15 

 plants after foliar application of gibberellic acid. After one week 

 both the fresh and dry weights were significantly higher; however, after 

 two weeks there was no difference between treated and control plants. 



Physiological effects of the gibberellins which account for the 

 change in growth, metabolism, and morphology of plants are as varied 

 and as contradictory as those reported above for the morphological 

 effects. These effects, however, can be grouped into the following 

 categories: cell division; cell elongation; osmotic potential; respira- 

 tion through enzyme metabolism; carbohydrate and lipid metabolism; and 

 changes in membrane permeability. 



The exogenous application of gibberellins has been shown to produce 

 a pronounced increase in cell division in the subapical men stem of 

 Hyoscyamus niger and Samolus parvif Torus (both of which are rosette 

 species), Phaseolus vulgaris (a non-rosette), and various other species 

 (Sachs and Lang, 1957; Weaver, 1972; Shininger, 1974). In a review by 

 Shininger (1974), increased cell division was noted in 13 of 21 species 

 treated with gibberellins. Salisbury and Ross (1978) hypothesized that 

 increased cell division by gibberellins may be caused by an increase in 

 the number of sites on the chromosome where DNA and RNA synthesis can 

 occur by unmasking initiation sites for DNA and RNA synthesis. Nitsan 

 and Lang (1966) demonstrated that elongation of lentil epicotyls in 

 response to gibberellic acid required DNA synthesis. Nakamura and 

 Takahashi (1973) also reported gibberellic acid enhanced DNA synthesis. 

 The response of a given cell to divide or elongate appeared to depend 

 upon its age or stage of development. Younger cells respond by dividing 

 while older cells respond by elongation only (Marth et al . , 1956; Mann, 

 1974; Shininger, 1974). 



