From the results, and from observations made in the field, it is possible to form a picture of the after-effects of various storage conditions, and the following conclusions are derived:
1. Low temperature storage (40°P), F), and TCNB application can be used successfully to prolong the dormant period. Crops from seed stored at either conditions were similar in growth and yield of tubers of all grades.
2. Temperature and light are the most important controlling factors in the growth of sprouts, a change in either of these factors can suddenly change the growth of sprouts. High temperature in bright light gives reasonably short sprouts, while high temperature in darkness causes long etiolated sprouts.
3. The time at which shitting takes place, controls the number of sprouts per seed tuber. Seed tubers, when chitted immediately after lifting produce one (or sometimes 2 to 3) dominant sprout, usually on the apical region (apical dominance phase). When they are shitted at later dates, apical dominance gradually disappears and the number of sprouts per seed tuber increases (multiple sprouting phase).
4. There was no evidence that a short period of heat treatment (65-70°F for 10 days) during the storage period of seed tubers, did anything to break apical dominance.
5. Tubers with one sprout produce fewer tubers per hill than those with multiple sprouts, and those unsprouted, but result in a greater number of tubers per main-stem presumably due to the development of more nodes per dominant sprout and also to less competition among the tubers for plant food.
6. There was no evidence that there is any yield advantage from sprouted seed as compared with unsprouted seed, provided plants from both are allowed to reach maturity. The results do suggest, however, that unsprouted seed produce a crop with a larger number of tubers than sprouted seed. From this there seems to be considerable merit in planting unsprouted seed tubers where a seed crop is desired. It should also be stressed that early planting of unsprouted seed is desirable.
7. Plants from sprouted tubers emerge, flower, and tuberize about 10-15 days earlier than those stored at low temperature or treated with TCNB for the whole storage period.
8. Desprouting seed tubers of the variety Arran. Pilot results in a crop with a significantly higher number of tubers. With this variety, therefore, there would seem to be some advantage, for seed potatoes, in planting unsprouted tubers which have lost sprouts during the riddling process, before planting.
9. There was some evidence that seed tubers kept under chitting conditions (60 -65 °F) for a longer period (thus producing longer sprouts) produced plants with fewer tubers than seed shitted at the same time, but transferred to cool conditions (f" 40 °F) earlier (when sprouts 1 cm. long), Further corroboration of this is required.
10. In all the comparisons the number of main -stems per hill was directly proportional to the number of tubers produced per hill, but the number of main -stems per hill was inversely proportional to the number of tubers per main - stem, i.e. a hill with fewer main -stems produced more tubers per main- stem than a hill with more main- stems.
11. The effect of large seed and close spacing in producing a larger population of main -stems and tubers per acre was corroborated in this work. The yield and the number of seed sized tubers also increased significantly, while there was a decrease in the yield and number of ware -sized tubers,