Effect of Pressure on Groivth 265 



THE EFFECT OF PRESSURE ON GROWTH. 

 F. M. Andrews, Indiana University. 



Numerous experiments have been carried out to show the effect of 

 air pressure on plants. Among these may be mentioned the work of 

 Bert\ Later Wieler' studied the question of reduced pressure of oxygen 

 and Jentz' of increased oxygen pressure. Some of these facts are also 

 set forth by Pfeffer'. Czapek' also points out a number of interesting 

 researches on this subject. 



The points to be mentioned briefly here, however, refer to the effect 

 of water pressure on plant growth. That the roots of plants grow when 

 submerged in water is common knowledge but when the pressure of the 

 water is increased there is an effect which varies with the intensity of 

 the pressure. The writer noticed long ago that centrifuging caused the 

 roots of corn seedlings to become translucent due to the fact that part 

 of the water surrounding the seedlings was forced into the roots. For 

 example, the roots of the control or uncentrifuged seedlings retained 

 their normal color in water, but those which were centrifuged and sub- 

 jected to a force equivalent to a column of water 30 meters high, became 

 clear in 15 minutes. 



The combined action of centrifugal force and water pressure was 

 observed in another experiment. In this case control seedlings of corn 

 which were 3 cm. long grew 2 mm. in water in four hours at 24 "C. The 

 centrifuged corn seedlings of the same size and under exactly the same 

 conditions grew only 1 mm. in four hours, under a water pressure of 30 

 meters. Numerous other experiments performed in this way using both 

 smaller and greater amounts of water pressure verified these results. 



In another series of experiments the seedlings of corn were sub- 

 jected to water pressure without the action of centrifugal force. Corn 

 seedlings 3 cm. long and used as controls grew, on the average, 2.1 mm. 

 in four hours at 24 °C. in this set of experiments. The corn seedlings 

 3 cm. long and which were subjected to a pressure of 30 meters of water 

 grew 1.5 mm. in four hours at 24°C. The effect of pressure in this case 

 which was equal to a column of water 30 meters in height amounted, 

 therefore, to a growth check of .6 mm. in four hours. 



A third series of experiments was performed to test out the effect 

 of extremely high pressures on the growth of seedlings. Corn seedlings 

 2 cm. long were exposed to water pressure of 50 atmospheres at a 

 favorable temperature for five minutes. At the end of this time the 

 roots so treated were clear. These seedlings and other corn seedlings 2 

 cm. long used as controls were planted in sawdust. In 24 hours the 



1 Bert, p. Compt. rend. 1877 Tome 84 p. 1130. 



- Wieler, A. Die Beeinflussung des Wachsens durch veitninderte Partiarpressung 

 des Sauerstoflfs. Unters. a. d. Bot. Institut z. Tubingen 1833 Bd. I. p. 189. 



" Jentys, .Stefan. Ueber den Einfluss hoher Sauerstoffpressung auf das Wachstum 

 der I'/lanzen. Untei- a. d. Bot. Institut z. Tubingen 1886 Bd. II p. 419. 



^ Pfeffer, W. Pflanzenphysiologie Zweite Auf. Bd. I. p. 548; Bd. II p. 133-134. 



= Czapek, F. Biochemie der Pflanzen 1905 Bd. II, p. 396 and the literature quoted 

 in the above references. 



"Proc. 38th Meeting, 1922 (1923)." 



