PHOTOTROPIC  RESPONSE  AND  CO,  ASSIMILATION 
OF  PLANTS  IN  POLARIZED  LIGHT 
By  earl  S.  JOHNSTON 
Dn'isioii  of  Radiation  ami  Organisms,  Smithsonian  Institution 
From  time  to  time  articles  I)Oth  scientific  and  popular  appear  on 
the  effects  of  polarized  light  on  plants.  Some  years  ago  Semmens 
(  1923)  reported  an  increased  velocity  of  seed  germination  in  moon- 
light and  suggested  that  the  plane  polarization  of  moonlight  affected 
the  diatase  activity.  Baly  and  Semmens  (1924)  reported  an  increased 
rate  of  hydrolysis  of  starches  in  plants  exposed  to  polarized  light. 
In  a  later  paper  Semmens  (1930)  characterizes  plants  grown  in  suc- 
cessive periods  of  darkness  and  polarized  light  by  a  disappearance  of 
starch  and  other  reserve  products,  such  as  glucosides,  a  temporary  pho- 
totropism  due  to  increased  stem  turgor,  and  a  leaf  fall  with  other  signs 
of  starvation.  On  the  other  hand,  du  Buy  and  Nuernbergk  (1935) 
mention  some  unpublished  experiments  in  which  they  found  no  differ- 
ence in  the  bending  of  Avena  coleoptiles  toward  polarized  and  non- 
polarized light.  Furthermore,  Dastur  and  Asana  (1932)  indicate  that 
the  process  of  photosynthesis  goes  on  as  vigorously  and  regularly  in 
polarized  light  as  in  ordinary  light.  Macht  (1926)  reports  evidence  of 
better  growth  of  Lupiuus,  wheat,  squash,  and  Helianthus  seedlings  in 
polarized  light  of  a  Mazda  lamp  than  in  his  controls.  Dastur  and  Gun- 
jikar  (1935)  report  that  leaves  of  12  different  species  clearly  show  a 
larger  amount  of  energy  absorbed  from  polarized  light  than  from  nor- 
mal light  of  ecjual  intensity.  May  (1924)  conducted  a  number  of  ex- 
periments over  a  year  to  determine  if  there  was  a  basis  of  fact  regard- 
ing the  seeding  of  crops  during  different  phases  of  the  moon.  He 
found  there  was  not  enough  difference  in  the  general  growth  to  be 
noticeable  to  the  eye,  certainly  not  enough  upon  which  to  found  a 
theory.  There  is  no  evidence,  as  pointed  out  by  Garner  (1937),  to 
show  that  the  moon  is  capable  of  exerting  any  effect  on  crop  plants 
other  than  those  due  to  its  action  on  illuminating  conditions. 
In  a  number  of  plant  growth  studies  conducted  at  the  Smithsonian 
Institution  it  has  been  necessary  to  direct  beams  of  light  on  the  plants 
by  means  of  mirrors.  Judging  from  some  of  the  discussions  in  the  lit- 
erature one  might  raise  the  question  as  to  the  effect  of  polarized  light 
on  growth  processes.  Especially  is  this  applicable  to  our  studies  on 
the  growth  of  the  oat  coleoptile  in  monochromatic  light  reflected  by  a 
Smithsonian  Miscellaneous  Collections,  Vol.96,  No.  3 
