THE MANY RESPONSE TYPES 23 



are 777 possible plant response types illustrated by the figure. 

 Interactions which are really different response types are classified 

 together in the present system (long-day at high temperature, day- 

 neutral at low falls in the same category as quantitative long-day at 

 high temperature and day-neutral at low). Thus it would be quite 

 simple to increase the response types beyond 777, but we will leave 

 further complications to the future. 



The classification in the appendix includes mostly plants in the 

 rather readily available literature, mostly the review by Chouard (13) 

 and a list in The Handbook of Biological Data?- Some plants were 

 left off because of lack of information about their response; e.g. the 

 response to cold may be stated, but response to day-length may not. 

 Of those plants which are included, it is quite likely that a majority 

 will prove to be in a wrong category as experimental work progresses. 

 This is most true of the temperature and day-length interaction 

 categories. Very little information was available about these cate- 

 gories, although it is quite likely that most plants would show such 

 an interaction if it were studied. Main changes in the future should 

 be movement of a plant from a no-interaction category to a specific 

 interaction category. The Japanese morning glory is an excellent 

 case in point. During the 1950's it has been studied so intensively by 

 the Japanese that information about it probably equals information 

 about any other plant, and yet it was only in 1961 that its day-neutral 

 response at low temperature was demonstrated. The response is not 

 striking but quite real. Previously this plant was considered to be a 

 typical short-day plant with temperature interactions only in so far 

 as the critical dark period was concerned. Nearly all of the plants in 

 the appendix have been studied only very superficially compared to 

 the Japanese morning glory. The present policy was to place the 

 plant in a "no response" category if in doubt. 



1 The following reviews also contain lists of plants, showing response type: 

 references 17, 24, 25. 



