348 Colchicine 



eration ot vegetative propagation in spite of well planned and care- 

 fully followed methods of determining numbers of chromosomes. 

 These seven generations were preceded by four vegetative generations 

 in which two were selected after chromosomes were determined to 

 guide the selection. 



In some cases individual anthers yielded diploid and tetraploid 

 microspore mother cells.-" Clearly a mixoploid tissue gave rise to 

 these anthers. Remembering that tested plants were remo\ed from 

 the tetraploid progenitors by several generations of propagation, the 

 persistence of diploid and tetraploid cells with neither one crowding 

 out the other is of particular interest. Liliinn is considered to be 

 tetraploid on the basis of chromosome counts; yet diploid and tetra- 

 ploid pollen mother cells have been found in the same anther of 

 lilies.-" In one test a generation was grown by scale propagation and 

 ten plants were selected. One plant from scale propagation and three 

 plants obtained by dividing the original bulb yielded flowers with 

 anthers that had both dij^loid and tetraploid cells. The parent plant 

 was supposedly a tetraploid. 



Both cases mentioned here, Li Hum and LoUuui. represent vegeta- 

 tive propagations, and in each instance colchicine created a mixo- 

 ploid tissue. Projects that involve vegetative increase present complex 

 problems, the true nature of which remains unsolved. 



14.3: Chimeras Induced by Colchicine 



In longitudinal section, the apical meristem of Vinca rosea L. 

 shows a distinct la\ering of cells. '^ These are clearly illustrated with 

 the photomicrograph in Figure 14.1, A and B. Using terminology 

 promoted by plant anatomists, the first layer is called T^ and the next 

 To. These, then, refer to the first and second layers of a tunica. The 

 third layer and cells deeper in the apex are called the corpus, initialed 

 C'l and C.J. Lower than C., no specific layers can be observed. ^^ 



From species to species the limits of the tunica and corpus may 

 vary. For example, J'ijica minor L., obviously related to V. rosea, was 

 described with three layers of tunica and a fourth as the corpus. If 

 the older terminology of Hanstein is related to the tunica-corpus 

 concept using Vinai )nin()r as an example, then T, is ecjuivalent to 

 Hanstein's dermatogen, r._, and T->, are the same as periblem, and Cj 

 is the plerome. Another and different labeling has been used in re- 

 cent cyto-chimeral studies following j^olyploidy induced by colchicine. 

 The layers are called L-I, L-II, and L-III, etc. without reference to a 

 tunica and corpus. ^^ 



The point to be strongly emphasized here is not the terminology 

 but the fact that the various layers make a definite and precise con- 

 tribution to the shoot axis and to such parts of shoot as the flower 



