The Effects on Yield and Some Physio–Morphological Traits of Different Salinity and Potassium Treatments in Lettuce

This study was conducted to determine effects on yield and some physicological (relative water content, stomatal conductance and membrane leakage) and morphological (plant height and diameter, total and thrown leaves) traits of lettuce plant at different salinity and potassium levels in the winter period in 2011–2012 under greenhouse conditions. Two different salinity (0.6 dS m-1 (T0) and 4.0 dS m-1 (T1)) and four different potassium levels (5 kg da-1 (K1), 16 kg da-1 (K2), 32 kg da-1 (K3) and 48 kg da-1 (K4)) were applied in this research. As a result of the study, It was seen that the yield of lettuce was affected significantly by salinity irrigation water and the increase in potassium level applied had not a positive effect on yield. The yield and physiological traits reduced because of much more potassium application than necessary under non–salinity conditions. Potassium did not affect the yield and only membrane leakage from physiological traits under salinity conditions. The highest stomatal conductance and relative water content values were obtained from treatments applicated much more potassium than necessary in lettuce irrigated by both non–salinity and salinity water. It was seen that plant height and leaf number from morphological traits did not change by increase or decrease of salinity and potassium levels. As a result, it was seen that increasing of salt levels affected negatively plant growth, and applying of much more potassium than necessary did not reduce the salinity stress.