286 CORN CROPS 



PHYSIOLOGY OF THE SOKGHUMS 



213. In general, the physiology and nutrition of sor- 

 ghum are similar to those of corn, which has been set forth 

 (page 38). The most interesting physical phenomenon of 

 sorghum from an economic standpoint is its general re- 

 sistance to drought and to the climatic conditions that 

 prevail in dry climates. 



Drought resistance. — The drought resistance of sor- 

 ghum is well established. Its ability to yield in a dry 

 chmate is apparently not due to a deep root system or to 

 any other adaptation of the root system so far reported. 

 Neither does it seem to be due to a low water requirement, 

 as the few tests made on this point indicate that quite as 

 much is required per pound of dry weight as for Indian 

 corn or for other crops not particularly adapted to dry 

 conditions. 



The success of sorghum, under semiarid conditions 

 seems to depend on two qualities, not found developed 

 to so great a degree in other crops : (1) The high resist- 

 ance of leaves to injury from hot, dry weather. The non- 

 saccharine groups, especially, will withstand dry and hot 

 climatic conditions that would wither most vegetation be- 

 yond recovery. (2) The plants have the faculty of becom- 

 ing almost dormant, so far as growth is concerned, for 

 long periods during severe drought. During such periods 

 the leaves roll and tend to assume an upright position. 

 This, no doubt, reduces evaporation from the leaves and 

 affords protection to the younger leaves and the seed 

 head. The plant may remain in this condition, apparently 

 without growth, for several weeks, far beyond the endur- 

 ance of most cultivated plants. With the coming of rain, 

 growth will usually be renewed with vigor. If the main 



