14 TRANSLOCATION OF PLANT FOOD IN WHEAT SEEDLINGS. 



The seedlings were grown nine days, a set of controls being grown 

 in distilled water in every case. The table gives the percentage of 

 increased absorption of each salt under the various conditions as com- 

 pared to that observed in the case of the plants grown in the control 

 solutions. The results show that when nitrates are present the ab- 

 sorption of that element by the axes is from 35 to 43 per cent greater 

 than it is in a water culture containing no nitrates ; when phosphates 

 are present the absorption is increased from 26 to 35 per cent, and when 

 potash is present the avidity which young plants display for this ele- 

 ment causes it to absorb from 140 to 200 per cent more of this con- 

 stituent than when grown in a water culture. It will also be noted 

 that the presence of nitrates not only causes an increased nitrate 

 absorption, but also seems to produce a slight increased absorption 

 of potash and phosphoric acid. 



The curve platted in figure 2 indicates that on the ninth day the 

 seed grown in water still retained about 30 per cent of its original 

 amount of phosphate. Part of this amount seems to have been given 

 up to the plantlet under the influence of the nitrate stimulus. The 

 same fact is noted when potash is added to the solution. In this case 

 an increased absorption of from 140 to 200 per cent of potash, and of 

 from 10 to 20 per cent of phosphoric acid occurs. No appreciable 

 increase in absorption of nitrogen or potash is noted under the phos- 

 phoric-acid stimulus. 



Another point to be observed is that the presence of 150 parts per 

 million of phosphoric acid, nitrate, or potash, respectively, in the 

 solution did not cause any increased absorption of any one salt by 

 the plant over what was taken up when it grew in a solution contain- 

 ing only from 50 to 100 parts per million, showing that as long as the 

 little plant has plenty of food at its command the addition of a larger 

 amount will not cause it to absorb a correspondingly larger quantity. 

 As the table shows, the amount of potash absorbed by the plant grow- 

 ing in the potash solution is far greater than the amount of nitrogen 

 and phosphoric acid absorbed by the plants grown in the nitrate and 

 phosphoric acid solutions, respectively. At the end of nine days the 

 plant contains approximately three times as much potash as was pres- 

 ent in the original seed, or an increase of about 200 per cent, which 

 leads to the conclusion that plants need large amounts of potash dur- 

 ing the early stages of growth. 



Another possible conclusion to be drawn from this table is that 

 young plants do not absorb a very great amount of phosphates even 

 when these salts are present in rather large quantities. The nitrates 

 are taken up somewhat more readily than the phosphates, but not 

 nearly to the extent that potash is absorbed. In other words, the 

 plants exert a selective absorption, assimilating a large amount of 



