76 TRANSLOCATION IN PLANTS 



influence of transpiration on the movement of ash into 

 leaves of an intact plant. They found, for instance, that 

 immediately following a period of hot desiccating winds, 

 the ash content of the uninjured leaves of citrus was 

 higher than that of the leaves which had been killed by 

 the desiccation and therefore supposedly unaltered with 

 respect to ash. The data they offer, however, seem far 

 from conclusive. In the first place it is possible that 

 different leaves had a different composition to begin with, 

 and the desiccating winds tended to kill those of one 

 composition, those which had low total ash, low calcium, 

 high potassium, high sulphate and high phosphate, while 

 the others which were not killed, instead of changing in 

 composition may have originally had a different composi- 

 tion. In the second place, though their data seem to show 

 a clear increase in the calcium content of the ash and a 

 very slight increase in the content of magnesium and 

 chlorine, they at the same time show a decrease in the 

 potassium, sulphate, and phosphate content of the ash, 

 and though the differences were not great they are of the 

 same order as the calcium change if expressed in percentage 

 of the original contents. 



Though the wilted leaves 10 days after regaining turgor 

 tend to have an ash composition more nearly like that of 

 the killed leaves, some of the constituents show an ash 

 content even less than before the wilting. Furthermore, 

 since the ash contents are expressed in terms of dry weight 

 only, some of the differences, especially the gain of total 

 ash during the hot dry period and the apparent loss of ash 

 after recovery of turgor, may have been due, respectively, 

 to an effect of desiccation and heat on the loss of dry matter, 

 and an effect of regained turgor and lower temperature 

 upon reformation of carbohydrates in the leaves, and not 

 to any effect of changed transpiration on absolute ash 

 content. It seems very possible that high temperature 

 and low water supply might reduce the carbohydrate 

 content by decreasing photosynthesis and increasing 

 respiration, thus causing an apparent temporary increase 



