GENBIO2

• Plant transports


  Food, water, and minerals through its system
• Materials should be transported between the root system and the shoot system
• Xylem


  • Transports water and minerals in an upward direction
  • Its tracheary elements consist of cells: Tracheids & vessel
  • One way direction, from the root to shoots
  • Vessel element- wide, thin, hollow cells, sclerenchyma tissue. It transports & support
  • Tracheids- narrower, tapered cells; have pits at ends that allows water to transport
  • As water flows in, pressure is generated which forces the fluid to go up the xylem
  • Upward push of xylem sap is called root pressure
  • Can cause guttation which excludes water from margins of the leaf not through stomata
  • Xylem follows a straw analogy
• Phloem


  • Transports sugars and other items
  • Composed of sieve tubes with companion cells and various support cells
  • Sieve-tube elements- alive at maturity, long narrow with sieve plates at ends. No nucleus, ribosomes and vacuole
  • Companion cell- attached to the side of sieve-tube, organelles serve both cells, does not transport
• Phloem transport


  1. Sugar source- where sugar is being produced usually at the leaves

  2. Sugar sink- consumes or stores sugar usually at roots, growing stems, buds, and fruits

  3. Pressure is created at source as sugar is produced

  4. Pressure decreases in sink as sugar is used

  5. Translocation- Water diffuses into phloem from xylem due to decrease water potential & pushes the sugar source to sink
• Transport system in plants

  • Xylem: Water and minerals, no end walls between cells, one-way only, outer cells are not living, straw analogy, tracheids and vessel elements
  • Phloem: Organic molecules, end walls (sieve plates), two-way movement, cells are living but need support, sieve tube element and companion cell
• Vascular tissue arrangement


  • Arranged into bundles of xylem and phloem that are scattered throughout the ground tissue
  • Arrangement varies in dicot and monocot plants
• Dicot vascular bundle arrangement

  • Phloem, cambium, xylem
  • Epidermis
  • Cortex
  • Pith
• Monocot vascular bundle arrangement

  • Xylem, phloem
  • Epidermis
  • Ground tissue
• In order for plants to sustain their metabolic processes, inorganic nutrients are obtained from the environment via soil, air, and water
• Plant nutrients


  • Macronutrients from air/water: Carbon, Hydrogen, Oxygen (CHO)
  • Macronutrients from soils: Nitrogen, Phosphorus, Potassium, calcium, Magnesium, Sulfur (N, P, K, CA, MG, S)
  • Micronutrients from soils: Boron, Chlorine, Copper, Iron, Manganese, Molybdenum, Nickel, Zinc (B, CL, CU, FE, MN, MO, NI, ZN)
• Nitrogen


  Affects leaf growth and plant development for healthy green foliage
• Phosphorus


  Improves the roots, stems, flowers, and fruits
• Potassium


  Promotes photosynthesis and improves plant resistance
• Phytohormones


  Organic substances that regulate plant growth and development. Increase defense against pathogens and adapt to environmental stress
• Growth promoters


  • Auxin- promotes cell growth and elongation of the plant
  • Gibberellins (GA)- stimulate cell elongation and cause plants to grow taller. Response to nutritional limitation
  • Cytokinin (CK)- promotes seed development, cell expansion, cell differentiation, N assimilation
  • Salicylic acid (SA)- defense against a variety of biotic and abiotic stresses. Inhibit seed germination
  • Brassinosteroids (BR)- promotes cell division, expansion, elongation, development, and immunity
• Growth inhibitors


  • Ethylene (ET)- stimulates the opening of flowers, fruit ripening, and immunity (promote or inhibit growth)
  • Abscisic acid (ABA)- regulates plant growth, development, and stress responses
  • Jasmonic acid (JA)- defense from necrotrophic pathogens and insects. Fruit ripening, tuber formation, and stomatal opening
• All living organisms reproduce to ensure the continued existence of the species
• Asexual reproduction


  • Fission
  • Budding
  • Fragmentation
  • Parthenogenesis
• Asexual reproduction


  • Produces individuals that are genetically identical to the parent plant
  • Advantages include an increased rate of maturity and a sturdier adult plant
• Natural vegetative propagation


  • Rhizome (ginger)- underground stems that grow on the soil surfaces
  • Root propagation (sweet potato)- new root joins the old root tube
  • Tuber (potato)- much thickened underground part of a stem or rhizome
  • Bulb (onion)- describe geophytes, or plants that produce specialized underground stems where buds form
  • Leaf bryophyllum- leaf produces a bud that becomes a new plant
  • Runner (oxalis)- roots of the runner produces a root that becomes a new plant
  • Sucker (mint)- the sprout of the plant comes in contact with the soil that leads to a new plant
• Artificial vegetative propagation


  • Grafting
  • Cutting- a root, stem or leaf is removed from a plant and placed in optimum conditions
  • Layering- development of roots on a stem while the stem is still attached to the parent plant
  • Tissue culture- making new plants 'in vitro' under sterile conditions
• Apomixis


  Asexual mode of reproduction through seeds where progeny are clones of the mother plant. Occurring without fertilization of sexual gametes but with formation of embryo and seeds
• Sexual reproduction


  • Results from fertilization, union of gametes (cells that undergone meiosis) from 2 genetically different plants
  • Advantages include the increase genetic diversity of the population, enhancing the evolutionary viability of the species
• Pollination


  • The process by which pollen is taken from 'anthers' (male organ) to the 'stigma' (female organ)
  • Flowering plants are known as 'angiosperms'
  • Angiosperms have roots, stems, and leaves. They produce seeds and have male & female organs within the flower
• Pollination types


  • Self-pollination: pollen is transferred to or from any flower of the same plant
  • Cross-pollination: pollen comes from a flower on a different plant
• Gymnosperm


  • A leafy green sporophyte generates cones containing male and female gametophytes
  • Female cones are bigger than male cones and are located higher up in the tree
  • Male cone contains microsporophylls where male pollen are produced
• Sexual spores


  • The plants produce hundreds of spores and the spore sac bursts (sporangia)
  • Spores are dispersed into the air, where they germinate and create a new plant
• Modern biotechnological applications in plants

  • Plant tissue culture- use of small pieces of plant tissue which are cultured in a nutrient medium under sterile conditions
  • GM plant- technology that involves inserting DNA into the genome of an organism. To produce a GM plant, new DNA is transferred into plant cells, then grown in tissue culture where they develop into plants
• Benefits of GMOs


  • Nutritional value of foods could be improved
  • Crops can be produced that lack known allergens
  • Crops can grow in arid conditions for better yield
  • GM Crops can produce herbicides to kill pests
  • Improve food supply / agriculture in poor countries
  • Have longer shelf lives
  • Reduces economic costs and carbon footprint - less need for land clearing and pesticides usage
• Risks of GMOs


  • New traits could cause adverse health reactions
  • Removal of traits could have unknown effects
  • Crops may limit biodiversity of local environment
  • Cross pollination could lead to 'super weeds'
  • Patents restrict farmers from accessing GM seeds
  • Foods with GM components may not be labeled
  • Different governments may have conflicting regulatory standards concerning safe usage
• Every animal species ensure the survival of its lineage. The role of reproduction is to provide for the continued existence of a species
• Animal reproduction


  • Asexual reproduction: fission, budding, fragmentation, parthogenesis
  • Sexual reproduction: hermaphroditism, and separate sexes (external & internal fertilization)
• Asexual reproduction


  • Offspring are genetically identical to the parent
  • Advantages: Large number of offspring from a single individual, well adapted offspring in stable environments, easier colonization of new habitats
  • Disadvantages: Competition on the same types of sources, No genetic variation which disables them to survive in unstable environment
• Asexual reproduction types


  • Fission (binary fission)
  • Budding
  • Fragmentation
  • Parthenogenesis
• Fragmentation


  Breaking of the body into two parts with subsequent regeneration. Completely new organism is formed, unlike regeneration which repairs damaged parts
• Parthenogenesis


  An egg develops into a complete individual without being fertilized. Offspring can be haploid or diploid
• Sexual reproduction


  • Combination of haploid reproductive cells from two individuals to form a unique diploid offspring
  • Advantages: Genetically diverse offspring, Enhanced evolutionary viability in unstable environment
  • Disadvantages: Must maintain two sexes, Limit the ability to colonize new habitats
• Hermaphroditism


  Occurs in animals where one individual has both male and female reproductive parts. May self-fertilize or mate with another
• Separate sexes


  • Determined by the presence of a specific set of chromosomes. Environmental sex determination, sex reversal
  • Mammalian sex is determined genetically by the presence of X and Y chromosomes
  • Avian: Homozygous (ZZ) results to male, Heterozygous (ZW) results to female. Fish, crustaceans, insects use this system
  • Mammal: Female (XX), Male (XY)
  • Turtles: cooler temperature (male), warm temperature(female)
  • Crocodiles: moderate temperature (male), warm & cool temperature(female)
  • Some species change their sex during their lives alternating between male and female