

• Anchored to substrate by a rhizome (modified horizontal stem w/ branching rhizoids)

Horsetails (3)

• Marshes and along streams

• Rhizome, true roots, small leaves

• Stems penetrated with large air canals for oxygen movement (grow in low oxygen soils)

Ferns (4)

• diversity

• spore organ

• leaf type

• reproduction

• most widespread and diverse

• Sori: clusters of sporangia w/ spores (n) under fronds

• Megaphylls: true leaves w/ foliage (first w/ leaves)

• Independent gametophyte stage

Fern Life Cycle (Alternation of Generations)

1. Spore (n)

2. Young gametophyte (n)

3. Homospores

   1. Male Antheridium

   2. Female Archegonium

4. Sperm (n) and Egg (n)

5. Fertilization→Zygote (2n) inside archegonium

6. New sporophyte (2n)

7. Mature sporophyte (2n) w/ sori

8. Sori produce spores through meiosis

9. Sporangium (2n)

Reproductive adaptations of seed plants (4)

• Gametophytes reduced and dependent on sporophyte

• Seed replaces the spore as dispersal mechanism

• Pollen used for dispersal of sperm

• Ovule used to house the female gametophyte

Advantages of reduced gametophytes

Since they’re microscopic and develop within the walls of spores with parent tissue they protect the developing gametophyte from environmental stress and enable it to obtain nutrients from the sporophyte

Ovule

consists of megasporangium, megaspore, and at least 1 protective integument

unfertilized reproductive structure

Microsporangium

Male reproductive structure (produces haploid microspores via meiosis)

Consists of male gametophyte enclosed within pollen wall

Can be dispersed great distances by air or animals

Microspores

develop into haploid gametophytes (pollen grain)

Pollination Steps (2)

1. Transfer of pollen to the part of a seed plant containing the ovules

2. A germinated pollen grain produces a pollen tube that discharges sperm into the female gametophyte within the ovule

Most seedless plants are _____

homosporous (single spore produces both male and female gametophytes)

All seed plants are ______

heterosporous (two different spores, each one produces a single type of gametophyte: megasporangium and microsporangium)

Integuments

protective layers of parent sporophyte

Megasporangium

female reproductive structure; produces haploid megaspore via meiosis

Megaspore

divides via mitosis to produce gametophyte

Gametophyte

consists of nutritive material and egg

Seed (4)

• resistant structure that is multicellular and complex in contrast to a spore

• consists of a sporophyte embryo packaged with food supply in protective coating

• can remain dormant until conditions are favorable enough for germination

• can be transported long distances by wind or animals

2 Clades of Seed Plants

1. Gymnosperms (naked seed)

2. Angiosperms (fruit)

Gymnosperms (5)

• first appearance in fossil record

• era of dominance

• food for:

• first evidence of pollination

• site of development

• appear in the fossil record about 305 million years ago because conditions became drier

• dominated terrestrial ecosystems during Mesozoic era

• served as food for herbivorous dinosaurs

• pollinated by insects over 100 million years ago

• develop on the surfaces of specialized leaves known as sporophylls

Ovulate cone

Scale like sporophyll

Site of gametophyte development (ovule)

Female

Staminate cone

Scale like sporophyll

Contain microsporangia

Male

Gymnosperm phyla

1. Cycadophyta

2. Ginkgophyta

3. Gnetophyta

4. Coniferophyta

Cycadophyta (4)

• large cones and palm-like leaves

• flagellated sperm

• thrived during mesozoic period

• ex: coontie (Fl native, mutual w/ atala butterfly)

Ginkgophyta

flagellated sperm

high tolerance to air pollution

Ginkgo biloba: only extant (remaining) species

Gnetophyta

dry, arid habitat

Welwitschia: largest plant leaves (2m)

Other species: Gnetum and Ephedra

Coniferophyta

largest of the gymnosperm phyla

mostly woody cones, some fleshy

mostly evergreens and can carry out photosynthesis all year round

Pinecones: Male vs Female Locality

Female: grow in upper branches, fertilized by pollen blown on the wind from male cones

Male: grow in lower branches

World famous trees

Giant Sequoia: bulk, largest tree

Tule Cypress: largest diameter

Coast redwood: taller than giant sequoia

Conifer life cycle

1. Mature sporophyte

   1. Pollen cone: meiosis→ microsporangium→ pollen grains

   2. Ovulate cone

2. Pollen enters ovule w/ megaspore mother cell

3. Meiosis→surviving megaspore

4. Archegonium

Gymnosperm to angiosperm dominance

Gymnosperms used to be dominant, now angiosperms dominate most terrestrial ecosystems

Gymnosperms still important part of earth’s flora (northern latitudes)

Angiosperms

“container seed”

1 Phylum: Anthophyta

2 key adaptations: flowers & fruits

Flower: reproductive structure of angiosperm

Sepals

green leaves that enclose the flower before it opens (bud)

Petals

colorful leaves that aid in attracting pollinators

Stamens

male

Filament: stalk

Anther: produces pollen on end of filament

Carpels

female

Ovary

Style: stalk

Stigma: receives pollen w/ liquid that traps it

Monoecious

“one house”

Staminate and carpellate flowers are located on the same individual plant

Ex: corn

Dioecious

“two houses”

Staminate flowers and carpellate flowers on separate plants

Ex: date palms, papaya

Coevolution

one species has a direct effect on another closely dependent species

usually relationship is so close one cannot survive without the other

Ex: hummingbirds, Dune primrose (flower with long stem and nectar at the bottom, nocturnal pollinator)

Bee pollinators

attracted to sweet fragrances, UV reflections

Beetle pollinators

attracted to white/dull flowers

strong yeasty, spicy, or fruity odors

Fly pollinators

attracted to dull red or brown, rotten meat odor

Butterfly/Moth pollinators

attracted to sweet fragrances

Hummingbird pollinators

attracted to bright colors, poor sense of smell (primarily visual)

Other plant/insect symbiosis

Orchids mimicking wasp species

Monarch butterflies and milkweed (milkweed has toxins that butterflies use to protect against predators)

Aposematic coloration

brightly colored indicating toxicity

Fruit

Ovary develops into fruit which aids in dispersal of seeds by insects, birds, and mammals

Mature fertilized ovary

Fruit seed dispersal (4)

Mechanisms that disperse seeds by explosive action

Wings (ex: maple)

Seeds within berries and other fruits

Barbs (attach to fur)

2 Major groups of angiosperms & examples

Based on # of cotyledons

Monocots: 1 cotyledon (lilies, orchids, grasses)

Eudicots: 2 cotyledon (peas, sunflowers, oaks)

Monocot characteristics (6)

1. One cotyledon

2. Parallel veins

3. Scattered vascular tissue

4. Fibrous root system (no main root)

5. Pollen grain with one opening

6. Petals in multiples of 3

Eudicot characteristics (6)

Two cotyledons

Netlike veins

Vascular tissue arranged in ring

Taproot (main root) usually present

Pollen grain with 3 openings

Petals in multiples of 4 or 5

Terrestrial adaptations of angiosperms

• Refinement of vascular tissue

• Tracheids: used for both water transport and support in gymnosperms evolved into:

  • vessel elements (xylem cells) for conducting water

  • fiber cells for support

Vessel elements

connect end to end to form continuous tubes

Fiber cells

thick lignified cell walls

Angiosperm life cycle

1. Anther w/ pollen (2n)

2. Meiosis

3. Microspore (n)

4. Mitosis

5. Pollen grain (n)

6. Ovary→meiosis→megaspore

7. Pollination brings gametophytes together in ovary (2 sperm)

8. Sperm fertilizes and develops zygote into sporophyte embryo that is packaged with food into seeds

9. Sperm fuses w/ 2 female nuclei (2n) to form endosperm (3n-triploid); unique to angiosperms

10. Seed

11. Germination

12. Mature flower on sporophyte plant

Plant importance

Agriculture is based almost entirely on angiosperms

Decrease CO2 levels

2 Main Systems of Plants

1. Root system

2. Shoot system (leaves and stems)

Root system

Anchor, store food, absorb minerals and water

Most absorption of water and minerals occur near root tips (have root hairs that increase surface area

Adventitious root

atypical location

used mainly for additional support

ex: ficus tree (on campus), philodendron

Stem structures

Nodes: leaf attachment points

Internodes: segments between the nodes

Axillary bud: located where the base of leaf and stem meet, grows vegetative branch

Terminal bud: found on upper tip of stem, shoot growth and leaf formation

Modified shoots (4 kinds)

• NOT roots

• Stolons: horizontal stems near surface for quick asexual colonization of an area (ex: strawberries)

• Rhizome: horizontal stems growing underground (ex: ginger)

• Tubers: swollen ends of rhizomes for food storage (ex: potatoes)

• Bulbs: vertical underground shoots, stem surrounded by scale-like leaves (ex: onions)

Leaf types and purposes(5)

• Main photosynthetic organ

• Tendrils (pea plant): vine-like for support

• Cacti spines: protection

• Succulent leaves: water storage

• Brightly colored leaves: attract pollinators

• Kalanchoe leaves": Vegetative propagation (asexual reproduction)

3 Plant Tissue Types

1. Dermal (Epidermis): layer of compact cells for protection from microbes and water retention, secrete waxy coating (cuticle)

2. Vascular: transport of materials, Xylem and Phloem in vascular bundles (stem) and vascular cylinder (roots)

3. Ground: all other tissue; pith: internal to vascular; cortex: external to vascular, variety of cell types and multiple functions

Parenchyma cells (6)

• Type of ground tissue

• Synthesis and storage of nutrients

• Chloroplasts in parenchyma cells do photosynthesis

• Least specialized (except phloem)

• All cells start as parenchyma cells and then specialize

• Analogous to stem cells

Collenchyma cells (4)

• Type of ground tissue

• Thick cell walls for support

• Grouped in strands (ex: celery)

• No lignin (non-woody), does not limit growth

Sclerenchyma cells (5)

• Type of ground tissue

• Lignified, woody cell walls

• Dead at functional maturity, supportive

• In areas of plant that’ve stopped growing

• 2 Types: Fibers (hemp) and Sclereids (nutshells, seed coat)

Meristems (2)

• Areas of embryonic tissues that produce new areas of growth

• Primary & secondary growth

Primary Growth (3)

• Elongation (height) of a plant

• Caused by apical meristems at the tips of roots and shoots

• Only type of growth in herbaceous plants (herbs, flowering plants)

Secondary Growth (2)

• Thickening (width) of roots and stems in woody plants (trees)

• Caused by lateral meristems (cork cambium & vascular cambium)

Cork cambium (4)

• Replace epidermis with secondary dermal tissue (bark)

• Produces cork cells which contain suberin (waxy material)

• Layer of cork + cork cambium= periderm

• All phloem layers + periderm= bark

Vascular cambium (3)

• function

• what does wood consist of

  • 2 types

• produces xylem tissue (wood) to its interior and phloem tissue to its exterior

• wood consists of tracheids and fiber cells or vessel elements (angiosperms)

  • Heartwood and sapwood

Heartwood

centrally located tissue to support plant

no water, structural

Sapwood

• peripheral tissue for transprt (xylem)

• used for paper