Previous seed crop nutrition was shown to affect 1 - The eye number/tuber weight relationship of the seed tuber 2 - The tine before sprouts appeared on the seed tuber 3 - The proportion of eyes which produced visible sprouts 4 - The pattern of sprout growth in store 5 - The tuber yield produced in the field The eye number of tubers of a given weight was shown to be inversely related to tuber K and the rate of increase of eye number with tuber weight was inversely related to tuber N. A tuber dormancy bioassay was developed which showed that the tubers contained two acid inhibitors which were active in delaying sprouting. The level of the one assumed to be abscisic acid, as measured by a wheat bioassay, was highest in tubers from unfertilized plants. The level of the other, as measured by the intensity of fluorescence under u/v radiation, was highest in tubers with a high of scopoletin, and the observed differences in time of sprouting and the proportion of eyes sprouting explained in terms of the known activity of scopoletin and its glycosides. Sprout growth rate increased and the symptoms of correlative inhibition decreased with increasing tuber N. The differences in the yield produced by the seed tubers were related to seed tuber N rather than stem number per seed tuber, although there was some avidence for a depression in stem number related to high seed tuber K and an increase in branching related to low seed tuber N. The early yield differences were equivalent to an increase in 1 ton per acre on a 6 ton crop.
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