ECOPHYSIOLOGICAL RESPONSES OF Solanum lycopersicum L. cv RIO GRANDE TO IRRIGATION AND SALINITY REGIMES IN SCREENHOUSE

Increasing population, a rapidly changing climate and declining arable land necessitates knowledge on performance of high valued crops under predicted abiotic stress conditions. Water and salinity stress will dominate future crop production environments. We investigated the effect of three irrigation levels comprising a deficit and an excess irrigation scenario, and four salinity levels of 0, 4, 8 and 12 ppt in a 3x4 factorial design, on the growth, yield and ecophysiological attributes of tomato in screenhouse. Measurements were taken till maturity and data subjected to GLM ANOVA, Spearman Rank Correlation and Factor analyses. Increasing salinity from 0 to 8 ppt significantly decreased the mean number of leaves from 56.02 to 50.64, and leaf area from 1008 to 874 cm2. Senescence was more at higher salinity. For all salinity levels, transpiration rate per plant were higher for higher irrigation water volumes. Over time, plants irrigated with 4.5 L of water per week transpired more water across all salinity levels with the highest (0.19 L) observed at 8 ppt. Increased irrigation resulted in a higher transpiration rate. Salinity increase from 0 to 12 ppt significantly increased succulence from 2.08 to 5.23, while SMF decreased significantly from 0.8 to 0.55. An increase in irrigation resulted in a mean decrease in WUE from 5.27 to 1.61gl-1 and a mean decrease in TUE from 516.2 to 148.05gl-1, while transpiration rate increased for the same irrigation intervals. Therefore tomato is more susceptible to salinity than water stress, and its output will reduce under future saline soil conditions.