Broader Concepts 5 



covered and developed in the past quarter century. Weeds may be re- 

 moved selectively from crops, the dormancy of buds can be prolonged 

 or disrupted, the processes of abscission can be instigated or retarded, 

 and the interconversion of starches and sugars can be directed one way 

 or the other. Frequently the magnitude or even the direction of 

 these interconversions can be regulated very specifically by the dosage 

 applied and the maturity of the tissues at the time of application. 



It is of more than passing interest that a major proportion of the 

 plant regulants discovered to date are organic acids. Many others 

 contain strong electronegative or alcohol, ester, and ether groups that 

 could be converted into carboxyl groups by relatively simple processes 

 of hydrolysis or oxidation. The predominant presence of acidic 

 moieties in the molecule raises serious questions as to the nature of 

 their effect. One soon comes to suspect that they may be primarily 

 involved in altering the nature of cell walls since they present won- 

 derful possibilities for affecting the synthesis of cellulose, lignin, and 

 pectin, the very materials that lead to restriction of cell expansion 

 and define tissue integrity. 



If most of the mechanism of plant regulation by these acidic sub- 

 stances is proven to be associated with cell wall deposition, then it 

 becomes obvious that the science of auxinology is really in a very 

 primitive state. Only the surface of the problem has been scratched, 

 and the really great practical achievement must still be ahead of us. 

 The great potential of the cell lies in the activities of the protoplast 

 and especially in its nucleus rather than in the behavior of the cell 

 membrane and its structural support in the wall. 



Therefore, it is not out of order to propose that attention must 

 be directed to creating chemicals that will penetrate the living cell 

 and enter into the vital processes of the natural cell-regulating sys- 

 tem. A study of the analogues and homologues of nucleic acid com- 

 ponents and those materials that will alter the processes of protein 

 synthesis and activation should in due time provide fruitful leads 

 to new plant regulants. 



Unfortunately this is a complicated area of cell function to attack. 

 However, with the sweeping progress being made today in protein 

 chemistry and the understanding of DNA and RNA synthesis it is 

 not too much to expect that before long we will see chemicals that 

 will generate a directed cytoplasmic structure that will regulate vital 

 processes of metabolism on a more restricted self-sustaining basis. The 

 closest analogy to this material known today is the plant viruses. At 

 least one of these (breaking of tulips) has been associated with pro- 

 duction of a desirable horticultural property. 



