BIOL134 Experiment Design Plan

Plant  Transpiration  Research  Project    

  VERNIER  PLANT  TRANSPIRATION  RESEARCH  PROJECT    

Plant  Transpiration  Research  Project    

Project  Guide  

Introduction  from  Vernier   Water  is  transported  in  plants,  from  the  roots  to  the  leaves,  following  a  decreasing  water  potential   gradient.  Transpiration,  or  loss  of  water  from  the  leaves,  helps  to  create  a  lower  osmotic  potential  in  the   leaf.  The  resulting  transpirational  pull  is  responsible  for  the  movement  of  water  from  the  xylem  to  the   mesophyll  cells  into  the  air  spaces  in  the  leaves.  The  rate  of  evaporation  of  water  from  the  air  spaces  of   the  leaf  to  the  outside  air  depends  on  the  water  potential  gradient  between  the  leaf  and  the  outside  air.     Various  environmental  factors,  including  those  conditions  which  directly  influence  the  opening  and   closing  of  the  stomata,  will  affect  a  plants  transpiration  rate.  This  experiment  will  measure  the   transpiration  rates  under  different  conditions.  You  will  choose  to  study  the  impact  of  light,  humidity,   temperature,  species  or  air  movement  and  the  impact  it  has  on  transpiration.  

    After  reading  through  the  direction  make  sure  to  watch  the  video  showing  the  procedure  in  action.      

Safety  Precautions   Make  sure  to  use  good  lab  work  practices  and  handle  and  dispose  of  sharps  appropriately.  Keep  a  close  

eye  on  your  pressures  and  make  sure  your  gas  sensor  does  not  get  wet  (this  will  ruin  the  sensor)  

Plant  Transpiration  Research  Project    

Lab  Materials   Vernier  LabQuest   Vernier  Gas  pressure  sensor  w/  tubing  set     Plastic  syringe  from  Vernier  kit   Vernier  Logger  Pro  (installed  on  computer)   plant  cutting  (stem  must  fit  within  gas  sensor  tubing  plants  that  work  well  are  tomato,  strawberry,  bean,   geranium,  cyclamen  etc.)   utility  clamps,  clothes  pins,  tape  or  string   razor  blade  or  scalpel   Tap  water   Large  bowl  or  container  to  submerge  gas  tubing  and  plant   Pipette  (HOL  kit)   Ruler  (HOL  kit)   Something  to  function  as  a  stand  to  clamp  the  plant  and  tubing  onto  (chair  leg  or  back,  legos,  railing  etc  )   Petroleum  jelly  (optional  but  very  helpful)     Depending  on  your  treatment  you  may  need:   Small  Lamp   Fan  with  a  slow  speed   Heater  (small  electric)   large  plastic  bag  &  water  spray  bottle   A  second  plant  species    

Variables:   You  can  modify  this  lab  to  test  the  effect  of  light,  humidity,  air  movement,  species,  and  temperature  on  

the  rate  of  transpiration.    Choose  1  independent  variable  to  test.  Below  are  lists  of  variables  and   some  ideas  on  how  to  test  them:    

  Light:    Test  the  plant  transpiration  at  different  light  levels.  Run  the  experiment  with  the  plant  under  dark  

conditions,  normal  daylight  and/or  under  bright  light  (have  a  small  lamp  shine  directly  on  the  leaves)     Temperature:    Subject  the  plant  to  2  different  temperature  settings.  You  can  use  a  small  heater  to  

increase  the  temperature  nearby  the  plant.  DO  NOT  use  a  hair  drier.  The  hair  drier  also  changes  air   movement  thus  you  cannot  isolate  the  effect  of  heat  alone.  

Plant  Transpiration  Research  Project    

      Humidity:  You  can  change  the  humidity  by  filling  a  large  plastic  bag  with  water  vapor  and  cover  and  seal  

the  plant  sample  within  the  bag.    

    Air  Movement:  Place  a  fan  with  a  low  speed  setting  near  your  plant.  Slight  air  movement  should  blow  

across  the  surface  of  the  leaves.  Too  much  air  movement  can  damage  the  leaves.       Species:  Choose  2  different  plant  species.  Evaluate  and  compare  the  rate  of  transpiration  of  the  different  

plants.       If  you  have  an  idea  for  another  variable  not  on  this  list  that  you  would  like  to  test,  please  send  me  a  

message  for  pre-­‐approval.  

  The  procedure  detailed  below  can  be  seen  in  the  video  link  provided  in  the  assignment  directions.  It  is   imperative  that  you  have  an  airtight  seal  on  all  the  tubing  for  the  experiment  to  work.  You  will  repeat  this   procedure  using  your  treatment.  Make  sure  you  keep  your  data  organized  and  separate.    Petroleum  jelly   around  the  end  of  the  gas  tubing  where  the  plant  was  inserted  can  help  with  the  air  tight  seal  (See  the   video  link  provided  for  how  to  use  the  petroleum  jelly)  

Plant  Transpiration  Research  Project    

Plant  Transpiration  Research  Project    

Plant  Transpiration  Research  Project    

  You  will  repeat  this  procedure  using  your  treatment.  Make  sure  you  keep  your  data  organized  and   separate.     Petroleum  jelly  around  the  end  of  the  gas  tubing  where  the  plant  was  inserted  can  help  with  the  air  tight   seal  (See  the  video  link  provided  for  how  to  use  the  petroleum  jelly)    

Plant  Transpiration  Research  Project    

Plant  Transpiration  Research  Project