Dormancy and Storage 271 



Tentative reports ot success witli maleic hydrazide to prolong dor- 

 mancy of woody plants in storage have also been made (Fillmore, 

 1950). 



Attempts to prolong dormancy of fruit trees in the field have 

 generally involved using salts of naphthaleneacetic acid, either during 

 the previous growing season (Hitchcock and Zimmerman, 1943) or 

 shortly before growth would be expected to begin (McCartney, 1948). 

 Although only one auxin has been tested, the results do not appear 

 to be very promising. 



Attempts to prolong dormancy of sweet potatoes in storage or of 

 some shrubs and trees have been unsuccessful (Simons and Scott, 1952; 

 McCartney, 1948; Way and Maki, 1946). 



Factors in Success 



Since buds can be either stimulated or inhibited in growth by 

 auxins, it is not surprising that attempts to use auxins to prevent bud 

 growth are not always effective. From the experimental data which 

 have been accumulated it would seem that two types of difficulties may 

 be involved, one being to achieve the penetration of the auxin to the 

 growing point in sufficient quantities to inhibit bud growth, and the 

 second being to maintain a sufficiently high auxin level over a period 

 of time to sustain that inhibition. Treatment of dormant materials 

 with esterified auxins probably owes its success to the ability of esters 

 to penetrate the buds more readily and to continue penetration over 

 a long period of time. There are many instances in the literature which 

 demonstrate that inhibitory auxin levels maintained for only a short 

 time can actually result in a stimulatory aftereffect. A clear example 

 of this is reported by Skoog (1939). Consequently, if applied auxins 

 are destroyed in the dormant buds, and are not continuously re- 

 newed, they may produce stimulatory aftereffects. 



Aside from the factors of penetration and maintenance of high 

 auxin levels in the bud, effective prevention of sprouting shows a 

 strong interaction between auxin concentration and temperature. A 

 striking example of this can be seen in figure 113, where sprouting of 

 rose bushes was effectively prevented by the auxins at higher tempera- 

 tures but the inhibition was largely lost at lower temperatures. The 

 control of sprouting of potatoes does not show as clear a temperature 

 interaction, but there are several instances reported in the literature 

 which suggest less effective control at lower temperatures (for example, 

 see figure 109). As already mentioned, maleic hydrazide seems to be 

 more effective at lower temperatures (Paterson et al, 1952). 



The importance of penetration of the applied auxin into the 



