6i8 GROWTH CORRELATIONS 



continued to grow vegetatively. If, however, the fruits were allowed to 

 remain on the plant and enlarge, vegetative development and the production 

 of flowers gradually slowed down as more and more fruits began to develop. 

 The steps in the inhibition of the development of such plants proceeded in 

 approximately the following order: (i) loss of fecundity by the blossoms, 

 (2) decrease in the size of the floral clusters, (3) abscission of the flower 

 buds, (4) checking and later cessation of terminal growth of the stem and 

 (5) eventual death of all parts of the plant except the fruit. 



The checking effect of the enlargement of fruits upon continued vegetative 

 development and the development of flowers resulted, according to this m- 

 vestigator, from the virtually complete monopolization of all of the nitrogen 

 in the plants by the fruits. Carbohydrates, on the other hand, were found 

 to be stored in considerable quantities in both the fruits and vegetative organs. 

 In general, the more nitrogenous compounds available the more fruits that 

 set and started to develop before inhibition of flowering and vegetative growth 

 began. Removal of the fruits at any tim.e before the vegetative parts died 

 resulted in a renewal of vegetative growth, and, ultimately, in another cycle 

 of reproductive development. 



Development of flowers often has a checking effect on vegetative growth, 

 while at a later stage in the life history of the same plant, fruiting may 

 inhibit both further flowering and vegetative growth. This type of correlative 

 development is shown by cotton plants (Pearsall, 1923) and many other 

 species. 



Correlative effects between fruiting and flowering can be observed in most 

 species which develop flower primordia over a considerable period of time, as 

 is true of many summer-blooming species. If the blossoms of the sweet pea 

 {Lathy rus odoratiis) are allowed to develop, for example, flowering soon 

 ceases, but if they are picked from time to time flower primordia and blossoms 

 are produced continually throughout the growing season. All experienced 

 flower gardeners know that if continued flowering is to be maintained in many 

 species, especially annuals, that the flowers must be cut as rapidly as they 

 open, and that allowing fruit development to proceed soon results in a checking 

 or even complete cessation of flowering. 



It is usually considered that all of the growth correlations just described 

 can be explained in terms of the internal food relations of plants. In gen- 

 eral, they are believed to result from a diversion of such a large proportion of 

 the available foods to developing flowers or fruits that other organs suffer a 

 deficiency and hence are checked in growth. Both developing flowers and 

 fruits are organs of high assimilatory and respiratory activity and hence their 

 maturation may result in a considerable drain on the available food supply. 



