86 Colchicine 



c-pairs. Polar groupings of c-pairs typily the distributed metaphase. 

 whereas exploded metaphases are nonpolar. Unquestionably, the 

 distributed c-metaphase was clearly illustrated in pollen tubes.'^^ The 

 distributions were equal and unequal. They were not conceived as a 

 somatic meiosis. In root tips, naphthalene acetic acid and colchicine 

 increased the number of distributed c-mitoses compared with either 

 chemical alone. Other chemicals increase this type even more than 

 colchicine. 



3.6: Spindle Disturbance and Cytological Standards 



Spindle disturbances in plants may be classified in three cate- 

 gories:"'^ (1) full inactivation, stathmokinesis,-^ (2) partial inacti- 

 vation, merostathmokinesis,-^'^ (3) slight disturbance in orientation, 

 tropokinesis.^^' -^ All these types are produced by colchicine, as al- 

 ready pointed out. If one wishes to make comparative studies with 

 other chemicals known to influence mitosis, well-defined cytological 

 standards of judgment are needed to classify reactions as either dis- 

 turbed or normal. If the reaction is disturbed, it is important to dis- 

 tinguish the type according to velocity or strength of reaction. The 

 most reliable criteria appear to be those based upon tests at telophase, 

 rather than at earlier stages.'^-^ 



Abnormal chromosomal distributions may be caused l)y spindle 

 disturbances in three degrees: first, multipolar; second, ajjolar: and 

 third, luiipolar. When three or more groujjs of chromosomes join so 

 as to form discrete groups, partial spindle disturbances are obvious. 

 These were carefully noted under the general type, mcrostathmoki- 

 nesis,-^*^ or under the present classification as midtij^olars. Howe\er, 

 complete destruction or inactivation lea\es one single grouj), or there 

 may be two groups with no e\idence of spindle function. This is the 

 apolar distribution. Another specialized distiubance is the close gather- 

 ing at one focal point described before as the star metaphase; this type 

 becomes unipolar at telophase.'-^ 



Colchicine (().0{)5 per cent) a]jplied to Allium root tips for 46 hours, 

 increases the percentage of trojjokineses. Ihe controls may show as 

 many as 10.5 per cent, but treated root tips raised the frequency to 

 21.3 per cent. These disturbances are the first-order changes occurring 

 at threshold concentration,-^ and are the first signs of spindle dis- 

 turbance. 



3.7: Cytoplasmic Division 



Nuclear mitosis and the completed process of cell division are not 

 synonymous, because the nuclear processes and cytoplasmic processes 

 taken together make up cell di\ision. Truly, karyokinesis (nuclear 

 mitosis) and cytokinesis (cytoplasmic processes) are very highly intc- 



