SBI3U Plants

Plantae Characteristics

Plantae Characteristics

• Eukaryotic

• Multicellular

• Photosynthetic

• Cell walls contain cellulose

• Sexual or asexual reproduction

• Autotrophic

Vascular and Non-Vascular Plants

• Vascular Plants

  • Have vascular vessels to transport food and water

  • Examples: Flowers and trees

• Non-Vascular Plants

  • Small, simple plants without a vascular system

  • Cannot transport food or water very far

  • Lack roots, have rhizoids

  • Commonly found in moist environments

  • Reproduce sexually by creating single-celled spores or asexually by vegetative propagation

  • Examples: Mosses, liverworts, and hornworts

Plants with Seeds and Seedless Plants

• Plants with Seeds

  • Allow plants to reproduce sexually without needing water and provide protection

  • Appeared about 280 million years ago

  • Divided into 2 groups - Angiosperms and Gymnosperms

• Seedless Plants

  • Do not produce seeds, are dispersed by windblown spores or by water

  • Formed first forests 350 million years ago

  • Examples: Ferns, whisk ferns, club mosses, and horsetails

Angiosperms and Gymnosperms

• Angiosperms

  • Flower producing plants

  • The mature seed is surrounded by an ovule (e.g. apple)

  • Hardwoods

  • Trees have broad leaves that usually change colour and die every autumn

• Gymnosperms

  • AKA naked seeds

  • Non-flower producing plants

  • The seed is not encased by an ovule (e.g. pine cone)

  • Softwoods

  • Usually needles stay green throughout the year

The Seed

3 Primary Parts:

• Embryo

  • The young multicellular organism before it emerges from the seed

• Endosperm

  • A source of stored food (primarily starches)

• Seed Coat

  • Protective layers that encase the seed

Cotyledon

• An embryonic leaf in a seed bearing plant

• The first leaves to appear from a germinating seed

• Single Cotyledon Embryo

  • Monocot, or Monocotyledonous Plant

• 2 Cotyledon Embryo

  • Dicot, or Dicotyledonous Plant

Monocots and Dicots

• Monocots

  • 1 cotyledon

  • Cotyledon is thin, small and lacks food materials

  • Endosperm present and stores food

• Dicots

  • 2 cotyledons

  • Cotyledons are fleshy and store food

  • Endosperm absent

• Key Differences

  • Monocots: 1 cotyledon

  • Dicots: 2 cotyledons

  • Monocots: Energy stored in endosperm

  • Dicots: Food stored in cotyledons

Monocot and Dicot Characteristics

• Monocots

  • Vascular Tissue: Scattered

  • Roots: Fibrous

  • Pollen Grain: 1 Opening

  • Flower Petals: Multiples of 3

  • Cotyledons: 1

  • Leaf Venation: Parallel

• Dicots

  • Vascular Tissue: Arranged in a ring

  • Roots: Taproot

  • Pollen Grain: 3 Openings

  • Flower Petals: Groups of 4 or 5

  • Cotyledons: 2

  • Leaf Venation: Net-like

Word and Chemical Equation of Photosynthesis

• Word Equation

  • water + carbon dioxide + sunlight → glucose + oxygen

• Chemical Equation

  • H2O + CO2 → C6H12O6 + O2

Overview of Photosynthesis

• Occurs in the chloroplast

• Divided into 2 stages

  • Light Reactions

    • Light-Dependent Cycle

  • Calvin Cycle

    • Light-Independent Cycle

    • Dark Cycle

Light Reactions

• Takes place in the thylakoid membrane

• Uses solar energy to:

  • Split water into hydrogen ions, electrons, and oxygen

  • Excite electrons within chlorophyll to set off a series of reactions that create high energy compounds

Calvin Cycle

• Takes place within stroma in chloroplasts

• Uses high energy compounds from light reactions to drive the cycle

• Carbon dioxide combines with intermediate compounds to form glucose

Macromolecules

• Required in large amounts

• Nitrogen (N) - component of proteins, RNA & DNA

• Phosphorous (P) - component of RNA & DNA

• Potassium (K) - controls stomata, water intake

• Calcium (Ca) - development and function of cell walls

• Magnesium (Mg) - component of chlorophyll

Fertilizers

• Two types:

  • Organic: from living sources (e.g. manure, bone meal, and compost)

  • Inorganic: produced chemically

Percent Composition

• 10-10-20

• Refers to the percentage of N, P, and K

• In general:

  • N promotes green growth

  • P promotes root and flower growth

  • K promotes hardiness (e.g. drought resistance)

Micromolecules

• Required in small amounts

• Iron (Fe)

  • Chlorophyll structure and cell respiration

• Zinc (Zn)

  • Regulation of plant growth and function of chloroplasts

• Copper (Cu)

  • Reproduction, root metabolism, and cell respiration

Auxins

• Produced in stem, root tip, and buds

• Promotes elongation (encourages growth)

• Causes the plant to grow tall and straight

• Bends stem towards light (+ phototropism)

• Downward root growth away from light (- phototropism)

• Prevents leaves from falling

Gibberellins

• Promotes seed germination

• Promotes stem and root growth

• Promotes leaf growth

• Promotes flower development

• Increases fruit size

• They are not produced in the stem tip

Cytokinins

• Promotes division and differentiation of cells

• Found in growing areas of plant

• Promotes seed germination

• Promotes flowering

• Prevents aging

Ethylene

• Ripens fruit, prompts leaves to change colour, and petals to die off

• Higher temperatures trigger the production of ethylene

• The gas is able to travel from cell to cell and plant to plant

Abscisic Acid

• Inhibits growth

• Induces dormancy

• Causes leaves to fall

• Involved in opening and closing of stomata as leaves wilt

Tropisms

• Plants also change their growth patterns in response to external stimuli

• Changes in the environment around a plant affect its growth

• These responses are called tropisms and are controlled by hormones

• Positive tropism = growth with/towards stimuli

• Negative tropism = growth away from stimuli

Phototropism

• Stems grow toward light (Positive)

• Roots grow away from light (Negative)

Gravitropism/Geotropism

• Roots grow with gravity (Positive)

• Stems grow against gravity (Negative)

Thigmotropism

Growth in response to touch (e.g. vines)

Stem Structure

• Stems are one of two main structures in vascular plants (the other is the root)

• Stems are made up of nodes and internodes

  • Nodes hold leaves and buds which grow into branches

  • Internodes are the spaces between nodes

Stem Functions

• Support for leaves, flowers, and fruits

• Transport of fluids between the roots and the shoots in the xylem and the phloem

• Storage of nutrients

• Production of new living tissue

• Normal lifespan of plant cells: one-three years

• Meristems generate new living tissue

Stem Tissues

There are 3 main tissues:

• Dermal Tissue

  • Outer surface of stem

  • Used to waterproof, protect, and control gas exchange

• Ground Tissue

  • AKA fundamental tissue

  • Performs photosynthesis

  • Functions as storage and support

• Vascular Tissue

  • Provides long distance transport and structural support

Herbaceous Dicots

• Stems with primary growth

• Pith (ground tissue) in the centre

• Vascular bundles are arranged in a distinct ring around the outside

• Epidermis and cuticle protect the outside of the stem

• Limited height due to weight support

Woody Dicots

• Secondary growth thickens stem

• Vascular cambium cell division

• Secondary xylem (inside) and phloem (outside)

• Cortex and epidermis destroyed

• Cork cambium develops cork cells

• Secondary xylem becomes wood (structural support)

Tree Rings

• Cork cambium stops after growing season

• Growth ring formed

• Spring: More xylem, larger cells, less dense wood

• Fall: Fewer, smaller xylem, dense wood (visible ring)

Monocot Stems

• Vascular bundles scattered (screaming faces)

• Rare secondary growth

• Seldom woody

• Exceptions: Palm trees and bamboos

Cell Types of Vascular Tissue

• Xylem: Tracheids and Vessel Elements

  • Thick walled

  • Dead at maturity

  • Rich in lignin for strength

  • Non-living cells

  • Transport water from roots to leaves

• Phloem: Sieve Tubes and Companion Cells

  • Live at maturity

  • Contain cytoplasm

  • Living cells

  • Transport sugar from leaves to roots

• Xylem and phloem form long, continuous tubes

Plant Structure

• Root System

• Shoot System

  • Stem

  • Leaves

  • Flowers

Root System Functions

1. Anchors

2. Absorption (water and nutrients)

3. Transportation

4. Storage

Specialized Root Growth

• Meristem: new cell growth

• Root cap: cells produce mucus-like substance that lubricates root movement in soil

• Root hairs: Increase the surface area for absorption of water and nutrients

Meristem/Meristematic Cells

• Unspecialized cells that divide and differentiate into specialized tissue

Root Structure

• Epidermis

  • Root hairs increase absorption of water and minerals

• Cortex

  • Transports water and minerals from epidermis to vascular cylinder

  • Storage of food

  • Endodermis is the inner waxy layer

• Vascular Cylinder

  • Xylem transports water and minerals from the roots to the leaves

  • Phloem transports sugars from the leaves to the roots

Root Types

• Fibrous roots (Monocots)

  • Ex. Grasses, wheats

• Taproots (Dicots)

  • Ex. Dandelions, carrots

• Adventitious roots (Monocots and Dicots)

  • Ex. Rice, ivy, strawberries

Root Hairs

• Osmosis: water absorption process

• Root cells: hypertonic to soil

• Passive entry via osmosis

• Thin root cell walls

• Large surface area

• Root depth: soil moisture dependent

• Hypertonic: Higher solute concentration than adjacent solutions

Cross Section of Monocot and Dicot Roots

• Monocots

  • Separate strands of xylem and phloem

• Dicots

  • Xylem is x-shaped

  • Separate strands of phloem

Structure and Function (Leaves)

• Function

  • Photosynthesis

    • Uses carbon dioxide

    • Produces water and glucose

  • Structure

    • Designed to capture maximum light and minimize water loss

Leaf Tissues

The leaf is composed of 3 main tissues

1. Dermal Tissues

2. Vascular Tissues

3. Ground Tissues

Dermal Tissues

• Epidermis: Protective outer layer composed of polygonal cells

• Defends against injuries and foreign organisms

• Secretes waxy substance

• Forms cuticle on leaf’s surface

• Cuticle unique to terrestrial plants

• Aids in water retention

Stomata and Guard Cells

• Lower epidermis of leaf

• Microscopic pores: Stomata

• Stoma: Small Opening

• Pair of specialized cells: Guard Cells

Opening and Closing of Stomata

• Guard cells regulate stomata

• Control gas exchange and transpiration

• High solute: water in, guard cells swell. stomata open (day)

• Low solute: water out, stomata close (night)

• Environmental factors influence behaviour

• Hot, dry weather: guard cells close stomata to reduce evaporation

Vascular Tissues

• Leaf connected to the plant’s vascular structure

• Xylem and phloem in stem, branch for leaf supply

• Veins in leaves consist of xylem and phloem

• Vascular components extend through the mesophyll

• Close proximity for photosynthesis

Ground Tissues

• Ground tissue in mesophyll

• Between the upper and lower endodermal layers

• Predominant cells: parenchyma cells

• Contain chloroplasts for photosynthesis

• Mesophyll layers: palisade parenchyma, spongy parenchyma

Monocot and Dicot leaves

• Monocots

  • Dumbbell-shaped guard cells

  • Parallel veins

  • No mesophyll differentiation

• Dicots

  • Kidney-shaped guard cells

  • Reticulate (branched) veins

  • Differentiated mesophyll: palisade, spongy

Water Transport (Xylem)

• Root hairs perform absorption of minerals

• Active transport is the method of mineral absorption

• Energy is needed for active transport

• Energy is produced by glucose stored in the roots through cellular respiration

• Mineral Transport Sequence: soil water, epidermis, cortex, endodermis, xylem

• Hypertonic condition is created due to active transport

• Water enters passively due to osmosis

• Root pressure propels water and minerals up the xylem

Leaf Pull (Transpiration Pull)

• Evaporation of water “pulls” on adjacent water molecules

• Moves up stem via adhesion and cohesion

Bernoulli’s Principle

• Breeze blowing by creates low pressure

• Water and minerals in root in an area of high pressure

• Movement from high pressure towards low pressure

Food (Sugar) Transport

• Sugars actively transported from leaves into xylem

• Active transport against concentration gradient requires ATP

• Hypertonic condition is set up in the phloem relative to the xylem

• Water rushes into phloem passively via osmosis

• High pressure area created in the phloem relative to the roots

• Phloem sap pushed down and stored in roots

Seed Germination

• Radicle pushes down to form roots

• Hypocotyl pushes up to form stem

• Epicotyl and Cotyledon grow upwards to form leaves

• Seeds require heat and moisture for germination

• Gibberellin hormone is released

  • Starches are broken down into simple sugars to provide energy for growing embryo

• Water absorbed into seeds and seed coat cracks

• Oxygen diffuses into seeds for gas exchange

• Radicle emerges and becomes a root

• Hypocotyl emerges and becomes a stem

• Cotyledons from temporary leaves

• True leaves develop and plant matures

Plant Adaptations

• Desert

• Wetlands

• Fire-prone areas

• Extreme cold

• Nutrient-poor soil

• Shade

Desert

• Condition

  • Very dry and often very hot or very cold

  • A lot of direct sunlight

  • Sandy or rocky soil that is unable to hold much water

• Adaptations

  • Hold water in stems

  • No leaves or small ,seasonal leaves to reduce water loss

  • Photosynthetic green stems

  • Long root systems

  • Short life cycle for swift reproduction

  • Germination is initiated by rainfall

  • Hairy leaves to minimize water loss

  • Leaf orientation adjustments to reduce water loss

  • Spines for animal deterrence

  • Waxy coating on stem/leaves to limit water loss

  • Slow growth rate to conserve energy and water

Wetlands

• Conditions

  • Water currents

  • Unstable surface for anchorage

  • Reduced access to sunlight

• Adaptations

  • Floating leaves with stomata on upper surface

  • Chlorophyll on upper epidermis for photosynthesis

  • Hollow stem for buoyancy and diffusion of gases

  • Floating seeds

Fire-prone areas

• Conditions

  • Acidic Soil

  • Extreme heat

• Adaptations

  • Ashes neutralize acidic soil

  • Extreme heat opens tough seed coats (e.g. Jack Pine)

  • Few competitors

Extreme Cold

• Conditions

  • Short, cool summers and long, severe winters

  • Permanently frozen soil sublayer

  • Poor drainage and slow evaporation

  • Little precipitation

• Adaptations

  • Short, low-growing plants due to nutrient scarcity

  • Plants are dark-coloured to maximize solar heat absorption

  • Plants have hair, grow in clumps, and/or have dish-like flowers to for heat retention

Nutrient-poor Soil

• Carnivorous

  • Capture, kill, and digest insects

  • Acquire N, P, and K

  • Ex. Venus fly trap, pitcher plants

• Parasitic

  • Absorb water, minerals, and sugars from xylem and phloem

  • Ex. mistletoe

Shade

• Early bloom

• Rapid growth

• Have broad, thin leaves to catch more sunlight

• Adapted to make more use of soil nutrients as they get less nutrients from the Sun

Gymnosperms

• Conifers are the most numerous

• Reproductive Structures

  • Pollen Cones (Male)

  • Seed Cones (Female)

• Pollen is dispersed by wind

• Pollen produces sperm when contact is made with seed cone

• Sperm fertilizes the ovules

• Zygotes grow into seeds

Angiosperms

• Reproduce sexually

• Flower contains reproductive structures

• Process of reproduction involves 3 steps:

  1. Pollination and Fertilization

  2. Seed Dispersal

  3. Germination

Structure of Flowers

• Male Floral Structures = Stamen

• Female Floral Structures = Pistil (Carpel)

Structures and Functions

• Sepal

  • Protects the flower until it opens

• Flowers

  • Attract animal pollinators to the flower

Stamen (Male)

• Anther

  • Produces pollen

  • Contains sperm

• Filament

  • Holds the anther above the flower

  • Not present in all flowers

Pistil/Carpel (Female)

• Stigma

  • Where pollen attaches

• Style

  • Holds the stigma above the flower

  • Contains pollen tube which pollen goes down to fertilize eggs

• Ovaries

  • Produce egg inside ovule

  • Ovule becomes a seed

  • Ovary develops into a fruit

• Receptacle

  • Attaches the flower to the pedicel (or stalk)

• Pedicel

  • Lifts flower above leaves for access to pollinators

Pollination

• Pollen released from plants, adapted for egg distribution via multiple methods

  • Wind

  • Water

  • Animals (e.g. insects and birds)

• Algae: unique plant with water-distributed pollen

• Wind-distributed pollen characteristics

  • Winged for assistance in travel

  • Produced in large volumes due to high likelihood of missing target

Why are flowers bright colours and smell sweet?

• Flowers use various methods to attract pollen carriers

  • Bright colours

  • Sweet smells

  • Nectar production

• Colour-specific attractions

  • Bees: Yellow, white, and purple flowers

  • Hummingbirds: Pink, orange, and red flowers

Fertilization

• Pollen uses enzymes to navigate

  • Route: Down pollen tube, through the stigma, to ovules

• Fertilization process

  • Each ovule is fertilized with a sperm from pollen

• Sperm (1N) and egg (1N) fusion

  • Result: Zygote (2N)

• Additional sperm (1N) fuses with a polar nuclei (2N)

  • Result: Endosperm (3N)

• Endosperm function: feed developing zygote

Seed Dispersal

• Wind (e.g. dandelions, maple key0

• Water (e.g. coconut)

• Animals externally (e.g. burdock)

• Animals internally (e.g. ingested fruit seeds)