EFFECT OF ASCENT OF SAP 



53 



Experiment 28. Effect of irrigation with cold and with 

 warm water. — A specimen of Kysoor with a quantity of soil 

 surrounding the root (enclosed in a small bag) was employed 

 for this experiment. The lower part of the plant was 

 securely fixed on a stand, the tip being attached to the 

 Crescograph. The specimen was then subjected to partial 

 drought, water being withheld for a day. This caused a 

 depressedrate of growth, but 

 not complete arrest. The 

 record D (fig. 24) exhibits 

 the depressed rate of growth 

 under partial drought. 

 Cold water was then applied 

 to the root and the effect is 

 shown in record C. Finally, 

 the record H was obtained 

 after irrigation with warm 

 water. It will be seen that 

 the spacings between suc- 

 cessive dots at intervals of 

 10 seconds in the three re- 

 cords are very different. 

 While a given growth-elon- 

 gation under drought took 

 place in 19 x 10 seconds, a 

 similar lengthening occurred 

 after irrigation with cold 

 water in 13 x 10 seconds, and 

 after irrigation with warm 

 water in 3 X 10 seconds. 

 Enhancement of the rate of ascent of sap by irrigation with 

 warm water is thus seen to have increased the rate of 

 growth more than six times (fig. 24). 



The interval between irrigation and responsive variation 

 of growth will obviously depend (i) on the intervening 

 distance between the root and the region of growth, and 

 (2) on the vital activity underlying the ascent of sap. This 

 activity is increased by the action of warm water. In the 



Fig. 24. Effect of irrigation on 

 growth. 



D, record of grou-th under partial 

 drought ; c, acceleration after 

 irrigation with cold water ; 

 H, enhanced acceleration of 

 gro^vth after irrigation with 

 warm water (S. Kysoor). 



