DORMANCY IN BUDS 



235 



tubers treated with ethylene chlorhydrin or thiocyanates only one bud 

 generally grows from one apical eye of the seed piece. Thiourea may force 

 the growth of all the bud primordia in an eye. This may be as high as 

 eight. Fig. 87 shows the effectiveness of thiourea ^ in inducing the growth 

 of several buds from a single potato eye. Fig. 88 indicates the effect of 

 thiourea in breaking up the correlation between the several eyes of the 



Figure 88. Seed pieces of non-dormant Early Ohio potato. Top row: soaked in 2 per 

 cent thiourea one hour before planting. Bottom row: soaked in water one hour before 

 planting. Note that thiourea forced the growth of buds from eyes throughout the length of 

 the seed piece and that water induced growth of only one bud from an eye at the seed end. 



potato, so that eyes all along the seed piece from the seed end to the stem 

 end produce multiple sprouts. We have noted above that reduced oxygen 

 pressures '^^ had similar effects on eye and bud correlations in potato tubers. 

 In western Nebraska and in Colorado the potato tubers grow too large for 

 economical use as seed. Treating the seed pieces with the proper dosage 

 of thiourea gives more than one stem from the seed piece wath a correspond- 

 ingly greater number of smaller tubers per hill, but with the same yield 

 per acre. In this way treatment of tubers with thiourea has proved of 

 service to seed-potato growers. 



Thiourea as an antioxidant. Denny observed that the cut surfaces of 

 seed pieces of potatoes treated with thiourea remained white for a long 

 time after they were planted, whereas cut surfaces of seed pieces treated 

 with other bud-forcing chemicals, or not treated, turned bro^vn very 

 readily. A further study showed that thiourea interfered with the oxida- 

 tion system in the tuber that produced browTiing. Denny i^- ^o. 24 concluded 

 that it was the peroxide in the system that was inactivated or destroyed 



