Synthetic Qrowth'Suhstances in Qrafting 



strawberry by the use of synthetic growth-substances, the 

 results with holly being thought to be of practical value to the 

 florist. See also Nixon and Gardner (1939). 



In a preliminary report, Bennett and Skoog (1938) give the 

 results of applying yeast extracts and solutions of vitamin Bj, 

 indole-acetic acid, and other substances to the cut tips of dis- 

 budded fruit trees kept in a warm greenhouse. The point 

 about the greenhouse being warm is that cold is normally 

 essential for the breaking of dormancy of fruit trees, just as 

 subjection to a low temperature is an essential feature of the 

 process of vernalization, which is used to "break dormancy" 

 (induce earlier growth) in such seeds as those of winter wheat. 



In these experiments of Bennett and Skoog the effect of the 

 applied substances was not uniformly well marked. Vitamin 

 Bj, while not notably influencing the number of buds pro- 

 duced, appeared to induce strong growth of such buds as did 

 develop. The best effect was obtained by "injection" of 

 extracts of autolyzed yeasts (brewers' and bakers'), especially 

 in young Bartlett pear trees. 



The following is a translation of the summary of a paper by 

 Amlong and Naundorf (1938), after Horticultural Abstracts:^ 



"Coating the dormant buds of lilac (variety, Charles X) once 

 a day for seven days in succession with a hundredth- or 

 thousandth-normal solution of indole-acetic acid, or with a 

 thousandth-normal solution of a-naphthyl-acetic acid, or with 

 certain other stimulating mixtures, results in a considerably 

 earlier bloom. Covering the terminal buds with growth- 

 substance pastes has a similar effect. The forcing effect of a 

 hot-water bath can be increased by spraying the treated plant 

 with indole-acetic acid solution once a day for a week."^ 



^B.C.A. quotes what is apparently the same paper but gives elder as the 

 experimental plant. 



*A "normal solution", sometimes written N solution, is a chemical term 

 here denoting the molecular weight, in grams, of a growth-substance theoret- 

 ically dissolved in a litre of water. The molecular weight of indole-acetic 

 acid is about 170 ; that of the naphthyl acids and the other indole acids which 

 are used as growth-substances is rather more. There is, however, some per- 

 missible latitude in the strength of solutions, and for horticultural purposes 

 no harm will be done if the molecular weight of all these substances is taken 

 as 200. A hundredth-normal solution of indole-acetic acid would be pro- 

 hibitively expensive, as it would contain (nearly) two grams in about a 



55 



