End of Project Report The Effect of Planting Density on the Production Of Potato Minitubers Under Protection: Micropropagation of potatoes can be used to bulk up stocks of new cultivars or disease free stocks of existing cultivars. Rooted microplants are grown under protection to produce minitubers which undergo multiplication over a number of generations to produce seed potatoes. The object of these experiments, undertaken for Dubcap Ltd., was to study the effect of planting density on minituber production under greenhouse conditions. They were also designed to serve as a basis for assessing the feasibility for recycling minitubers especially small (8-15 mm) ones which have been shown not to perform satisfactorily under field conditions. The experimental system was designed to serve as a prototype for a commercial operation which would function as a satellite production site remote from the tissue culture laboratory. Development Of A Growing Medium Based On Forest Tree Bark: The aim of these experiments was to develop a plant growing medium based on 100% Sitka spruce bark through first studying the effect of rate of application and source of nitrogen on the composting of milled sitka spruce bark and then optimising the nutrient addition to the composted bark.