PLANT-TISSUE CULTUEES 



By RoBEBT L. Weintbatjb 

 Division of Radiation and Organisms, Smithsonian Institution 



[With 3 plates] 



The living plant may be likened to a great factory in which a 

 large number of physical and chemical operations are proceeding 

 simultaneously. In the plant, to an extent even greater than in the 

 factory, each of these processes may be affected by any or all of the 

 others and may, in turn, exert an influence upon them. All the living 

 parts of the plant respire continuously, day and night, absorbing 

 oxygen from the air, burning a portion of the living substance or 

 stored material, and excreting carbon dioxide. From the soil the 

 roots absorb water and minerals which are then moved into the 

 aerial portions. In the light the green tissues manufacture carbohy- 

 drates which are supplied to all the rest of the plant and which are 

 transformed into building materials such as cellulose and proteins 

 and into storage reserves such as starch and fat. Many of these pro- 

 cesses, furthermore, are markedly influenced by environmental fac- 

 tors such as temperature of the air and soil, humidity, and com- 

 position of the atmosphere, illumination, and supply of water and 

 minerals. The particular set of environmental conditions which is 

 most favorable for a given physiological function is not necessarily 

 the best for any other process. 



Such a bewildering intricacy renders very difficult the task of the 

 plant physiologist who seeks to gain an understanding of the nature 

 of the various life processes and the interrelationships that exist 

 among them. If it were possible to separate mechanically the in- 

 dividual tissues and organs of the plant and to maintain them under 

 known and controllable conditions while they continued their normal 

 activities, an important advance toward an analysis of the problem 

 would have been achieved. This was first clearly recognized by the 

 German botanist Haberlandt, who wrote in 1902 : 



So far as I know, there has been, up to the present, no well-planned attempt 

 to cultivate the isolated vegetative cells of higher plants in suitable nutrients. 

 Yet the results of such cultures should throw many interesting sidelights on 

 the peculiarities and capacities of the cell as an elementary organism; they 

 should bring into evidence the reciprocal relationships and many-sided in- 

 fluences to which the individual cells of a multicellular organism are subjected. 



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