Biology 172 unit 1

• The radicle is the embryonic root of the seed.
• Trophic responses or tropisms are?

  Growth responses towards or away from a stimulus.
• Gravitropism 


  Growth response to gravity, can be negative or positive
• Thigmotrophism 


  Growth response to touch o contact with another object due to ethylene
• Phototrophism 


  The growth response f plants towards or away from a light source
• An auxin is responsable forthe growth towards unilateral light source
• Blue light enables strongest response to phototropism
• Turgor movement 


  a reversable movement that can reoccur over and over again, such as those exibited with a venus fly trap
• Phytochrome


  A red-light receptor
• Photoperiodism 


  a physiological response that occurs as a result of changes in day and night length
• Florigen 


  the flowering hormone
• Phloem transport goes from source to sink
• Source


  Where sugar is produced and stored (Leaves, rhizomes, tubers, and bulbs)
• Sink


  The destination to which food is transported and needed
• Once is sieve tube ,in angiosperms, movement is by bulk flow driven by positive pressure
• In xylem sap, movement is driven by negative pressure
• Reactions of plant hormones many vary according to concentration
• IAA - Auxins

  Cell elongation or growth
• Apical Dominance


  when IAA causes the apical meristem to inhibit axillary buds from forming branches
• GA - Gibberellic Acids


  Stem elongation, breaking seed dormancy, and fruit growth
• ABA - Abscissic Acid


  Functions in dormancy of seeds an opening/closing of stomata
• CK - Cytokinins 


  Stimulates cell division, and slows senescence in leaves
• Senescence


  process of deterioration with age
• Ethylene


  Inihiting hormone, also functions in "triple response", leaf abscission and fruit ripening
• Leaf abscission 


  shedding of a leaf
• Apical Dominance


  When the main central stem grows more strongly than the other side stems
• Phyllotaxy


  The arrangement of leaves on a stem
• Alternate or spiral arrangement is when leaves are arranged on alternate sides of the stem
• Opposite leaf arrangement has two leaves on opposite sides of the same nodes
• Whorled leaf arrangemet has three or more leaves on the same node
• Apoplasts

  Non-living components of cell, i.e. cell wall ad intercellular space
• Symplasts

  Living components of cell, i.e., protoplasts and plasmodesmata
• Transmembrane 


  Both apoplasts ad symplast occurs
• Casparian strip


  On radial wall and is impermeable to water, allowing selection as to what ions are allowed to go through
• Stomata formed by a pair of guard cells that become turgid when open and flaccid when closed
• Stomata

  Regulate transpiration and maximize photosynthesis
• Transpiration

  The evaporation of water through stomata
• Transpiration creates a negative pressure which pulls xylem sap up
• High humidity --> Slow transpiration
• Low humidity --> Increased transpiration