GROWTH REGULATION 285 



stimulator onto or into the cutting. While any of these are satisfactory, 

 those ^vhich are most convenient include the application of powder 

 mixtures to the bases of cuttings, quick dipping of the bases into con- 

 centrated solutions, and prolonged soaking of the bases in dilute 

 aqueous solutions. Each of these methods has certain advantages and 

 disadvantages, and no single method of application has clear supe- 

 riority over the others. Some plants respond better to one method 

 than to another. 



A number of conditioning factors play an important role in the 

 response of a cutting to the administration of a rooting hormone. 

 For example, it is possible that a deficiency of food materials might 

 become a limiting factor in the production of roots on a fresh 

 cutting. For this reason, sucrose is generally incorporated in the dilute 

 aqueous solutions of the growth regulators. The addition of sugar 

 is quite helpful with difficult cuttings and increases the root mass on 

 most cuttings. When sugar is used in the rooting solution, care 

 should be taken to wash the excess sugar solution from the surface 

 of the cutting in order to reduce the possibility of fungal growth. 



Substances containing nitrogen, for example amino acids, ammo- 

 nium sulfate, and the like, often are beneficial additions to the rooting 

 solution. They are particularly useful in instances where cuttings 

 produce roots only with great difficulty. 



Like the nitrogen compounds, certain vitamins are thought to aid 

 root formation. Favorable responses have been observed when thi- 

 amine, nicotinic acid, and ascorbic acid have been added to the root 

 growth-regulator solution. 



Inhibition of Sprouting 



Each year the loss of millions of bushels of potatoes, carrots, beets, 

 turnips, and onions from sprouting during storage is of significant 

 economic importance. Although mtich sprouting can be controlled by 

 low-temperature storage (below 40°F.), such storage is expensive, and, 

 if accomplished, the end results are not always the most desirable. 

 For example, potato storage at temperatures lower than 40°F. results 

 in an accumulation of reducing sugars such as glucose. To the manu- 

 facturer of potato chips and dehydrated potatoes this is undesirable, 

 since these sugars are partially responsible for an undesirable brown- 

 ing of potato chips and an objectionable discoloration of dehydrated 

 potatoes. 



Although sprouting of potatoes soaked in a solution of 3-indoleacetic 

 acid is somewhat suppressed, the use of this chemical is not very 

 feasible owing to the fact that its entry into a whole, uninjured tuber 



