Plant Biology Notes

Plant Structures

Benefits of Vascular Tissue

  • Transport: Xylem and phloem facilitate the movement of water and nutrients.
  • Plant Size: Allows for larger plant sizes.
  • Habitat: Enables plants to live in various habitats.
  • Support: Provides support for roots, stems, and leaves.

Xylem vs. Phloem

  • Xylem: Transports water; unidirectional (roots to shoots).
  • Phloem: Transports nutrients (sugars); bidirectional.

Kingdom Plantae

  • Characteristics:
    • Multicellular
    • Eukaryotic
    • Cell walls made of cellulose
    • Autotrophs
    • Sexual or asexual reproduction

Plant Cells

  • Eukaryotic with membrane-bound organelles.
  • Distinguishing Structures:
    • Cell walls composed of cellulose
    • Chloroplasts: Convert solar energy into chemical energy.

Levels of Organization

  • Cells
  • Tissues
  • Organ
  • Organ System
  • Organism

Plant Categories

  • Non-vascular: Lack specialized transport tissues.
  • Vascular: Possess vascular tissues.

Vascular Meaning

  • Relating to vessels for transport.

Non-vascular Plants

  • Lack:
    • True roots
    • True leaves
    • True stems
  • Why: Lack vascular tissue for transport.
  • Size & Habitat:
    • Small in size
    • Moist environments- rely on osmosis
    • Examples include mosses, hornworts, and liverworts.

Vascular Plants

  • Contain vascular tissue for transport.
  • Have:
    • True roots, stems, and leaves
    • Many specialized structures

Plant Tissues

  • Types:
    • Dermal Tissue
    • Ground Tissue
    • Vascular Tissue
    • Meristematic Tissue

Dermal Tissue

  • Epidermis: On non-woody parts.
  • Periderm: Cork/bark on woody parts; made of dead cells.
  • Covers the plant.

Ground Tissue

  • Makes up the inside of plants.
  • Functions:
    • Support
    • Store photosynthetic products
    • Carry out photosynthesis in leaves

Vascular Tissue

  • Moves water, minerals, and nutrients.
  • Types:
    • Xylem: Moves water
    • Phloem: Moves nutrients

Xylem and Phloem Details

  • Xylem: Hollow, waterproof tubes; water moves up via capillary action.
  • Phloem: Tubes that allow sugar and minerals to move down.

Tissue Systems

  • Dermal: Outer covering.
  • Ground: Photosynthesis, storage, and support.
  • Vascular: Conducts water and solutes.

Meristematic Tissue

  • Allows plant to grow up, down, and out; mitosis occurs here.
  • Types:
    • Apical Meristem: Growth at tips of roots and branches (up and down).
    • Vascular Cambium: Outward growth (thickness) in the stem/trunk.

Plant Organs

  • Leaves: traps energy from the sun to make “food”, site of gas exchange (carbon dioxide and oxygen)
  • Roots: anchor the plant, absorb water and nutrients from the soil.
  • Stems: provide structure and support, position the leaves to collect sunlight, contains the reproductive structures
  • Flower: part of the reproductive system

Plant Systems

  • Shoots System: Above ground; stems, leaves, flowers.
  • Roots System: Below ground.
  • Reproductive System: Flowers/cones.

Plant Groups

  • Non-vascular: spores, no seeds. Ex: mosses
  • Vascular: seeds cones or flowers. Ex: conifers, flowering plants

Types of Plants

Four Main Groups

  • Nonvascular plants (Bryophytes)
  • Primitive vascular plants (Ferns/Pteridophytes)
  • Cone bearing plants (Gymnosperms)
  • Fruit bearing plants (Angiosperms)

Nonvascular Plants (Bryophytes)

  • Examples: Mosses, Hornworts, Liverworts
  • Characteristics:
    • No vascular system
    • No true roots, stems, or leaves
    • Rhizoids: thin rootlike structure that anchors plant
    • Live near moisture, small and low to the ground, depend on water for reproduction

Seedless Vascular Plants

  • Examples: Ferns, Club Mosses, Horsetails
  • Characteristics:
    • Vascular systems (xylem and phloem) BUT no seeds
    • Larger and more complex than nonvascular plants
    • Adapted to terrestrial environments: transport materials from roots to shoots, reproductive spores have a thick wall

Gymnosperms

  • Examples: Conifers, Cycads, Ginkgos
  • “gymnos” means “naked” in Greek
  • “sperma” means “seed” in Greek
  • Gymnosperms produce seeds not in a sealed container
  • Characteristics:
    • Produce seeds that provide protection and nutrients to the embryo inside
    • Rely on wind for pollination so sexual reproduction can occur even in dry conditions

Angiosperms

  • Examples: Grasses, Flowering Trees, Venus Fly Traps
  • “angeion” means “case” in Greek
  • “sperma” means “seed” in Greek
  • Angiosperms produce seeds within an enclosed structure called a fruit
  • Characteristics:
    • A fruit is a mature plant ovary where seeds develop
    • Bright colors and scents of flowers promote pollination and fertilization
    • Fruits promote seed dispersal and protection for developing seeds

Transpiration

  • Water vapor lost from leaf pores
  • Water travels up through plant
  • Water absorbed by roots
  • describe how water leaves the plant through stomata
  • understand that transpiration is the process by which water moves through a plant from the roots to the stems into the leaves
  • explain the unique properties of water, including: cohesion, adhesion and capillary action

Plant Needs

  • Water
  • Energy
  • Nutrients (minerals and sugar - Nitrogen, phosphorus, potassium, calcium, magnesium, sulfur)
  • Air (carbon dioxide)

How Plants Get These Things

  • Nonvascular plants: simple and small, no roots or stems. Cells absorb water directly, live in wet environments; stay small
  • Vascular plants evolved transport systems: allows plants grow larger
  • Vascular tissues transport materials: connect roots and shoots, consist of xylem and pholem

Vascular Tissues

  • Xylem: transports water and minerals upward from the roots to the shoots
  • Phloem: transports nutrients (food/sugars) from the leaves where food is made to the rest of the plant

Water Uptake

  • Osmosis: water moves from high to low water concentration; Enters root cells because there is less water in the roots than in the soil

Xylem Function

  • Capillary action: tendency for water to rise within a thin narrow tube due to adhesion and cohesion like a straw

Cohesion

  • Water sticks to water due to hydrogen bonds
  • Each water molecule pulls on the next.

Adhesion

  • Attraction between unlike molecules
  • Water sticks to other substances like xylem walls.

Transpiration

  • Evaporation of water from leaves through stomata, Like sucking on a straw

Stomata

  • Allow water vapor to evaporate, allow gas exchange (CO2 in and O2 out).

Water Loss

  • Plants use 90% of water; remaining lost through transpiration.

Factors Affecting Transpiration Rates

  • Higher in hot, dry environments
  • Broad leaves = higher transpiration rates, Narrow leaves = lower transpiration rates
  • Temperature, Humidity, Air Movement

Adaptations to Prevent Water Loss

  1. Thin, narrow leaves: decreased surface area
  2. Reduced number of stomata: Fewer places from which water can escape
  3. Guard cells: control stoma opening and closing
  4. Cuticle: thick, waxy layer to seal in water
  5. Water Storage: large vacuoles store extra water

Reproduction in Seed Plants (Angiosperms & Gymnosperms)

Flower Parts

  • Describe the process of pollination in angiosperms and gymnosperms
  • Identify the reproductive structures in an angiosperm specimen
  • Compare pollination in angiosperms and gymnosperms
  • Female Parts:
    • Stigma: Receives pollen.
    • Style: Tube between stigma and ovary.
    • Ovary: Contains ovules (egg cells).
  • Male Parts:
    • Anther: Produces pollen.
    • Filament: Holds anther.
  • Other Important Parts
    • Petals: Attract pollinators.
    • Sepals: Protect flower bud

Reproduction

  • After pollination, the fertilized ovule becomes a seed and the ovary ripens into a fruit.

Gymnosperm Reproduction

  • Conifers rely on wind pollination, have separate male and female cones
  • Female cones are large and woody and contain ovule, male cones are small and softer and contain pollen
  • Gymnosperms rely on wind for seed dispersal

Special Topics: Adaptations, Tropisms, & Hormones

Plant Adaptations

  • Evolved for: water storage, light capturing, defense, root support, water capturing, reproduction, attract prey

Water Storage Adaptations

  • Smooth, thick, swollen stems and trunks, thick waxy cuticle on leaves and stems, needle leaves (conserve water)
  • Fruits / vegetables grown underground, Thick swollen roots, Swollen tap root

Light Capturing

  • Large broad leaves, tall heights, Large number of leaves, Aerobic roots which allow plants to live in tall trees

Defensive Adaptations

  • Needles and thorns, Rough thick bark, Tall height
  • Fruits / Vegetables underground
  • Bitter taste, Poisonous, Sour smell, Urushiol: botanical allergen. Ex: Poison Ivy, Oleander, Trumpet vine aka Cow itch vine

Root Support and Water Capturing

  • Tall roots: protect from tides, Long fibrous roots, Long tap roots
  • Walking palm moves position around the forest floor to get light

Reproduction Adaptations

  • Fruits and vegetables are tasty so animals eat them and when the animals excrete the waste the seeds are back on the ground
  • Flowers, attract insects for pollination, Sweet smell, bright colors

Reproduction: Seeds Adaptations for Dispersal

  • Dandelion and maple leaves have structures to help them be carried by the wind
  • Apple, strawberries and pears, have small smooth seeds so they can easily pass through an animals digestive system
  • Sticker grass and burls have surface structures to allow them to attach themselves to animals

Carnivorous Plants

  • Evolved a rancid smell to attract small scavenger animals, digestive juices to dissolve creatures for minerals in deficient soil

Plant Tropisms (Responses)

  • Ways plants respond to their environment’s stimulus: Hydrotropism, Phototropism, Thigmotropism, Gravitropism / Geotropism

Hydrotropism

  • Response to water, roots grow in direction of water, roots invade water lines and sewer pipes

Phototropism

  • Response to light, plants grow in direction of light, plant shoots bend towards light because of auxin hormone
  • Auxin is produced on the dark side of the shoot; elongates plan cell casuing the plant to bend towards the light.

Thigmotropism

  • Response to touch, mimosa trees close their leaves when touched, tendrils wrap around other plants

Gravitropism / Geotropism

  • Responds to gravity
  • Negative Gravitropism: Shoots grow up.
  • Positive Gravitropism: Roots grow down

Phytohormones: Plant Hormones

  • Plants grow, produce fruit, ripen fruit, grow and lose leaves all due to hormones. Produced in shoots or roots.

Major Plant Hormones

  • Auxin, Gibberellin, Zeatin, Cytokinins, Abscisic Acid and Ethylene

Auxin

  • Produced in stems, buds and root tips; causes plant to grow towards light, moves to dark side to elongate cells

Gibberellin

  • Produced in young seedlings, promotes fast growth

Cytokinins

  • Involved in cell division and shoot and root development, regulate axillary bud growth and apical dominance

Abscisic Acid

  • Produced in terminal buds; signals dormancy, triggers scales to grow around leaf buds, promotes hibernation

Ethylene

  • Gaseous hormone, opens flowers, ripens fruit, causes leaf abscission