Influence of nitrogen to potassium ratio in the nutrient solution on the formation of leaf apparatus of Batavia-type lettuce hybrids

Abstract

The research findings on the effects of varying nitrogen to potassium ratios in nutrient solutions on leaf development of Batavia lettuce hybrids are discussed. The lettuce plants were grown under controlled microclimate conditions. The night-time air temperature was maintained at 17-20°C, and 19-22°C during daylight hours. Relative humidity in the plant area was 70-75%. Lighting was provided by a combined supplementary lighting system including high-pressure sodium lamps (HPS) and light-emitting diode (LED) light sources. Three mineral nutrition systems on two lettuce varieties were studied: Aficion RZ and Othilie RZ. The nutrient media varied in nitrogen and potassium concentrations and N:K ratios. The T1 nutrition system (N₁₄₀P₄₅K₂₇₀Ca₉₀Mg₅₀S₂₃ mg L), solution conductivity - 1.9 mS cm, N:K ratio - 1:1.9. The T2 nutrition system (N₁₈₀P₄₅K₂₅₀Ca₈₅Mg₅₀S₂₃ mg L), solution conductivity - 2.1 mS cm, N:K ratio - 1:1.4. The T3 nutrition system (N₁₁₅P₄₅K₃₀₀Ca₁₀₀Mg₅₀S₂₃ mg L), solution conductivity - 2.0 mS cm, N:K ratio - 1:2.6. It was found that changing the nutrient ratio had a significant impact on plant morphometric indices. The largest leaf length, lamina width, and leaf surface area in both hybrids were obtained using the T1 nutrient system with an N:K ratio of 1:1.9. It was proved that increasing the potassium content while decreasing nitrogen concentration in the T3 variant (N:K ratio of 1:2.6) resulted in a significant reduction of leaf area and leaf count. The Aficion RZ hybrid was characterized by more intensive development of the assimilation apparatus and greater response to changes in mineral nutrition conditions.