The respiration rate increases during germination, therefore, the medium in which the seeds are placed should be loose and well-aerated. If the oxygen supply during germination is limited or reduced, germination can be severely retarded or inhibited. Heat A favorable temperature is another important requirement of germination. It not only affects the germination percentage but also the rate of germination. Some seeds will germinate over a wide range of temperatures, whereas others require a narrow range.
Many seed have minimum, maximum, and optimum temperatures at which they germinate.
For example, tomato seed has a minimum germination temperature of 50 o F and a maximum temperature of 95 o , but an optimum germination temperature of about 80 o . Where germination temperatures are listed, they are usually the optimum temperatures unless otherwise specified. This often means the germination flats may have to be placed in special chambers or on radiators, heating cables, or heating mats to maintain optimum temperature. The importance of maintaining proper medium temperature to achieve maximum germination percentages cannot be over-emphasized. Germination will begin when certain internal requirements have been met.