U10 Plant Notes

Plant Structures

Benefits of Vascular Tissue

• Transport: Xylem and phloem facilitate efficient transport of water, minerals, and nutrients.
• Size: Allows for larger plant size due to effective transport systems.
• Habitat: Enables plants to thrive in diverse habitats.
• Support: Provides the ability to support roots, stems, and leaves.

Xylem vs. Phloem

• Xylem:
  • Materials transported: Water and minerals.
  • Direction of transport: Upward, from roots to shoots.
• Phloem:
  • Materials transported: Nutrients (sugars).
  • Direction of transport: Both directions, from source (leaves) to sink (other parts of the plant).

Kingdom Plantae

• Characteristics of Plants:
  • Multicellular
  • Eukaryotic
  • Cell walls made of cellulose
  • Autotrophs
  • Reproduce sexually or asexually

Plant Cells

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

Levels of Organization

• Plants, like animals, have levels of organization:
  • Cells
  • Tissues
  • Organ
  • Organ System
  • Organism

Categories of Plants

• Plants are divided into two main categories:
  • Non-vascular
  • Vascular

Vascular

• Vascular: "Of, relating to, affecting, or consisting of a vessel or vessels"

Nonvascular Plants

• Lack key structures:
  • No true roots
  • No true leaves
  • No true stems
• Lack vascular tissue, so cannot transport water and nutrients to specialized structures.
• Examples: Mosses, Hornworts, Liverworts

Nonvascular Plants (Continued)

• Must remain small in size.
• Must live in moist environments because they lack roots to transport water from deep in the soil.
• Only parts of the plant that can absorb water through osmosis will be hydrated.

Vascular Plants

• Contain vascular tissue, which conducts materials throughout the plant.
• All vascular plants have true roots, stems, and leaves.
• Many specialized structures.

Plant Tissues

• Plants have 4 different types of tissues:
  • 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.
• Specialized to:
  • Support the plant
  • Store photosynthetic products
  • Carry out photosynthesis in the leaves

Vascular Tissue

• Moves water, dissolved minerals, and nutrients throughout the plant body.
• Types:
  • Xylem: Moves water
  • Phloem: Moves nutrients

Vascular Tissue Details

• Xylem: Hollow, waterproof tubes that allow water to rise up in the plant via capillary action.
• Phloem: Tubes that allow sugar and minerals to move down through the plant.

Meristematic Tissue

• Tissue that allows the plant to grow up, down, and/or out.
• Mitosis occurs here!
• Types:
  • Apical Meristem: Allows growth at the tips of roots and branches (up and down).
  • Vascular Cambium: In the outer layer of the stem/trunk that allows outward growth (thickness).

Plant Organs

• Leaves: Traps energy from the sun for photosynthesis; site of gas exchange (carbon dioxide and oxygen).
• Roots: Anchors plant, absorbs water and nutrients (minerals) from the soil.
• Stems: Provides structure and support, positions leaves to collect sunlight, contains reproductive structures.
• Flower

Plant Systems

• Shoots System: Parts of the plant above ground (stems, leaves, flowers).
• Roots System: Part of the plant below ground.
• Reproductive System: Flowers/ cones.

Four Major Groups of Plants

• Non-vascular: mosses.
• Vascular:
  • Spores, no seeds: ferns
  • Seeds in cones: conifers
  • Seeds in flowers: flowering plants

Diversity of Plants

• Four main groups in the plant kingdom:
  • Nonvascular plants (Bryophytes)
  • Primitive vascular plants (Ferns/Pteridophytes)
  • Cone bearing plants (Gymnosperms)
  • Fruit bearing plants (Angiosperms)

Plant Groups Topics

• I. Nonvascular Plants (Bryophytes)
• II. Seedless Vascular (aka primitive vascular - ferns and their relatives)
• III. Gymnosperms (conifers)
• IV. Angiosperms (flowering plants)

Nonvascular Plants (Bryophytes)

• Examples: Mosses, Hornworts, Liverworts
• Characteristics:
  • Do not have a vascular system of xylem and phloem
  • Do not have true roots, stems, or leaves because they do not have vascular tissue
  • Rhizoids: Thin rootlike structure that anchors the plant in place

Nonvascular Plants (Continued)

• Must live near moisture because of no roots.
• Small and low to the ground because of no stems (and no vascular tissue).
• Depend on water for reproduction.

Seedless Vascular Plants

• Examples: Ferns, Club Mosses, Horsetails
• Characteristics:
  • Non-seed vascular plants have vascular systems (xylem and phloem) BUT they do NOT produce SEEDS

Seedless Vascular (Characteristics Continued)

• Larger and more complex than nonvascular plants
• Adapted to live in terrestrial (land) environments
  • Able to transport materials from roots to shoots
  • Reproductive spores have a thick wall around them to prevent them from drying out

Gymnosperms

• Examples: Conifers, Cycads, Ginkgos
• "gymnos" means "naked" in Greek
• "sperma" means "seed" in Greek
• Gymnosperms are plants that produce seeds that are NOT in a sealed container

Gymnosperms (Characteristics Continued)

• Gymnosperms are very successful plants because of the following 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" still means "seed" in Greek
• So Angiosperms are plants that produce seeds within an enclosed structure called a fruit

Angiosperms (Characteristics Continued)

• A fruit is a mature plant ovary where seeds develop
• Angiosperms are the most successful group of plants because:
  • 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 in transpiration
• Water travels up through the plant
• Water absorbed by roots

Transpiration Learning Objectives

• 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)
• Air (carbon dioxide CO_2)

Nutrients

• Minerals and sugar plants need include:
  • Nitrogen, phosphorus, potassium, calcium, magnesium, sulfur
• Come from the soil and get dissolved in the water absorbed by the plant.

How Plants Get What They Need

• Nonvascular plants were the first to evolve and are very simple and small without roots or stems.
• Cannot transport water, food, or nutrients, so all cells must be able to absorb water directly and make what they need!
• They must live in wet environments and stay small.

Vascular Plants Evolution

• Plants evolved a way to transport water and nutrients and therefore could grow much larger, with cells far away from the water source.
• This transport system (the vascular system) is made up of specialized plant cells, called vascular tissue.

Vascular Tissues

• Vascular tissues transport materials from one part of the plant to another and spans both the roots and shoots systems.
• 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 (roots).

Water Transport

• Osmosis facilitates water movement into the root cells from high to low concentration.
• Capillary Action: The tendency for water to rise within a thin narrow tube due to adhesion and cohesion
  Like a straw.

Water Entry

• Path of Water Entering a Root: The order in which water crosses different root structure can be described as follows:
  * Root Hair
  * Epidermis
  * Cortex
  * Endodermis
  * Pericycle
  * Xylem

Xylem Function

• Once water has entered the xylem, it continues to want to move upward because of osmosis.
• Cohesion: Water sticks to water because of hydrogen bonds.
• Adhesion: The attraction between unlike molecules. In plants, water sticking to other substances, like the walls of the xylem.
• Together, cohesion and adhesion allow water to stick together and stick to the sides of the xylem and thus pull the water UP the xylem which is capillary action.

Transpiration

• Transpiration is the evaporation of water from the leaves of plants.
• Transpiration is like you sucking on a straw!
• The water exits the leaves through openings, or pores, called stomata.

Stomata

• Stomata also allow gases into and out of the plant (CO2 in, O_2 out).
• Stoma (singular) vs. Stomata (multiple)

Water Loss

• On average, plants use 90% of water that enters the through their roots
• What doesn’t get used, is lost through transpiration when the water evaporates from the leaves through the stomata

Transpiration Rates

• Vary from plant to plant.
  • Broad Leaves = Higher rates
  • Narrow Leaves = Lower rates
• Depends upon environmental factors
  *Temperature, Humidity, Air Movement
• Transpiration rates tend to be higher in hot, dry environments.

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: Two specialized cells that surround each stoma and control how “open” or “closed” they are
4. Cuticle: Thick, waxy layer on the outside of plants that helps seal in water
5. Water Storage: The large, central vacuoles of each cell store extra water for dry times!

Seed Plant Reproduction

• Angiosperms & Gymnosperms

Reproduction learning objectives

• Describe the process of pollination in angiosperms and gymnosperms
• Identify the reproductive structures in an angiosperm specimen
• Compare pollination in angiosperms and gymnosperms

Flower Parts

• Stamen: Male part; includes the anther (contains pollen) and filament (holds the anther)
• Petal
• Calyx: All the sepals
• Sepal: Small leaves under the flower
• Carpel (Pistil): Female reproductive organ which includes the stigma (receives the pollen during fertilization), style (a tube on top of the ovary), ovary (contains the female reproductive organ, ovule)
• Peduncle

Female Flower Parts

• Stigma: The place where pollen lands in order for pollination to occur.
• Style: A structure between the stigma and ovary.
• Ovary: Contains the female reproductive cells or ovules.
• Ovule: the egg cell, which will become the seed when it is fertilized

Male Flower Parts

• Anther: Produces the male reproductive cells or the pollen.
• Filament: Holds the anther up.

Other Important Flower Parts

• Petals: Attracts pollinators to the flower.
• Sepals: Small leaves under the flower which protect the flower bud.

Flower Variations

After Pollination

• The fertilized ovule (egg) becomes a seed
• The ovary around it ripens into a fruit.

Gymnosperm Reproduction

• Conifers rely on wind pollination
• They 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 cont.

• Gymnosperms rely on wind for both pollination and seed dispersal.

Plant Special Topics

• Adaptations, Tropisms (responses), Hormones

Plant Adaptations

• Plants have evolved adaptations for a variety of reasons such as:
  • 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 Adaptations

• 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 Poison Ivy, Oleander, Trumpet vine aka Cow itch vine

Root Support and Water Capturing Adaptations

• 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 with fertilizer in a location far from parent plant.
• Flowers, attract insects for pollination.
• Sweet smell, bright colors.

Reproduction Seeds

• Seeds have a variety of adaptations to aid in dispersal.
  • Dandelion and maple 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 such as insects, mice and small birds.
• Digestive juices to dissolve the small creatures and receive much needed minerals when growing in mineral deficient soil (ex: Nitrogen).

Plant Tropisms (Responses)

• Plant tropisms are ways plants respond to their environment’s stimulus.
• There are four major plant tropisms:
  • Hydrotropism = response to water.
  • Phototropism = response to light.
  • Thigmotropism = response to touch.
  • Gravitropism / Geotropism = response to gravity.

Hydrotropism

• Plant roots will grow in the direction of water even if it is not below the plant roots.
• Water in the plants roots is attracted to the water outside of the plant.
• Causes plant roots to invade water lines and sewer pipes.

Phototropism

• Plants grow in the direction of light. Some plants will “follow” or turn to the sun over the course of the day.
• Plant shoots bend and grow towards light because of a hormone called auxin.
• Auxin is produced on the dark side of the shoot and elongates the plant cells causing the plant to bend towards the light.

Thigmotropism

• Plants respond to touch.
• Mimosa trees close their leaves when touched.
• Tendrils wrap around other plants or structures they contact.

Gravitropism / Geotropism

• Plants respond to gravity.
  • Negative Gravitropism: Plant shoots will always grow up to the sky UNLESS light is coming to them from a horizontal angle.
  • Positive Gravitropism: Plant roots will always grow towards the center of the earth UNLESS water is a distraction.

Phytohormones: Plant Hormones

• Plants grow, produce fruit, ripen fruit, grow and lose leaves all due to hormones they produce.
• Some hormones are produced in the shoots, while others in the roots.
• The main plant hormones are: Auxin, Gibberellin, Zeatin, Cytokinins, Abscisic Acid and Ethylene.

Auxin

• Auxin is produced in the stems, buds and root tips.
• Auxin moves the plant towards the light and causes plants to grow up towards light.
• When a plant is receiving light from the side, auxin will move to the dark side of the plant to elongate the plant cells causing the plant to bend towards the light.
• Produced from the spring to summer months.

Gibberellin

• Gibberellin is produced in young seedlings and helps them to undergo the cell cycle quickly to promote fast growth.
• Produced in the spring, and in late start plants.

Cytokinins

• Cytokinins are involved in many plant processes, including cell division and shoot and root development.
• They are known to regulate axillary bud growth and apical dominance.
• Cytokinins work in conjunction with phytohormones such as auxin.

Abscisic Acid

• Abscisic acid is produced in the terminal buds of plants. It signals dormancy.
• Abscisic acid triggers leaf bud to have scales grow around them to protect them through the winter months.
• Abscisic acid promotes the plants hibernation phase.
• Produced in the winter.

Ethylene

• Ethylene is a gaseous hormone produced in the fall and autumn.
• Ethylene is actually always present in trace amounts, it opens flowers and causes them to whither away.
• Ethylene is what ripens fruit and causes leaf abscission.