278 Plant Physiology 



potato leaves and dry in the same manner. These will yield 

 diastase of translocation (ungerminated seeds of barley likewise). 

 Grind the products separately (also powder the leaves) and ex- 

 tract for 24 hours with two times the weight of 20 per cent alco- 

 hol. Filter the alcoholic extract and precipitate the crude 

 diastase (along with some other proteins) by adding 2| parts 

 or more of 95 per cent alcohol. After a short time filter to collect 

 the precipitate. Dissolve the first (from barley seed) in 50 cc. 

 of water, and the second (from leaves) in 25 cc., adding to the 

 first 2 cc. chloroform, and to the latter 1 cc., to inhibit the 

 growth of bacteria. 



Make about 200 cc. of 1 per cent starch paste (from rice 

 starch), and into each of three test-tubes pour 25 cc. of the 

 starch paste, labeling the tubes, A, B, and C. 



To tube A add 5 cc. secretion diastase. 



To tube B add 5 cc. translocation diastase. 



To tube C add 5 cc. distilled water. 



At intervals of \ hour shake the tube, take 1 cc. samples, and 

 test with iodine, noting the changes of color (as dextrins are 

 produced) from blue through purple to wine-red, finally colorless. 

 When the starch reaction has disappeared, note the change in 

 appearance of the solution. Test with Fehling's solution for 

 reducing sugar. 



Drop a small quantity of potato starch into a few cubic centi- 

 meters of each of the two diastase solutions (translocation and 

 secretion) in two vials, slightly acidulate with weak HC1, and 

 after intervals of an hour or so study the types of corrosion. 



If time permits, compare the effects of high and low tempera- 

 ture, bright and reduced light, and strong and weak acids upon 

 diastatic action. 



Translocation. - - Verify the previous indications respecting 

 the use of starch by the leaf or loss from the leaf when placed in 

 the dark. Employing a Fuchsia (as previously used, page 223), 

 geranium, or nasturtium, secure a plant which has been exposed 

 to bright light three hours or more, so that abundant starch occurs 

 in the leaves. Select two or three healthy leaves and on one 

 side of the midrib, or middle, of each sever completely the main 



