2 TRANSLOCATION IN PLANTS 



its photosynthetic organs at a distance of from 10 to 100 

 or more meters from its mutually interdependent salt- or 

 water-absorbing organs, it becomes imperative that some 

 effective transportive system be at hand. An effective 

 solute-transporting system is essential even for the develop- 

 ment of the smaller herbaceous plants where distances 

 between organs do not exceed a few centimeters or deci- 

 meters. In fact but few of the plants that now exist, 

 except the unicellular and some of the filamentous forms, 

 could have developed or could continue to exist if they 

 had not developed and maintained an effective transport 

 system. 



It is evident that no one cell or tissue of a higher plant is 

 self-sufficient, and that conditions determining the move- 

 ment of materials from one region to another may pro- 

 foundly influence the behavior of these different cells and 

 tissues, and therefore the plant as a whole. For example, 

 the behavior of a plant may be largely determined by what 

 eventually becomes of the carbohydrates manufactured in 

 a leaf; that is, whether they stay in the leaf, are carried to 

 the apical shoot meristem or to the axillary meristems, or 

 are carried to the stem cambium, the root apex, the root 

 cambium, or to a storage organ, or to fruits. In a similar 

 way the distribution of the materials, such as water and 

 various salts or ions absorbed by the roots, may profoundly 

 influence behavior. 



Of the immense number of actual or potential growing 

 points, as in that part of a tree which is above ground, 

 only a few ever grow under what we call '"'normal" condi- 

 tions. Yet in most plants any bud, except perhaps the 

 flower bud, is capable of producing a shoot, and in many 

 kinds of plants almost any meristematic cell is capable of 

 producing either a shoot or a root. Though some investi- 

 gators think that normal behavior as regards growth corre- 

 lations is controlled largely through the transmission of 

 influences or stimuh, it is equally possible that normal 

 behavior is controlled largely through ''normal" distribu- 

 tion of materials. By upsetting this distribution of mate- 



