90 



GERMINATION OF SEEDS: SEEDLINGS 



cool, but if Corn or Melons, which have a high temperature re- 

 quirement, are planted before the weather and ground are warm 

 they will decay and have to be replanted. In considering tempera- 

 ture in relation to germination, three temperatures are usually 

 noted; the minimum, the lowest temperature at which germina- 

 tion wiU occur; the optimum, the temperature most favorable 

 for germination; and the maximum, or highest temperature per- 

 mitting germination. As the following table shows, these tem- 

 peratures are very different for different seeds, sometimes differ- 

 ing as much as 25° or 30° (Fahrenheit). 



Germination, which proceeds most rapidly at the optimum 

 temperature, decreases in rate as the temperature approaches 

 the minimum or maximum as the following table shows in 

 case of Corn, in which the time required for the radicle to break 

 through, though only 2 days at the optimum temperature, was 

 10 days in a temperature near the minimum. In the majority of 

 cases, the temperature of the soil in which seeds are planted is 

 somewhat below the optimum and, consequently, if the soil tem- 



EFPECT OF TEMPERATURE ON RATE OF GERMINATION 



