20 THE FLOWERING PROCESS 



B. Most qualitative or absolute requirement at high tempera- 

 ture. 

 %^r^ (a) Low temperature: quantitative. 



CO 



^"^j (b) Low temperature: day-neutral. 



•o 



C}% (c) Low temperature: response changes. If the 

 '®0 response is absolute at both high and low tem- 



perature, this category would be the same as 

 in.LA.c above, but it is conceivable that a 

 plant might have an absolute requirement for 

 short-days (or long-days) at high temperature 

 and a qualitative response to 1 ong-days (or short- 

 days) at low temperature. 



A change in day-length response type due to temperature 

 treatment. 



eg ^ A. Day-length and temperature treatment are inter- 

 changeable ; that is, the plant will flower in response 

 to one or the other. In the known cases low tem- 

 peratures are required for this effect. Thus we have 

 an interchangeability between photoperiodism and 

 vernaUzation. If flowering occurs while plants are 

 in the low temperature conditions, this becomes 

 category III.2.B.b above. Here there is a day-length 

 requirement unless the plants are made day-neutral 

 with a low temperature treatment. 



e9*|# B. Temperature treatment inductively changes the 

 day-length response type. In the very few examples 

 at hand this is again a low-temperature response. 

 Care must be taken here to separate this response 

 from the ones listed under III.2 above. For 

 example, if a plant requires short-days at low tem- 

 perature, but at high temperature it has no day- 

 length requirement, it would be placed in III.2. A.b 

 above and not in this category. This category is 

 reserved for the inductive response in which plants 



