150 PLANT GROWTH SUBSTANCES 



the effects of the two compounds were compared. Naphthaleneacetic 

 acid increased starch hydrolysis and the accumulation of sugars. Naph- 

 thaleneacetamide caused the simple forms of carbohydrates to be built 

 into more complex forms, such as lignin and cellulose, as was indicated 

 by microscopic examinations of stem sections (31). Thus two regulators 

 that are closely related chemically brought apparently opposing responses 

 when applied to stem tissues. 



The mineral content of the stem tissues of bean plants has been 

 increased through the apphcation of growth regulators to the stems (8) 

 and to the roots (8,20). The movement of potassium, magnesium, 

 manganese, and boron into treated regions of stems was increased a 

 measurable amount within 30 hours after indoleacetic acid was applied. 

 Phosphorus and copper were mobilized in treated stem tissues within 

 48 hours after treatment. Iron and aluminum were also mobilized by 

 treatment but more slowly than were other elements. The calcium 

 content of stems was not affected by treatment with indoleacetic acid. 



In these experiments a sufficient amount of the regulator was used 

 to bring about cell proliferation. It is obvious that certain elements were 

 used for the structure of these new cells, and some elements, such as 

 phosphorus, were found to increase in the treated stems at a rate about 

 equal to the increase in total solid substance. On the other hand, there 

 is evidence that some metals, such as copper, magnesium, and iron, 

 are essential to enzyme systems, and it is suggested that these elements 

 accumulate in tissues where meristematic activity has been induced, 

 and play a part in the relatively large amount of enzyme activity in- 

 volved (8). It is of interest that calcium, which is not abundant in 

 meristematic tissues, was not mobilized as the result of treatment of 

 stems with indoleacetic acid. 



Recently Rhodes and Templeton (47) reported that 2-methyl-4- 

 chlorophenoxyacetic acid interfered with the potassium metabolism of 

 rape but not of oats. They suggested that this adverse effect on potassium 

 metabolism may account for the herbicidal effects of 2,4-D and for the 

 difference in sensitivity of these 2 kinds of plants to this type of herbicide. 



The effect of 2,4-D and other growth regulators on the composition 

 of fruits has recently received attention. In general, growth regulators 

 tend to hasten starch hydrolysis in the tissues of relatively mature 

 detached fruits like the banana, pear, and apple. With respect to starch 



