Correlation 99 



Where flowering and fruiting are continuous, as in squashes, if a certain 

 number of fruit are set, related to the food-producing capacity of the 

 plant, the development of more flowers ceases and will not be resumed 

 unless the growing fruits are removed. There is thus a continuous compen- 

 satory balance between the development of multiple plant organs and 

 the amount of material or hormone available for their growth. 



A balance also occurs between the vegetative and the reproductive 

 phases of a plant ( Murneek, 1926 ) . Tomatoes in which fruits are allowed 

 to form abundantly will soon cease vegetative growth, but if flowers and 

 young fruits are continually removed, the plants will grow to a much 

 greater size. A potato plant in which tuber formation is prevented will 

 often bear a large crop of fruits, structures which normally fail to develop 

 presumably because of the diversion of food to the tubers. Mirskaja 

 ( 1926 ) removed all flower buds from plants of a number of species and 

 found that this stimulated formation of lateral shoots and increased the 

 size of leaf blades, tubers, and pith cells and the amount of lignified 

 tissue. 



Removing the axillary buds from Coleus plants was found by Jacobs 

 and Bullwinkel (1953) to induce longer stems, larger leaves, and more 

 rapid growth of the main shoot ( Fig. 5-1 ) . The ancient art of topiary is 

 simply a manipulation of these compensatory correlations. The removal 

 of certain buds stimulates the growth of others which would have re- 

 mained dormant, and by this means the form of the plant can be 

 altered. 



Such correlations may perhaps be called competitive rather than com- 

 pensatory. In certain hybrid cherries, for example, the embryos start their 

 development but when partly grown they shrivel and die. Tukey (1933) 

 and others were able to bring such embryos to normal maturity by re- 

 moving them from the seed and growing them in culture. In normal plants 

 the embryo may be thought of as competing successfully with maternal 

 tissues for food during development, but in these unusual cases most of 

 the food is drawn instead to maternal tissues, and the embryo dies. Re- 

 lease from such maternal competition allows it to grow. 



Compensatory correlations are also to be observed in the development 

 of individual organs. MacDougal (1903k), who has reviewed the early 

 literature, described many examples of this, as did Goebel and others. In 

 some plants, for example, if the blade is removed from the young and 

 growing leaf, the stipules will become much enlarged. The building ma- 

 terial available to the leaf is employed in its growth but the distribution 

 of this material is not the usual one. 



A good instance of compensation is reported by Johnston ( 1937 ) be- 

 tween the coleoptile and the first internode of Avena. Light stimulates 

 the growth of the former but depresses the latter. Regardless of light, the 



