388 



GROWTH FACTORS AND FLOWERING 



might be studied as to their effect upon the morphological development 

 of floral primordia. The auxins might be studied to see if their effect is 

 upon translocation of flowering stimulus or some other process such as 

 destruction of flowering hormone in the leaf. A start has been made 

 with the auxins as shown in Fig. 4. Plants treated with auxin just fol- 



5.0-- 



4.0-- 



ui 

 u 



v» 



< 

 o2.0-- 



1.0- • 



Control 



• No ouxin 



Auxin Control - 



o o- 



o 3 X 10*'' M NAA 



noon midnight noon midnight 



TIME AFTER INDUCTION (16 hr dork period) 



Fig. 4. The effect of naphthaleneacetic acid upon translocation of 

 flowering hormone. Plants defoliated at various times following a single 

 16-hr inductive dark period, which was begun on July 30, 1957. Ten 

 plants per treatment, buds examined after 9 days. Plants in this and sub- 

 sequent figures were prepared as previously explained (Salisbury, 1957b). 



lowing a single dark period were defoliated at various times. It is 

 evident from the figure that the time relations of flowering hormone 

 translocation are not influenced by auxin. 



Dinitrophenol is being investigated further at Colorado State Uni- 

 versity to relate certain herbicidal effects of this compound to the 

 effects upon flowering (Salisbury, 1957a). It is important to note that 

 dinitrophenol wiU inhibit hormone synthesis but that it does not ex- 

 tend the critical night. This, along with other evidence (Salisbury and 

 Bonner, 1956), would seem to separate these two reactions. 



Since cobaltous ion influences the critical night (SaHsbury, 1957a, 

 b), it seemed pertinent to see whether this ion changed the amount of 

 photoreceptor pigment or affected the preparatory reaction. Some idea 

 of the amount of photoreceptor pigment present in the plant can be 

 obtained by determining the amount of light required to saturate the 

 photoreaction. This is done by exposing plants to various durations of 



