Growth form of Linum grandiflorum changed 

 by X-radiation 



Edna L. Johnson 



Plants which exhibit changed growth form in response to 

 X-ray treatment in the seedHng stage vary in the character of 

 the type of branching which occurs. Tomatoes assume a more 

 bushy form because of the greater development of lateral 

 branches. This is true also for certain members of the Pink and 

 Evening primrose families. Other species such as the castor-oil 

 plant and sunflower are prone to show dichotomous branching. 

 Linum grandiflorum and Linaria maroccana when treated in the 

 seedling stage develop, as compared with the controls at ma- 

 turity, a greater number of main branches from the crown; 

 secondary branches at the bases of the main ones also occur in 

 greater abundance. 



Lower portions of plants of Linum grandiflorum, the scarlet flax, to show 

 nature of branching. Above, controls; below, plants whose seedlings had been 

 exposed to one medium dose of X-rays. Note that the main central stalk has, 

 in two plants, been replaced by numerous branches. Greater production of 

 branches by the central stalk of rayed plants was noticeable in two groups of 

 Linum grown to maturity. 



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