THE EFFECT OF SOME ENVIRONMENTAL-FACTORS ON POTATO-TUBER NUMBERS

Five experiments studied the effects of shading, temperature and stole n growth medium on stolen and tuber formation. The lowest numbers of s tolons and tubers were produced at the higher and lower nodes. Numbers of primary stolons and tubers were relatively stable across nodes and treatments and variation in total numbers was largely due to changes in numbers of lateral and branch stolons. In the field, 70% shading re duced numbers of stolons and tubers by reducing lateral and branch sto lons, while in hydroponics, 45% shading and temperatures at initiation had no effect on tuber numbers. In both environments later planting t ended to reduce numbers of stolons and tubers. There were large effect s of the physical environment, with compost producing three times as m any tubers as dry vermiculite. The potential number of tubers may be d etermined by the number of stolons and the environmental conditions af fecting stolen formation and development.