SECTION THREE 



TETRAZOLIUM SALT 



For testing the viability of seeds 



Solution required: 

 A. Tetrazolium salt i% aqueous. 



Technique: 



1. Select the seeds at random and steep in tap water for i8 

 hours. 



2. Section longitudinally through the embryo and place one 

 half of each in a 7 cm. petri dish. 



3. Pour the tetrazolium salt solution over the seeds and soak in 

 the dark for 4 hours at 20° C. 



4. Wash with tap water. 



5. Examine seeds for staining. 



Results: 



Viable seeds are stained: others unstained. 



Note: The method is not well adapted to certain seeds. 



Reference: Cottrell, Helen J. (1948), Ann. Appl. Biol., 35, 123-31. 



THIONIN - ORANGE G 

 For infected plant tissues 



Solutions required: 



A. Carbol thionin. 



B. Orange G 0-2% in absolute alcohol. 



Technique: 



1. Fix paraffin sections to slides; pass through xylol and 

 descending grades of alcohol down to distilled water in the usual 

 manner. 



2. Stain for an hour in the thionin solution. Alternatively, free- 

 hand sections may be employed, in which case, the sections should 

 be stained in the thionin for only five minutes. 



3. Pour off excess stain, and rinse with 70% alcohol followed 

 by 90%. 



4. Rinse quickly in two changes of absolute alcohol. 



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