variation of turgor 



Effect of Positive and Negative Variation 



OF Turgor 



55 



The acceleration of growth by the enhancement of 

 turgor caused by increased rate of ascent of water having 

 been demonstrated by the last experiment, 

 I then proceeded to observe the effect of 

 diminution of turgor in the very same organ. 



Experiment 30. Effect of alternate 

 supply and withdrawal of water. — The rate 

 of growth of the peduncle of Zephyranthes 

 in the condition of partial drought was, 

 as already stated, 0-04 ]x per second, 

 increased to 0-20 [l after irrigation with 

 warm water. The permanent rate of growth 

 after irrigation was found to be o-o8 \l 

 per second. A strong solution of KNO3 

 was then applied to the root in order to ^^*^; ^5- The 

 withdraw water, with the result that the nate application 



and withdrawal 

 of water on 

 growth, 



N, normal rate 

 under drought ; 

 H, enhanced rate 

 after irrigation 

 with warm 

 water ; n', sub- 

 sequent per- 

 manent rate ; p, 

 diminished rate 

 of growth after 

 plasmolytic 

 withdrawal of 

 water (Zephy- 

 ranthes). 



rate of growth quickly declined to 0-03 (x 

 per second, being nearly one-third the 

 previous rate (fig. 25). The induced de- 

 pression was thus greater than that under 

 condition of drought. The table shown on 

 page 56 is a statement of the results. 



The results given show that the rate 

 of growth is enhanced, within limits, by an 

 increase of turgor due to more rapid supply 

 of water ; withdrawal of water, on the 

 other hand, brings about a retardation or 

 negative variation in the rate of growth. 

 Protoplasmic activity underlies both the movement of 

 growth and the ascent of sap. 



Effect of Gain or Loss of Water on Motile 



AND Growing Organs 

 In my previous work, ' The Motor Mechanism of Plants,' 

 it has been shown that the response of a motile organ is 



