Hodgson: Abnormal Water Belations in Citrus Trees 41 



TABLE 1 

 AVERAGE MOISTURE CONTENT 



Average water content 



in per cent 

 Kind of material (Dry weight) 



New leaves about two weeks old ................................................ 242.0 



Full grown leaves of current season 's growth ........................ 162.2 



Leaves of one season's growth about one year old ............ 132.7 



Leaves of two season's growth about two years old ........ 126.1 



Leaves of three or more season's growth. Over two years 



old ................................................................................................ 117.6 



Leaves of current season's growth. Gathered between 



9 A.M. and 12 P.M ....................................................................... 164.9 



Same gathered between 1 P.M. and 4 P.M ................................. 157.2 



Leaves of current season 's growth gathered from behind 



fruits between 9 A.M. and 12 M ............................................. 166.8 



Same gathered between 1 P.M. and 4 P.M ................................. 160.4 



Fruits destined to subsequent abscission, one-third to three- 



fourths inch in diameter ........................................................ 191.5 



Fruits apparently normal gathered between 9 A.M. and 12 M.s 260.2 



Same gathered between 1 P.M. and 4 P.M ................................... 247.7 



Fruits destined to subsequent abscission gathered between 



9 A.M. and 12 M ....................................................................... 201.4 



Same gathered between 1 P.M. and 4 P.M ................................. 179.2 



of the fact that as the leaves grow older there is a progressive decrease 

 in water content. 



It is also quite evident that a regular diurnal decrease in the water 

 content of leaves of the current season's growth is manifest during 

 the afternoon. Such leaves averaged 164.9% in water content for the 

 period between 9 A.M. and 12 M. and only 157.2% for the period 

 between 1 P.M. and 4 P.M. This difference does not appear significant 

 when viewed in the light of the large differences obtained by Living- 

 ston and Brown with some of their material. However, it should 

 be borne in mind that those authors were dealing, for the most part, 

 with much more succulent plants containing a large amount of water 

 storage tissue. Further, it should be noted that these figures are 

 averages, since the determinations on which they are based were not 

 made at the same hours. Individual pairs of determinations fre- 

 quently showed differences of as much as 25% to 30% in as short a 

 period as six hours. On June 5 at 2 :30 P.M., with the temperature at 

 95 F and the relative humidity at 19%, the water content of leaves 

 of the current season's growth was 144.3%. At 4 A.M. the next morn- 



s The fruits used for these determinations averaged a little larger than 

 those gathered in the forenoon and therefore would normally be somewhat 

 higher in water content. 



