106 Plant Tissue Culture 



ml. for each liter of nutrient required. A com- 

 parison of this nutrient with a number of others 

 in common use is given in the accompanying table. 



A convenient experimental series includes 200 

 cultures requiring 10 liters of nutrient. Each cul- 

 ture receives 50 ml. of solution. To prepare 

 nutrient for such a series, 200 g. of sucrose are 

 dissolved in 2 liters of double-distilled water. In 

 1 liter of water are dissolved 25 mg. of Fe 2 (S0 4 ) 3 - 

 These are mixed, 1 liter of stock salt solution and 

 10 ml. of glycine-thiamin solution are added, and 

 the whole is made up to 10 liters. This is then 

 distributed to the culture flasks in 50 ml. aliquots, 

 using a special semi-automatic measuring burette 

 (Fig. 31) which greatly facilitates rapid ma- 

 nipulation. For experimental nutrients (as dis- 

 tinct from stock nutrients) where each liter differs 

 from each other one in constitution, it is best to 

 use graduates instead of burettes for this distri- 

 bution. After all the flasks are correctly charged 

 with nutrient, they are plugged with cheesecloth- 

 covered non-absorbent cotton plugs, capped with 

 inverted 50 ml. beakers, and sterilized. 



Sterilization. Most nutrients used for plant tis- 

 sue cultures contain sucrose and are unaffected by 

 autoclaving. The usual routine is to sterilize for 

 20 minutes at 18-20 lbs. pressure. It has been 

 found convenient to place flasks of nutrient as soon 

 as filled in galvanized iron trays 13" X 21" X 3£". 



