THE MANY RESPONSE TYPES 17 



%> (a) Quantitative short-day plants. 



C_) (b) Quantitative long-day plants. 



B. Absolute or qualitative response to day-length (specific 

 day-length required for flowering). 



(a) Short-day plants. 

 O (b) Long-day plants. 

 3. Combination of day-lengths or special day-length required 

 for flowering. 



A. Quantitative response. 



'^y (a) Quantitative intermediate - day plants. Plants 

 flower under all day-lengths but flower best when 

 the day is neither too short nor too long. 



C' (b) Quantitative short-long day plants. Plants flower 

 under all day-lengths but flower best when they 

 are given short days followed by long days. 



CJj (c) Quantitative long-short day plants. Plants flower 

 best when given long days followed by short days. 



B. Absolute or Quahtative response. Plants flower only when 

 they receive a special day-length or combination of day- 

 lengths. 



O (a) Intermediate-day plants. 



O fj [i) (b) Short-long-day plants. 



3 CI CI' (c) Long-short-day plants. 



IL Effects of Temperature on Flowering 



— 1. No effect of temperature on flowering. 



2. Quantitative response. There is no absolute requirement for 

 a specific temperature, but such treatment promotes flowering. 

 This could be subdivided according to whether the response 

 is inductive (delayed) or non-inductive (direct). That is, the 

 particular temperature treatment may not cause any visible 

 change in the plant at the time of the treatment, but subse- 

 quently the plant will flower. Such a response would be 

 considered delayed or inductive. On the other hand, plants 

 are known (e.g. Brussels sprouts) in which the formation of 



