260 Auxins in Agriculture 



modifying floral initiation have been fairly well worked out, the 

 applicability of the information to agricultural crops has been very 

 limited. Attempts to inhibit flowering of some field crops by foliar 

 auxin application have damaged the crops without producing a 

 control of flowering (Rice, 1950). While some control of celery flower- 

 ing has been obtained with auxin, the effects were inconsistent 

 (Wittwer et nl, 1947; Clark and Wittwer, 1949). Evidence of a more 

 complete control with maleic hydrazide has been indicated (Wittwer 

 et al, 1954). An effective inhibition of bolting of sugar beets with 

 auxin has been reported (Price et al, 1950). 



Curiously enough, auxins not only can alter the number of 

 flowers, but they can also alter the sex of flowers. Laibach and Kribben 

 (1950) have reported that auxin treatment of gherkin flowers caused 

 an increase in the number of female flowers and reduction of male 

 flowers. A differential sensitivity of male and female flowers to growth 

 regulators has led to the development of sprays to cause the abortion 

 of male inflorescences. For example, Naylor (1950) and Moore (1950) 

 have successfully used maleic hydrazide to induce male sterility in 

 corn plants, suggesting that the chemical treatment could substitute 

 for detasseling in the production of hybrid corn seed. The technique 

 has been extended to some cucurbits and tomato (Rehm, 1952). 



A promotion of flowering by auxin treatment has been reported 

 by Shigeura (1948) for the litchi tree. This crop is limited in produc- 

 tivity in Hawaii by irregular flowering, a situation which may be 

 alleviated somewhat by auxin sprays. 



SEED TREATMENT WITH AUXIN 



Following the reports by Cholodny (1936) and Thimann and 

 Lane (1938) that short-term auxin treatments of seeds could produce 

 increases in earliness and vigor of grains in a manner suggestive of 

 vernalization (see figure 52, p. 115), many attempts were made to 

 utilize such a treatment to increase earliness of crop plants. Results of 

 such experiments have not generally been promising. A few labora- 

 tories reported gains in flowering (Stier and DuBuy, 1938; Borgstrom, 

 1939; Tang and Loo, 1940), but the great majority of such attempts 

 foinid no consistent beneficial effect (e.g. Barton, 1940; Stewart and 

 Hanuier, 1942). More recently it has been found that differences in 

 temperature experience of soybean seeds following the auxin treatment 

 can result in opposite flowering responses to the treatment. This effect 

 of temperature can be seen in figure 107. The application of auxin- 

 to seeds followed by a period of low temperature incubation can 

 sometimes produce a strong gain in early flowering. Such gains are 



