VL ISOLATION OF CHLOROPLASTS FROM 



LEAF CELLS 



Chloroplastic material was separated from spinach leaves by 

 Chibnall (1924), who ground the leaves in water, removed liquid by 

 squeezing through a silk bag, and filtered the fluid through paper 

 pulp. The chloroplastic material mixed with other cellular constit- 

 uents was retained on the filter. Menke (1937) found that ammo- 

 nium sulfate would precipitate chloroplastic material from an acidi- 

 fied suspension prepared by grinding spinach leaves in water. The 

 most satisfactory preparations are obtained by differential centrifu- 

 gation. This procedure was adopted by IMenke (1938), who employed 

 M/15 phosphate as the suspension medium, Mommaerts (1938) , who 

 used water containing a little calcium carbonate, Granick (1938), 

 who found 0.5 M glucose solution particularly suitable, and Neish 

 (1939) , who also used 0.5 M glucose to obtain intact chloroplasts and 

 distilled water if merely chloroplastic material was desired. Comar 

 (1942), fo.'.nd that freezing decreases the solubility of chloroplastic 

 substance, and he demonstrated that, in a suspension that had been 

 previously frozen, only a few minutes' centrifugation at 3700 R.P.M. 

 was required to bring down the substance. 



The importance, in some cases, of the time of day the leaves are 

 picked was emphasized by Hill and Scarisbrick (1940), who found 

 that if the leaves of Stellaria media were picked at 10:00 A.M. active 

 chloroplasts could be isolated, but if picked later in the day the ac- 

 tivity fell, approaching zero on sunny afternoons. 



The procedures employed by Granick (1938) and Neish (1939) 

 will be described. Galston (1943) showed that Granick's method was 

 applicable to fibrous grass leaves such as those of the oat plant. 

 Neish successfully employed his method with leaves of Trifolium 

 pratense, red clover, Elodea canadensis, and Arctium minus, com- 

 mon burdock, and Onoclea sensibilis, sensitive fern but fibrous or 

 mucilagenous leaves such as those from couch grass or basswood did 

 not yield satisfactory preparations. 



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