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Alternation of generations:
- 1. Haploid gametophyte produces male or female gametes (n) by mitosis.
- 2. Male gamete fertilizes female and they form a zygote which grows into a sporophyte (2n).
- 4. Diploid sporophyte produces spores (n) by meiosis.
- 5. Spore grows into gametophyte (n).
Major plant kingdom divisions:
- Non-Vascular Plants (bryophytes)
- Vascular Plants (tracheophytes)
- - Seedless Plants (pteridophytes)
- - Plants with Seeds (spermatophytes)
- - Naked Seeds (gymnosperms)
- - Enclosed Seeds (angiosperms)
- - Monocotyledons
- - Dicotyledons
- Nonvascular - Embryophytes.
- Rhizoids instead of developed roots.
- Diverse environments such as bog, tundra, exposed rock, and deep shade.
- Help initiate soil-formation and used as fuel.
- Grow flat and close to the ground.
- Rarely more than 30 cells thick.
- Horn-like structures jutting from their base.
Mosses, liverworts, and hornworts are restricted in size because:
They lack a vascular system to move water, nutrients, and sugars.
Seedless Vascular Plants (ferns and reletives)
- Vascular tissue allows them to grow tall (upto 10m).
- Spores dispersed by wind.
- Sporophyte generation is dominant stage while gametophite generation is tiny and short lived.
- Gametes require water to fertilize @sp? because male gametes swim with flagella.
Types of plant vascular tissue:
- Xylem - Dead cells that conduct water and dissolved minerals absorbed by the roots.
- Phloem - Living tube cells and companion cells that conduct sugars produced in the leaves.
Vascular plant parts:
- Roots - penetrate soil to anchor plant and reach water.
- Leaves - provide a large surface area for photosynthesis.
- Stems - rigid tissues that raise and support the leaves.
- Allow sexual reproduction away from water.
- Provide protection against environmental conditions.
- Male - Pollen Cones:
- microspore mother cells undergo meiosis to produce haploid pollen grains.
- Female - Seed Cones
- In each ovule a megaspore mother undergoes meiosis producing one megaspore.
- Pollen traped in sticky sap secreted by female cone fertilize megaspore to form diploid zygote.
- Zygote grows into embryo inside ripened ovule which is now called a seed.
- Naked seeds fall out of cone but may take years to become a mature cone producing plant.
- 1 - Monocot
- 2 - Dicot
- "Vessel Seeds"
- 90% of plant species.
- Fruit and flowers attract animals disperse seeds and carry pollen.
The fertilized ovary of an angiosperm.
How flowers work @Picture@
- In the anther chambers microspore mother cells undergo meiosis to produce haploid pollen grains.
- In the ovule megaspore mother cell undergoes meiosis to produce one megaspore.
- Wind, insects, birst, or bats transfer pollen to sticky surface of the stigma.
- Self-pollination if pollen is from the same plant or cross-pollination if it is from a different plant.
- Fertilized zygote developes into an embryo in the ripened ovule which is now called a seed.
- the ovary and other surrounding parts develope into a fruit enclosing the seed.
- Asexually produces plants with desired characteristics by physically joining different plants so they grow as one.
- Scion: Shoot of grafted plant.
- Root stock: Root of grafted plant.
- Only closely related plants that have a cambium can be grafted.
- The process whereby a community of plants in an area gradually change over time.
- This can be promoted by forest fires and severe storms.
- These changes do not follow a predictable sequence.
- If the plant community becomes stable it is called a climax community.
- Plant communities rarely remain stable for long.
- Only occurs in areas where there was no revious plant community.
- Pioneer spore producing plants such as lichens create soil.
- Moving from this to a forest takes thousands of years.
- Occurs when a plant community is disturbed (by fire, storm, or human activity for example)
- Vascular seed producing plants return without needing pioneer species.
- A forest may develop in as little as 100 years
- Stomata are openings allowing CO2 and H2O vapour to enter plant leaves.
- A stoma is formed between two guard cells.
- Durring the day water enters the guard cells causing them to swell and bend opening the stoma.
- At night water leaves the guard cells and the stoma closes to prevent water loss.
- Outermost layer of leaf.
- Prevents water evaporating.
Leaf Epidermis Tissue
- No photosynthesis.
- Palisade Parenchyma
- - Lots of chloroplasts for photosynthesis
- - Lots of mitochondria for cellular respiration
- Spongy Parenchyma
- - Loosely packed cells.
- - Spaces between cells store H2O vapour, O2, and CO2 for photosynthesis.
Leaf Vascular Bundles
- Made up of xylem and phloem.
- Form veins that deliver water and nutrients throughout leaf.
Leaf Guard Cells
- Found in lower epidermis of leaf.
- Open and close stomata to control flow of gases and vapours in and out of leaf.
Water Movement in Plants
- Water enters plants though root system.
- Water drawn up plant by cohesion and adhesion.
- Cohesion: negative oxygen in one water molecule attracts the positive hydrogen in another.
- Adhesion: water molecules stick to xylem walls.
- Water exits leaves through stomata.
- Light triggers an electron transport mechanism.
- Water is the electron provider for photosysthesis.
- Oxygen is a by-product.
- Carbon dioxide is incorporated into molecules that eventually become sugar.
Glucose in Plants
- Manufactured in the cytoplasm.
- Transported in phloem.
- Used by mitochondria to make ATP (for energy transfer)
- Excess stored as sugar in fruit or as starch in roots.
Equations for Photosynthesis and Cellular Respiration
- 6CO2 + 6H2O + energy → C6H12O6 + 6O2
- Cellular Respiration
- C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
- Bulb (thick fleshy leaf scales)
- - Food storage
- - Onion
- Spines (sharp, woody, non-photosynthetic)
- - Defense, Water Retention
- - Cactus
- Floral Bracts
- - Attracting pollinators
- - Paper flower
- Insect Trap
- - Venus fly trap
- Phylloclade / Cladode (stem that looks and acts as leaf)
- - Photosynthesis
- - Butchers broom.
- Rhizome (thick underground stem grows horizontally)
- - Storage
- - Ginger
- Corm (short swollen vertical stem of several nodes at or below ground)
- - Storage
- - Crocus
- - Climbing and support
- - Grape vine
- Aerial Roots
- - Absorb water from rain or mist
- - Opiphytic orchid
- Pneumatophores (air-breathing roots with air spaces connected to submerged roots)
- - Aeration
- - Mangrove
Plant Epidermal Tissue
- Produces the cuticle which:
- - protects against infection
- - prevents water loss
- - restricts gas exchange.
- In plants with secondary growth epidermis is replaced by periderm (bark).
Plant Ground Tissue
- Parenchyma - Storage and photosynthesis.
- Collenchyma - Flexible support (growing).
- Sclerenchyma - Inflexible tough support (not elongating).
Plant Vascular Tissue
- Cells are dead at maturity.
- - Tracheids - narrow angled end walls.
- - Vessel elements - wider, somtimes lack end walls entirely, only found in angiosperms.
- Transport glucose from leaves to other parts of plant
- - Sieve tube cells - no nuclei, separated by sieve plates.
- - Companion cells - control functions of sieve tube cells.
Vascular Tissue Arrangement
- Stem - vascular bundles scattered through stem. No cambium.
- Stem - vascular bundles in a ring with xylem and phloem seporated by cambium which produces more of both.