84 



THE FLOWERING PROCESS 



Table 5-2. Dilution Procedure for Logarithmic 

 Concentration Series 



^ Although 4-place figures are given, 3-place accuracy is usually sufficient (e.g. 

 graduated cylinders may be used). Of course, the greater the number of 

 dilutions in the series, the more the errors could multiply. 



2 Dilutions could be continued indefinitely. 



3 This series was used to obtain the results of Fig. 5-7. Note that concentrations 

 appear at equal intervals on a logarithmic scale. 



allowed to drip off), and problems of contaminating the atmosphere 

 and surroundings are not so great. 



There are many other special ways of applying solutions. To try 

 to pinpoint the time of penetration of a chemical into the leaf, I have 

 dipped the leaves in rather concentrated solutions and then washed 

 them with distilled water after a measured interval of time. With a 

 5 min interval between dipping and washing, approximately 10 times 

 the concentration was required for a given effectiveness as for dipping 

 without washing. 



Some chemicals are taken up by roots and not by leaves and must 

 be applied to the soil. Cuttings of the plant may be placed in test 

 tubes containing the solution, or the leaf blade may be removed and 

 the cut end of the petiole allowed to absorb the solution from a small 

 vial. In studies involving radioactive compounds, a single drop of 

 solution may be placed on the leaf blade. In another approach, the 

 leaf was immersed in a solution during an entire dark period, 

 demonstrating that very low concentrations of certain chemicals (the 

 auxins) would effectively inhibit flowering. These are cumbersome 



