CHAPTER VI 



RELATION OF TURGOR AND OF TENSION 



TO GROWTH 



An important condition for growth is the supply of 

 water to the growing region, so that the cells may be in a 

 turgid state. The favourable condition of turgor can only 

 be assured by the pumping up of water from the soil, 

 growth being thus dependent upon the ascent of sap. 

 I will first describe the effects induced in growth by 

 changes in the rate of ascent of sap. 



Growth Revived after Irrigation 



Experiment 26. Growth-arrest and revival.- — The ex- 

 periment was carried out with a seedling of Cucurbit a 12 cm. 

 in height, growing in a small pot. Under excessive drought 

 the growth of the plant had been brought to a state of 

 standstih. The stem was held at its lower end in a clamp 

 and 2 c.c. of water was supphed to the root, growth becoming 

 revived after a latent period of 11 seconds. This delay 

 was due to the time taken for the water to reach the growing 

 region, and to impart sufficient turgidity to the cells for 

 the initiation of growth. It was interesting to find the 

 growth-record exhibiting pulsations {see fig. 23). The 

 small quantity of water supplied was sufficient to maintain 

 growth for only 3 minutes, after which it came to a stand- 

 still. Another 2 c.c. of water was next applied, resulting in 

 a renewal of growth for about 4 minutes or so ; the latent 

 period was, however, considerably reduced. The shortening 



