ALDEHYDES, NUCLEIC ACIDS, AND PLASMAL 67 



The use of ultraviolet absorption for the localization of nucleic 

 acids is discussed on page 113. 



Coleman Preparation of Feulgen Reagent 



Dissolve 1 g. basic fuchsin in 200 ml. boiling water; filter, cool, and 

 add 2 g. potassium metabisulfite (K2S2O5) and 10 ml. 1 N hydro- 

 chloric aci^. Let bleach for 24 hr., and then add 0.5 g. activated car- 

 bon (Norit), shake for about 1 min., and filter through coarse paper. 

 The filtrate should be colorless. 



Whitaker Feulgen Technique for Plant Tissues 



SPECIAL REAGENTS 



Modified Brenda Fixative. Combine 30 ml. 1% chromic acid with 



10 cc. 2% osmic acid. 

 1 N Hydrochloric Acid. 

 Feulgen Reagent. See above. 

 45% Acetic Acid. 



PROCEDURE 



1. Fix tissue in the modified Brenda fluid for a period depending 

 on the specimen, e.g., 15-20 min. for root tips, 30-45 min. for whole 

 anthers. 



2. Hydrolyze in 1 .V hydrochloric acid at 50-60° for the same 

 time used in fixation. 



3. Place in stain for 15-20 min. and then transfer to 45% acetic 

 acid for 10-15 min. or longer. 



4. Put specimen in a drop of 45% acetic acid on a glass slide and 

 perform any dissections at this stage. 



5. Place cover slip over the material and heat the slide nearly to 

 boiling at least three times. Apply pressure to cover slip with each 

 heating to make the tissue adhere to the slide. 



6. Float off the cover slip in a mixture of equal vol. absolute 

 alcohol and glacial acetic acid. 



7. Transfer to 95% alcohol for at least 15 min. and mount in 

 euperal. The mounting must be done in low humidity and care must 

 be taken to avoid breathing on the slide since moisture results in 

 cloudiness. The mounted material keeps well permanently. 



Result. A positive reaction is indicated by a purple color. 



