Recent Work with Cuttings 



Potassium permanganate (one ounce to 8 gallons (U.S.) of 

 water) was found superior to any "synthetic" tried, for root- 

 production on kudzu cuttings. (Myers et al., 1938). 



The action of some of the minor elements, such as boron, 

 zinc, and manganese, has been compared to that of vitamins. 

 This is not the place for a discussion of the roles of simple in- 

 organic combinations of elements necessary for plant growth, 

 but one organic compound has a special interest, as it has 

 been claimed to be a succedaneum for inorganic iron. It has, 

 apparently, no special effect in root-induction. 



Iron is usually regarded as essential for plant growth, and 

 it is supposed to have a special part in the formation of 

 chlorophyll, although chlorophyll contains no iron. Pollacci 

 and Oddo (1920) claimed that solution-cultures deprived of 

 iron but supplied with other necessary elements and with 

 magnesium 2-pyrrole-carboxylate, permitted normal growth 

 of several species of plants. The pyrrole ring brings to mind 

 the indole compounds and nicotinic acid ; like inorganic iron, 

 these may be growth-catalysts. 



The work of Pollacci and Oddo was challenged by Deuber 

 (1926) who found none but a toxic effect to be exerted by the 

 pyrrole-carboxylate, even in minimal doses. That the 

 substance had a stimulating effect was reaffirmed by Pollacci 

 and Oddo (1932) for higher plants, and again by Pollacci for 

 algae {Ber. Deut. hot. GeselL, 1935, 53, 540). 



Para-phenylenediamine has been successfully used by 

 Hubert and Rappaport (1939) to stimulate root-formation on 

 cuttings of several species of shrubs. It was used at a concen- 

 tration of loo-iooo mg. per litre, at which strengths its action 

 was reported to be very similar to that of the usual concen- 

 trations of indole-acetic acid. 



Honey has recently been found by R. W. Oliver {Sci. Agric, 

 1939, 19, 586) to exert a considerable stimulating action on 

 the rooting of cuttings of Thuja and chrysanthemum. 



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