﻿ROOTS 
  AND 
  THEIR 
  RELATION 
  TO 
  PLANTS 
  23 
  

  

  is 
  called 
  turgidity. 
  Turgor 
  doubtless 
  helps 
  to 
  force 
  water 
  up- 
  

   ward 
  through 
  the 
  stem. 
  The 
  distention 
  of 
  cells 
  due 
  to 
  turgor 
  

   also 
  accounts 
  for 
  the 
  rigid 
  or 
  erect 
  position 
  of 
  most 
  leaves, 
  

   growing 
  shoots, 
  and 
  succulent 
  stems. 
  Each 
  distended 
  cell, 
  like 
  

   an 
  inflated 
  balloon, 
  assumes 
  a 
  semi-rigid 
  position, 
  and 
  a 
  mass 
  of 
  

   distended 
  cells 
  pressing 
  against 
  one 
  another 
  makes 
  the 
  whole 
  

  

  FIG. 
  17. 
  A 
  young 
  cucumber 
  plant 
  (grown 
  in 
  a 
  flowerpot) 
  

  

  At 
  left, 
  in 
  normal 
  condition 
  ; 
  at 
  right, 
  much 
  wilted 
  from 
  having 
  been 
  left 
  

   unwatered 
  for 
  several 
  days 
  

  

  structure 
  rigid. 
  But 
  just 
  as, 
  when 
  the 
  air 
  escapes 
  from 
  a 
  balloon, 
  

   its 
  wall 
  collapses 
  of 
  its 
  own 
  weight, 
  so 
  the 
  cells 
  of 
  the 
  leaves 
  and 
  

   shoots 
  collapse 
  when, 
  on 
  account 
  of 
  loss 
  of 
  water, 
  they 
  lose 
  

   their 
  turgidity. 
  When 
  soil 
  water 
  is 
  not 
  available 
  to 
  the 
  plant, 
  

   the 
  outgo 
  from 
  the 
  leaves 
  is 
  often 
  greater 
  than 
  the 
  income 
  from 
  

   the 
  roots, 
  and 
  in 
  such 
  cases 
  wilting 
  follows 
  (fig. 
  17). 
  If 
  water 
  

   does 
  not 
  again 
  become 
  available, 
  the 
  plant 
  will 
  die, 
  but 
  with 
  a 
  

   renewed 
  supply 
  turgidity 
  and 
  the 
  resulting 
  rigidity 
  soon 
  return. 
  

  

  