Optimum range in potato tubers grown under plastic mulches: III Quality and physiological indices and parameters

For 3 years (1993-1995) Solanum tuberosum L. var. Spunta. was grown under d ifferent polyethylene [PE] sheets: (25 mu-thick, transparent PE, (T-1), 25 mu-thick, white PE, (T-2); 50 mu thick-coextruded black-and-white PE (T-3); 25 mu-thick black PE, (T-4); controls (not covered, (T-0). We determined the optimum range of non-structural carbohydrates, proline, a nd ionic balance together with related ratios. We also determined physiolog ical indices (Alcaline Index, Fe Index and Vegetative Index) and physiologi cal ternary groups of soluble and total macro and micronutrients.