GR11 Biology Unit 5: Plants

Photosynthesis

CO₂ + H₂O + energy (on top of arrow!) —> C₆H₁₂O₆ + O₂

Cellular Respiration

• Animals (heterotrophs) eat plants/ animals to obtain the sugar

• We use the oxygen to burn the sugar during cellular respiration to release stored energy (chemical energy)

Basic Needs of Plants

• CO₂: Obtained from the air via leaves

• H₂O: Mostly obtained by roots in the soil

• Carbohydrates (glucose): Made via photosynthesis

• Solar energy: leaves absorb sunlight

• Nutrients (S,C,H,N,O,P): To make proteins, lipids, and other compounds: obtained through roots.

Monocot (angiosperm)

1 cotyledon (seed leaf) when sprouting

Dicot (angiosperm)

2 cotyledons (seed leaves) when sprouting

Characteristics of ALL plants

• Eukaryotic

• Cell walls containing carbohydrate cellulose

• Autotrophs: carry out photosynthesis using pigment chlorophyll (found in chloroplasts) to transform light energy —> chemical energy

4 Plant Tissues

Vascular, Ground, Dermal, Meristematic

Dermal Tissue Function

Protective outermost covering

• Dehydration: epidermal leaf cells produce a waxy substance to prevent water loss (cuticle)

• Defence: some plants have hair like needles for defence

2 types of dermal tissue

• Epidermal tissue: outermost covering of leaves

• Periderm tissue: outer covering of woody plants

Specialized Cell: Dermal Tissue

• Guard cells form a stomata

  • Stomata: Pore for gas exchange on lower leaf surface

• They shrink or swell up in order to open and close the stomata

Ground Tissue Function

• Most of the plant is made of ground tissue (stem, roots, leaves)

• Operates as a filler between D/V tissue

  • Stem: Provides strength, support

  • Roots: stores carbohydrates and water

  • Leaves: where photosynthesis occurs

Specialized Cell: Ground Tissue

Mesophyll cells in leaves are where photosynthesis occurs

Vascular Tissue Function

• Transpiration: moves substances (water) from roots to leaves

• Translocation: Transports sugars from leaves to other parts of plant

• Support plant body

Examples: Vascular Tissue (2)

• Xylem: Dead, elongated cells that move water/minerals upwards from roots to leaves

• Phloem: Live, elongated cells that transport sugar produced during photosynthesis to other parts of the plant for energy

Meristematic Tissue

• Function:

  • Unspecialized tissue capable of dividing by mitosis

  • Responsible for growing new parts of plant

  • Several locations for growth: stem/root tips, leaves

• Specialized Cells: “Stem cells” of plants

4 Plant Organs

Roots, Stem, Leaf, Flowers (angiosperm only)

Roots Function

• Collect and transport water/nutrients absorbed through root hairs (dermal tissue)

• Anchor plant to soil

• Some store water/carbohydrates

2 Types of Roots

• Tap: Large, thick main root which grows straight downward

  • Grows deep into soil

  • In gymnosperms and angiosperms (mostly dicots)

  • Lateral roots: Smaller roots that branch from larger root

• Fibrous: Many small roots that may have lateral roots

  • Shallow compared to taproots

  • In angiosperm monocots

Root Hairs

Most water is absorbed

Cortex

Specialized cells that store starch and transport water from epidermis to xylem (ground tissue)

Endodermis

Moves water/substances from cortex to vascular tissues (ground tissue)

Vascular Cylinder

Central portion of root that contains xylem and phloem

• Gymnosperm and dicots: xylem form an X in the middle, surrounded by phloem

• Monocots: Ring of xylem and phloem cells surround ground tissue (parenchyma)

Root Cap

Thick layer of cells that produce a slippery substance to help root penetrate soil

• Meristem produces new cells to increase root length

Leaf Function

• Gas exchange: Trading O₂ and CO₂

• Photosynthesis: Chemical reaction of CO₂ and H₂O to form sugar and oxygen

  • Absorption of sunlight with chloroplasts which contain chlorophyll

• Defenses: Protection from predators (eg. toxins, cactus spines, surface hairs)

Blade

Flattened area (good surface area for light absorption)

Petiole

Stalk that attaches blade to stem

Simple leaves

1 blade on 1 petiole

Compound leaves

Several leaflets on 1 petiole

Veins

Contains vascular tissue (monocots or eudicots)

Epidermal cells

Single layer above and below the leaf

• Waxy cuticle: Prevents dehydration and provides a physical barrier against bacteria, insects, mold

  • Transparent to allow light to pass through them to the cells within leaves

  • Bottom of leaf contains stomata

Stem Function

• Transports water/nutrients throughout the plant body

• Raise and support leaves (photosynthesis) and flowers (reproduction)

• Defense mechanisms (eg. thorns)

• Some modified stems (eg. cacti) store water, carbohydrates, and do photosynthesis

Structure: Stem (2)

• Herbaceous: stems that do not contain wood: pliable, do photosynthesis, thin epidermis

• Woody: stems that contain wood: hard, bark, do not carry out photosynthesis

  • All gymnosperms are woody

  • Most woody angiosperm are eudicots. Monocots do not produce wood

Contain vascular bundles.

Flower (angiosperm) Function

Key organs in sexual reproduction of angiosperm

Male Reproductive Structure: Flowers

• Stamens: male reproductive part as a whole

  • Anther: produces pollen (contains sperm —> male gamete)

  • Filament: raises anther above female organs

Female Reproductive Structure: Flowers

• Carpel: female reproductive part as a whole

  • Style: stalk that leads to ovary with ovules (contains eggs —> female gametes)

  • Stigma: sticky surface on top of style

2 Types of Pollination

• Cross: pollen grains transferred between different plants

• Self: pollen grains transferred between different flowers on same plant

Leaves: Obtaining Light

• Leaves are flat, wide, have a large surface area to absorb light

  • Palisade layer

  • Spongy Mesophyll

Palisade Layer

Cells near surface of leaf with many chloroplasts: packed tightly together to capture maximum amount of light

Spongy Mesophyll

Contains chloroplasts and space between them to allow gases to move around in the leaf

Leaves: Obtaining CO₂

Gases enter and exit through stomata, controlled by specialized cells called guard cells

Factors that Affect Stomatal Opening and Closing

• Temperature: Heat causes stomata to close due to water loss

• Water in soil: Stomata remains open in order to absorb water

• Time of day (light): Stomata are usually open during the day to perform photosynthesis and gain CO₂

• CO₂ Concentration: Stomata close to prevent water loss and balance photosynthesis

Leaves: Obtaining Water and Nutrients

• Roots gather water/nutrients from soil

• Water travels from the roots to leaves through xylem cells

Hydrogen Bonding

Oxygen from 1 water molecule is attracted to Hydrogen of another water molecule due to polarity/partial charges

Cohesion

Water molecules are attracted to each other

Adhesion

Water molecules are attracted to substances other than itself

Osmosis

Diffusion of water across a semipermeable membrane from low to high solute concentration

Root Pressure

Increasing pressure pushes water up the xylem (not necessarily strong)

Capillary Action

Tendency of a liquid in a narrow tube to rise/fall due to cohesion/adhesion

• Cohesion: Water molecules rise together because they are attached to each other

• Adhesion: Water molecules stick to cell walls of xylem

Transpiration

Evaporation of water through the stomata causes transpirational pull

• Water evaporates and exits leaves via stomata

• As water exits leaves, it pulls on water molecules below, dragging them up from roots to the leaves

• Cohesion: Water molecules come up together

• Adhesion: Fights gravity as water molecules are attached to xylem walls

Translocation

Oxygen and sugar are produced through photosynthesis

• Oxygen: exits through stomata for other organisms to use for cellular respiration (some used by plants as well)

• Sugars: transported from via the phloem

  • stored, used to build carbohydrates, or as a source of energy