Plant Organ Systems and Tissues

Plant Organ Systems

• The shoot system supports the plant for photosynthesis and reproduction.
  • It is composed of vegetative parts like leaves and stems.
  • The reproductive parts include flowers and fruits.
• The root system anchors the plant, absorbing water and nutrients.
  • It supports the plant and absorbs water and minerals from underground.

Plant Tissues

• Dermal tissue offers protection and prevents water loss
  • Leaves and stems use it for gas exchange
  • Roots use it for water and ion uptake
• Ground tissues are responsible for metabolism, storage, and support
  • Leaf mesophyll synthesizes sugars during photosynthesis.
  • Stem pith/cortex supports cells
  • Root cortex stores energy carbohydrates.
• Vascular tissues transport fluids
  • Xylem carries water/ions from roots to stems and leaves
  • Phloem carries dissolved sugars from leaves to the rest of the plant

Stomata

• Stomata open to allow gas exchange, carbon dioxide in and oxygen out
• Transpiration also occurs through the stomata

Ground Tissues

• Parenchyma cells are cube-shaped, loosely packed, and thin-walled.
  • Parenchyma contains chloroplasts and are involved in photosynthesis, cellular respiration, and storage.
• Collenchyma cells are elongated, uneven, and thick-walled.
  • Collenchyma cells provide support and wind resistance.
• Sclerenchyma cells have thick, double-celled walls containing lignin.
  • Sclerenchyma cells provide support and strength to the plant.

Vascular Tissue Arrangement

• Monocots have scattered vascular tissue
• Dicots have vascular tissue arranged in a ring

Stem Structures

• Nodes are points of attachment for leaves, aerial roots, and flowers.
• Internodes are the regions between two nodes.
• Petioles are stalks extending from the stem to the leaf base.
• Axillary buds, found in the axil between a leaf and stem, give rise to branches or flowers.
• Apical buds are at the tip of the shoot and contain the apical meristem.

Root Types

• Taproots are single, deep roots found in dicots.
• Fibrous roots are bunches of thin roots found in monocots.

Root Cross-Section

• The epidermis is the outer protective layer, absorbing water and nutrients.
• Xylem transports water from roots to leaves.
• Phloem transports sugars and proteins throughout the plant.
• Root hairs increase the surface area for water and nutrient absorption.

Root Vascular Bundles

• Dicots have an X-shape in the center of the root.
• Monocots have a ring shape around the central pith.

Root Zones

• Maturation zone features a vascular cylinder and root hair formation.
• Elongation zone is where cells stretch.
• Cell division zone is where the apical meristem and root cap are located.

Root Modifications

• Aerial roots extend to the ground to support the plant.
• Aboveground roots support plants in sandy soils.

Leaf Parts

• Lamina is the leaf blade, the widest part of the leaf.
• Petiole joins the leaf blade to the stem.
• Veins, including main central and side veins, transport water and nutrients.
• Midrib is the central vein that provides additional support.
• Stomata allow for gas exchange.

Leaf Structures

• Epidermis is the top and bottom layer of the leaf, one cell layer thick.
• Palisade mesophyll is the upper layer of cells just below the upper epidermis.
• Spongy mesophyll is the lower layer of cells.
• Stomata facilitate gas exchange.

Carnivorous Plants

• Carnivorous plants trap and digest insects using bacteria.
• Digestion yields smaller molecules that the plant absorbs

Plant Needs

• Plants require water
• Plants require sunlight
• Plants require carbon dioxide
• Plants require essential inorganic nutrients and minerals

Macronutrients vs. Micronutrients

• Macronutrients are needed in large quantities, including carbon, hydrogen, phosphorus, potassium, nitrogen, sulfur, calcium, and magnesium.
• Micronutrients are needed in small quantities, like iron, boron, manganese, copper, zinc, chlorine, and molybdenum.
• Nutrients are essential if plants cannot produce them and must obtain them from the environment

Soil Layer

• Humus (topsoil) is the most important layer for plant growth.
  • Humus contains high water levels.
  • It is rich in nutrients from decomposing materials.

Mineral Absorption

• Minerals are absorbed into the roots using ATP.
• Root nodules form relationships with bacteria for nitrogen fixation.
• Mycorrhizae increase the area for mineral absorption, establishing interactions between fungi and plant roots.

Xylem Vessels

• Tracheids are tapered and allow water to pass from one to the next.
• Vessel elements are long and tubular with plates and assemble end to end, like a pipeline.

Water Potential

• Water potential is the mechanical energy of water that moves from one area to another.
  • Water movement depends on osmosis, gravity, pressure, and surface tension.
• Water always from areas of high water potential to areas of low water potential.

Water Movement

• Water moves into roots via osmosis, from areas of higher concentration to lower concentration.
• Water potential determines the direction of water movement.

Root Pressure

• Root pressure is created as water enters the root, adding pressure and pushing existing water upward.

Water Transport

• Cohesion is the ability of water molecules to stick to each other.
• Adhesion is the ability of water to stick to other polar molecules.
• Together, cohesion and adhesion allow water to stick to xylem vessel sides and be pulled upwards against gravity.

Phloem Parts

• Sieve-tube members are alive cells, their end walls have plates with pores and are connected with cytoplasm but have no nuclei.
• Companion cells located next to the sieve tube are alive, have nuclei, and provide proteins to the sieve tube.

Pressure-Flow Model

• Sucrose is transported from source cells to companion cells to sieve tubes.
• As a result, water potential decreases, causing water to enter the phloem from the xylem.
• Water entry leads to positive pressure, which forces the sucrose-water mixture downward toward the roots.
• Transpiration causes water to return to the leaves through the xylem vessels.

Plant Responses to Light

• Photomorphogenesis allows plants to optimize their use of light and space
• Photoperiodism allows plants to track the time of day by sensing and using wavelengths from the sun
• Phototropism allows plants to grow toward or away from sources of light

Plant Defense

• Plants protect themselves from herbivores with an intact, impenetrable barrier
• Bark and waxy cuticles
• Thorns
• Spines

Alternation of Generations

• Plants cycle through sporophyte and gametophyte generations.
• Haploid gametophytes produce male and female gametes via mitosis within multicellular structures.
• Fusion of gametes forms a diploid zygote that develops into the sporophyte
• Diploid sporophytes produce spores via meiosis, which then divide by mitosis to produce the haploid gametophyte

Flower Layers

• Outermost whorl : sepal
• Second whorl comprises of petals
• Third whorl is the stamen
• Innermost whorl is the carpel

Flower Parts

• Carpel is the female part
• Ovary contains the ovule (megagametophyte) and becomes the fruit or seed
• Stigma is the tip where pollen lands and is sticky.
• Style is the neck that leads to the ovary.
• Stamen is the male part
• Anther contains the pollen grains (microgametophytes)
• Filament holds the anther up.

Pollen Formation

• Pollen forms inside the anther

Pollination

• Pollination is the mechanical transfer of pollen from the anther to the stigma.
• Double fertilization involves two sperm
  • One sperm unites with the egg to form a diploid zygote.
  • The other unites with the polar nuclei to form a triploid endosperm, which provides nutrients to the embryo.

Pollination Types

• Self-pollination pollen is deposited on the stigma of the same flower or another flower on the same plant.
• Cross-pollination transfers pollen from the anther of one flower to the stigma of another flower on a different plant of the same species.

Pollination Agents

• Biotic agents include insects, bats, birds, and other animals.
• Abiotic agents are wind and water.

Preventing Self-Pollination

• Pollen and the ovary can mature at different times.
• Physical features on the flower can prevent self-pollination.
• Male and female flowers can be located on different parts of the plant.

Seed Parts

• Integument is the protective covering and the parent sporophyte.
• Endosperm is the parent gametophyte.
• Embryo is the new offspring.

Seed Germination

• Seeds need water, oxygen, and the right temperature to germinate.
• Seeds remain dormant, conserving energy and protecting the embryo.

Seed Adaptations

• Dispersal adaptations
  • Fluff/fur aids wind dispersal (dandelions)
  • Sticky coatings help attach to animals
  • Fruity flesh encourages animal consumption and dispersal through feces
  • Buoyancy enables water dispersal (coconuts)
• Survival adaptations
  • Hard seed coats protect against damage and drying
  • Chemical inhibitors prevent germination under unfavorable conditions
• Timing adaptations
  • Dormancy delays germination
  • Temperature/light cues ensure growth occurs in the right season or time

Fruits

• Fruits are mature ovaries (carpels).
  • Exocarp: skin or rind
  • Mesocarp: flesh or pulp
  • Endocarp: pit that surrounds the seed

Asexual Reproduction

• Stolons (runners) are stems that run along the ground.
  • Stolons form adventitious roots and buds that grow into a new plant.
• Grafting involves grafting part of a plant's stem onto the root of another plant.
• Cuttings portion of a stem is placed in moist soil and allowed to take root.
• Layering a stem is bent and covered with soil to encourage root formation

Body Symmetry

• Radial symmetry features a central axis, bisecting into two equal halves.
• Bilateral symmetry features left and right halves as mirror images and only a midsagittal plane bisects into exact halves

Body Sectioning

• Frontal/coronal sections separate ventral (front) from dorsal (back).
• Transverse sections are akin to cross-sections.
• Sagittal sections divide left from right; midsagittal sections create mirror images.

Body Size Factors

• Getting nutrients through diffusion
• Surface area-to-volume ratio
• Not having larger cells and instead having more cells
• Gravity
• Drag in water
• Skeleton weight (endoskeleton and exoskeletons)

Ectotherms vs. Endotherms

• Basal Metabolic Rate is the average amount of energy used by an organism in a non-active state.
• Metabolic Rate is the amount of energy expended by an animal over a specific time.
• Ectotherms lack insulation, increasing dependence on the environment for body heat.
• Endotherms maintain constant body temperature and have a higher metabolic rate.

Metabolic Rates

• Small endothermic organisms have a higher BMR than larger ones.
• Active animals have a higher BMR than inactive ones.

Acclimatization

• Acclimatization involves changes in one organ system to maintain a set point in another organ system.

Feedback Loops

• Positive feedback loops maintain the response to a stimulus, ex. blood clotting and childbirth.
• Negative feedback loops counteract internal changes most biological systems are regulated by negative feedback loops, ex temperature, glucose, pH, and blood calcium level

Thermoregulation

• Radiation: heat released (heat from sun)
• Convection: air/water removes heat (using a fan, taking a cold bath)
• Conduction: heat transfers from surface (steam coming off a cup)
• Evaporation: sweating

Parazoa vs. Eumetazoa

• Parazoa lack tissues and organs.
• Eumetazoa have well-defined tissues.

Epithelial Tissues

• Simple Squamous: flat, irregular, round shape
• Simple Cuboidal: cube-shaped, central nucleus
• Simple Columnar: tall, narrow, base of nuclei
• Pseudostratified Columnar

Connective Tissues

• Connective tissues are composed of cells, fibers, and a gel-like substance; they contain collagen, elastin, and reticular fibers.
  • Bone, cartilage, fat, blood, and lymphatic tissue

Types of Connective Tissues

• Blood
• Loose connective
• Adipose
• Cartilage
• Bone
• Dense

Types of Muscle Tissues

• Skeletal muscle is voluntary, striated, and multinucleated.
• Smooth muscle is involuntary and lacks striations.
• Cardiac muscle is involuntary, striated, and has intercalated discs.

Nervous Tissue Cells

• Neurons transmit signals
• Glial cells support neurons

Neuron Structure

• Cell body: large structure with a central nucleus
• Dendrites: receives input.
• Axon: transmits impulses.
• Myelin: insulates, speeds up impulse transmission, and surrounds the axon

Essential Nutrients

• Essential nutrients must be obtained from food, aid in structure and regulation, and many act as cofactors and coenzymes.
• Essential nutrients cannot be assembled from simpler organic molecules.
  • Carbohydrates: sugars, starch, fiber found in milk, sugar, potatoes, corn, and fruit
  • Fiber: undigestible carbohydrate found in beans, peas, nuts, fruits, and veggies
  • Protein: essential amino acids found in meat, milk, and eggs
  • Lipids: fats, oils, and cholesterol protecting organs and insulating temperature found in butter, meat, olive oil, and avocado oil.
  • Vitamins: Organic compounds the body can't produce but are needed for metabolic processes.

Reproduction

• Asexual reproduction: 1 parent with identical offspring
• Sexual reproduction: 2 parents with genetic variation

Asexual Reproduction Methods

• Budding
• Splitting
• Regeneration from fragments
• Sponges
• Jellyfish, corals
• Flatworms
• Worms and leeches
• Starfish

Fertilization

• Fertilization is the union of sperm and egg to form a zygote.

External Fertilization

• Advantages: higher genetic diversity.
• Disadvantages: low survival and requires water.

Internal Fertilization

• Protects fertilized egg from dehydration.
• Limits predation.
• Enhances the fertilization of eggs by a specific male.
• Higher survival rate.

Animal Sexes

• Dioecious: separate sexes (humans)
• Monoecious: both sexes in one individual (worms, snails, slugs)

Invertebrate Reproduction

• External fertilization
• Simpler reproductive system
• Hermaphroditism

Human Reproduction

• Internal fertilization
• Complex hormonal regulation
• Separate sexes

Modes of Reproduction

• Oviparous animals lay eggs with yolk: reptiles and birds.
• Viviparous animals are live-born with zygotes and embryos cared for by a placenta: mammals and humans.
• Ovoviviparous animals hatch eggs inside the body.

Sperm Path

• Testes > epididymis > vas deferens > urethra > OUT

Semen

• Semen is composed of sperm cells and fluid.
• The fluid comes from seminal vesicles, prostate gland, and bulbourethral glands.
  • These fluids nourish sperm, protect them from acidity, and aid their swimming.

Sperm Parts

• Head holds DNA and the acrosome.
• Midpiece contains mitochondria
• Flagellum is the tail.

Spermatogenesis

• Spermatogenesis occurs in the seminiferous tubules of the testes.

Hormone Regulation

• The hypothalamus controls hormonal secretions.
• The pituitary gland produces FSH and LH.
• Testosterone is produced in the testes.

Egg Path

• Ovary > fertilization > uterus > cervix > vagina > birth
• Fertilization occurs in the fallopian tubes.

Ovarian Hormones

• Estrogen
• Progesterone

Ovarian Cycle

• Follicular Phase: FSH promotes development; the follicle then secretes estrogen.
• Ovulation: Release of secondary oocyte; follicle develops into corpus luteum.
• Luteal Phase: LH promotes development of corpus luteum, which secretes progesterone and degenerates without pregnancy.
• Ovulation typically occurs on Day 14.

Endometrium

• The endometrium thickens in preparation for pregnancy and sheds if there is no pregnancy, period

Uterine Cycle

• Menstruation begins on Day 1 of the uterine cycle.

Egg and Sperm Life

• Egg: 24 hours
• Sperm: up to 5 days

Menopause

• During menopause, the ovaries stop releasing eggs
• Hormone levels rise in females as they age.

Infertility

• Female: endometriosis
• Male: low sperm count