gen bio 2 prelim

• Plant nutrients are available as irregular patchy distribution in most soils.

  Leads to limited accessibility of nutrients for plants.

  Plants trigger physiological and developmental responses to acquire nutrients.

  Adaptive mechanisms also utilized by plants to increase or decrease growth in organs that directly or indirectly participate in nutrient acquisition.
• What are Plant hormones?

  also known as phytohormones

  Chemicals that regulate plant growth.

  Hormones regulate cellular processes in targeted cells locally and, moved to other locations, in other functional parts of the plant.

  Hormones also determine the formation of flowers, stems, leaves, the shedding of leaves, and the development and ripening of fruit.

  Plant hormones also play an important role in plant defense against pathogenic microorganisms. Not only do these plant hormones perform such functions, but they also regulate development and signals networks in plants.
• Light is the most important stimulus for plants as it could spell their survival or demise. The plant’s response to light is mediated by photoreceptors that is composed of a protein bound to a light-absorbing pigment called chromophore. It can trigger structural development and growth in plants. It provides energy and the main source for photosynthesis. 
• Abscisic Acid

  • Lateral root inhibition
  • Nutrient starvation stress-protecting hormone
  • Seed germination
  • Leaf senescence
  • Stomatal aperture
  • Adaptation to environmental stress
  • Embryo maturation
  • Plant pathosystems defense response
• Auxin

  • Antagonistic effect on disease susceptibility and resistance
  • Defense response against biotrophic and necrotrophic pathogens.
  • Stimulates cell elongation from wall loosening factors (elastin)
  • Induces growth of pre-existing roots
• Brassinosteroids acid

  • Structurally related to animal steroid hormones for growth, development and physiological responses
  • Abiotic stress responses
  • Seed germination
  • Reproductive development
  • Regulate plant defense from pathogens
• Cytokinin

  • Promotes cell division
  • Activation of cytokinensis
  • Seed development
  • Regulation of stem cell related genes
  • Slow down plant aging
  • Chloroplast formation
• Ethylene

  • Affects ripening and rotting of plants.
  • Stimulating the production of flowers
  • Senescence
  • Responses environmental stresses
• Gibberellins

  • Response to nutritional limitation
  • Promote stem elongation between nodes on the stem.
  • Induced fruit enlargement.
• Jasmonic acid

  • Defense from necrotrophic pathogens and herbivore insects such as caterpillar, beetles, leafhoppers and spider mites
  • Leaf senescence and fruit ripening
  • Tuber formation
  • Stomatal opening
• Salicylic acid

  • Establish systemic acquired resistance
  • Activation of defense response from biotrophic and hemi-biotrophic pathogens
  • Inhibits seed germination
  • Increase seed vigour
• Plants exhibit growth or slight movement because of a stimulus. This process of growth in a certain direction in response to a stimulus is called tropism. Positive tropism is the growth toward the stimulus whereas negative tropism is growth away from a stimulus.
• Animal development

  Indirect - Involves one or more intermediate larval forms before the adult form is attained. 

  Direct - By the time they’re hatched or born, the young animals look more or less like smaller versions of their parents. 

  Metamorphosis - the process of transformation from an immature form to an adult form in two or more distinct stages. The animal undergoes a process of metamorphosis in which its body form changes from that of a larva to that of a sexually-mature adult. 
• Endocrine hormones are produced by endocrine (“ductless”) glands and secreted into the bloodstream.
• Endocrine hormones may affect a wide array of target cells to produce multiple effects.
• There are two types of endocrine hormones: peptides (small proteins) and steroids (lipids).
• Peptide hormones do not enter the cell directly.
• Peptide hormones bind to receptor proteins in the cell membrane.
• When the hormone binds with the receptor protein, a secondary messenger molecule initiates the cell response.
• Peptide hormones are water soluble, which often produces fast responses.
• Steroid hormones enter through the cell membrane and bind to receptors inside of the target cell.
• Steroid hormones may directly stimulate transcription of genes to make certain proteins.
• Because steroids work by triggering gene activity, the response is slower than peptide hormones.
• Cardiovascular lymphatic systems transport fluids throughout the body. It helps sense both solute and water levels and regulate pressure.
• Hypothalamus 

  • The thalamus receives sensory information, relays some to the hypothalamus.
  • Hypothalamus monitors the body for temperature, pH, other conditions.
  • Hypothalamus signals pituitary gland if conditions need to be corrected.
  • The hypothalamus of the brain plays a big role in stimulating the production of the sex hormones testosterone and estrogen from the testes and ovary
• • The pituitary is the “master gland” that signals other glands to produce their hormones when needed. 
• • The anterior lobe of the pituitary receives signals from the hypothalamus, and responds by sending out the appropriate hormone to other endocrine glands.
  • The posterior pituitary receives oxytocin or antidiuretic hormone (ADH) from the hypothalamus, relays them to the body as necessary.
• Cytokinin promotes cell division.
• Cytokinin activates cytokinensis.
• Cytokinin is involved in seed development.
• Cytokinin regulates stem cell related genes.
• Cytokinin slows down plant aging.
• Cytokinin is involved in chloroplast formation.
• Ethylene affects ripening and rotting of plants.
• Ethylene stimulates the production of flowers.
• Ethylene is involved in senescence responses to environmental stresses.
• Gibberellins are involved in response to nutritional limitation.
• Gibberellins promote stem elongation between nodes on the stem.
• Gibberellins are involved in induced fruit enlargement.
• Jasmonic acid is involved in defense from necrotrophic pathogens and herbivore insects such as caterpillar, beetles, leafhoppers and spider mites.