Martin : Effect of concentrated solutions 425 



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^/3 glycerine, and nJ2 acetamid. But the glycerine produced as 

 great an osmotic pressure as the acetamid. 



The action of acetamid in general seems to differ markedly 

 from that of glycerine and urea. The latter substances produce a 

 final concentration in the cell considerably higher than that of the 

 plasmolyzing solution. For example, in the experiments Just 

 quoted the ;//3 glycerine required an ;?/2 potassium nitrate to 

 produce replasmolysis. But acetamid produces a final osmotic 

 pressure equal to that of the solution used to plasmolyze the 

 cells. An 71J2 acetamid required an ///2 potassium nitrate to pro- 

 duce replasmolysis. 



The above variations in the increase of concentration tend to 

 show that the time necessary for the recovery of turgidity needs 

 to be considered. After treatment with glycerine or urea, which 

 require several hours for the plant to recover turgidity, a stronger 

 concentration of potassium nitrate is required for replasmolysis, 

 than after treatment with acetamid, in which the plant quickly 

 regains turgidity. This was shown not only in Philotria but to a 

 less extent in Tradescantia, — In PJiilotria it requires from ^nlio 

 to 2/// 5 potassium nitrate to replasmolyze cells which have been 

 plasmolyzed w^ith ;//3 solutions of glycerine or urea, whereas ;//3 

 potassium nitrate produced plasmolysis in cells treated with ;^/3 

 acetamid. During the hours in which turgidity is being restored 

 in cells plasmolyzed by glycerine or urea, osmotically active pro- 

 ducts may be formed in the cells. The short time required for 

 turgidity to be restored in acetamid, as well as the fact that turgor 

 is not raised above the osmotic pressure of the plasmolyzing solu- 

 tion, would seem to show that the increased turgor, in this case, 

 was due, merely to the penetration of the surrounding solution. 



The strength of the solution used also has an influence on the 

 increase of sap-concentration. A more concentrated solution will 

 produce a greater increase in turgor than a/veaker solution. The 

 concentration of the sap in Philotria was increased 1.8 times in 

 ^IZ urea, but only 1.6 times in n!^ urea; or, expressed in terms 

 of the increase in per cent, of potassium nitrate, 2.03 per cent, in 

 «/3 urea, 1.52 per cent, in nj^ urea. Acetamid showed a marked 

 difference in Philotria. In nl2 acetamid the concentration was 



