SECRETARY'S REPORT 135 



of all wavebands employed. Anthocyanin synthesis was maximal in 

 the red, which was from ten to one hundred times as efficient as the 

 blue. At 10 -6 microwatts per square centimeter, the anthocyanin 

 content of plants grown with the red was doubled as compared to 

 that of those in complete darkness. In the far red, where no photo- 

 synthesis could have occurred because of the absence of chlorophyll, 

 the anthocyanin increased eighteen times with the 710-1100 m/x region 

 and ten with the 725-1100 m/x, region at the 10-microwatt energy level. 

 This appears to be strong evidence that, contrary to previous theories, 

 the light effect on anthocyanin synthesis is only indirectly related 

 to photosynthesis and that anthocyanin synthesis can be the conse- 

 quence of an independent photochemical reaction. 



A second phase of the research has been concerned with the effect 

 of growth regulators on the uptake of various nutrient salts by bean 

 seedlings. It was reported previously that the nitrates, chlorides, 

 and sulfates of potassium, calcium, and magnesium were absorbed 

 less rapidly by plants treated with 10 y of ammonium 2,4-D on the 

 leaf or bud than by untreated plants. The reduction in uptake occurs 

 within 24 to 48 hours after the application of the growth regulator as 

 measured by a continuously recording electronic conductance bridge. 

 These reduced uptake patterns appear to be chiefly related to decreased 

 growth of the plants treated with the growth regulator. Unlike the 

 other nutrient salts tested potassium acid phosphate, while eventually 

 absorbed less rapidly when 2,4-D is used, is taken up by the treated 

 plants at an increased rate for a short period beginning about 6 hours 

 from the time of application of the regulator. Other work has indi- 

 cated that about 6 hours is approximately the length of time required 

 for the ammonium 2,4-D to reach the roots of bean seedlings. This 

 increased rate of absorption has not as yet been correlated with any 

 change in metabolism of the seedling. 



Respectfully submitted. 



L. B. Aldrich, Director. 



Dr. A. Wetmore, 



Secretary, Smithsonian Institution. 



236G39— 53 10 



