EFFECT OF ROOT TEMPERATURE AND VARYING CATION RATIOS ON GROWTH AND LEAF CATION CONCENTRATION OF APPLE SEEDLINGS GROWN IN NUTRIENT SOLUTION

Abstract

Apple seedlings (Malus domestica Borkh.) were grown at high (256 mg L −1 ) and low 32 mg L −1 ) Ca concentration in Long Ashton nutrient solutions at 8, 12, 16 and 20 °C root temperature. Top and root dry weight of seedlings increased as temperature increased. Leaf Ca, K and Mn concentrations increased with root temperature from 12 to 20 °C. Leaf Zn concentration decreased over the same temperature range at low solution Ca concentration, leaf Mg concentration was lowest at 16 °C while leaf Fe was unaffected by temperature. In further experiments, seedlings were grown at 12 and 16 °C root temperatures at five concentration ratios of Ca:K (4:1, 2:1, 1:1, 1:2 and 1:4) and five concentration ratios of K:Mg (17:1, 10:1,4:1,2:1 and 2:3) in nutrient solution. Seedling growth was higher at 16 °C and varied inversely with K:Mg ratio but was unaffected by Ca:K ratio. Leaf Ca concentration increased with temperature regardless of nutrient solution composition. Leaf K concentration increased with temperature over the range of Ca:K ratios but not over the range of K:Mg ratios. Leaf Mg concentration was unaffected by temperature. These data show that leaf Ca, Mg and K concentration increase in response to their respective availabilities in solution, being most pronounced for Mg and least for Ca.Key words: Apple seedlings, root temperature, nutrient solution, leaf Ca, Mg and K, Malus domestica