UPWARD TRANSPORT OF NITROGEN 77 



in ash. Maximov (1929, p. 241) reports an instance where 

 there was a loss of 40 per cent of the dry weight of leaves 

 of Impatiens during a five-day period of intense wilting. 

 He also states that Iljin observed a decrease of 15 to 

 30 per cent in absolute dry weight of wheat plants during 

 an excessively dry period. If a plant contained 3 per cent 

 nitrogen or ash and the dry weight decreased 40 per cent, 

 the percentage of nitrogen or ash would change from 3 to 

 5 per cent, an apparent increase of 66.6 per cent in spite 

 of the fact that there was no real change in total nitrogen 

 or ash. 



14. Absorption and Transport under Special Conditions. 

 Although much of the evidence points strongly toward 

 little or no direct effect of transpiration upon absorption 

 and transport of mineral salts, it can be easily demonstrated 

 that under special conditions the rate of transpiration may 

 greatly influence both absorption and transport. When 

 roots are supplied with toxic solutions, such as eosin for 

 example, the solute is absorbed and transported in the 

 transpiration stream. In fact it seems probable that 

 experiments with toxic dyes of this sort are partly respon- 

 sible for the widespread notion that transpiration deter- 

 mines absorption and transport of solutes. 



A high concentration of salts which are not usually 

 considered as toxic may result in injury to the absorbing 

 tissues and thus be carried with the transpiration stream. 

 Thus the addition of excess sodium chloride to the soil 

 will sometimes cause distinct "burning" of the leaf edges, 

 or death of entire leaves without apparent injury to the 

 stems or the lateral or terminal buds. It seems that in 

 these cases the salt has been carried with the transpiration 

 stream to the leaves, with much less injury to other tissues. 



Mr. Maguire has brought to my attention the fact that 

 plants of Galium may continue to grow for a considerable 

 period, developing flowers and fruits long after the lower 

 part of the stem as well as the roots seemed dead. When 

 behaving in this manner, the plants were growing in a soil 

 with plenty of moisture. When severed from the root 



