78 TRANSLOCATION IN PLANTS 



system the tops promptly wilted. It would seem that 

 these plants were making considerable growth after the 

 roots were dead and were absorbing the soil solution directly 

 through nonliving tissues. 



I have found that bean plants are able to develop fairly 

 well and remain fresh for several weeks, and even mature 

 pods, after the main stem had been scalded when only the 

 first pair of leaves had formed. Although the roots were 

 not examined, they, in all probability, were dead while 

 the tops were still fresh. Chang (1932) found that leaves 

 of bean plants with killed roots absorbed more nitrogen 

 during the day than did those of check plants. Kramer 

 (1933) has found that roots killed by heat may continue 

 to be effective in absorbing water, for the plants so treated 

 remained alive and unwilted for several days. 



It would be of interest to determine the influence of 

 transpiration upon salt absorption of such plants with 

 dead roots. One could expect in this case some direct 

 relation between the amount of salts absorbed and the 

 amount of transpiration, because living cells with high 

 semipermeability would be absent. Any treatment tending 

 to injure the roots or increase their permeability can be 

 expected to favor more direct absorption of unaltered soil 

 solution, or bring about contamination of the transpiration 

 stream with the leachings from weakened cells. Such 

 injury may result from toxic agents, pathogens, poor 

 aeration, or starvation of the roots resulting from heavy 

 defoliation or pruning of the tops. Strasburger (1891, 

 p. 865) recognized that salts which do not readily enter 

 living roots will enter when the latter are killed. 



Even in plants with living healthy roots, the concentra- 

 tion of salts in the soil solution could be expected to have 

 an influence on the relative amounts transported through 

 the xylem and phloem. For example, with a low amount 

 of available nitrogen in the soil, one would expect the living 

 cells of the root to retain that absorbed, and perhaps 

 synthesize organic nitrogen compounds, which in all likeli- 

 hood would be retained by the living cells and transported 



