Salinity stress limits plant growth and development and presents a significant obstacle to global food production. A split-root hydroponic system was used to evaluate the salinity tolerance of cherry tomatoes (Solanum lycopersium var. cerasiforme). The objective was to establish a salinity threshold that would increase both crop performance and plant resistance to salinity stress. Three salinity levels: 0 parts per thousand (ppt), 4.5 ppt, and 9 ppt and two root conditions: homogeneous and heterogeneous were used. The split-root system was adopted to expose one side of the root system to saline water and the other side to freshwater conditions.
A randomized complete block design was used, with three replications and a total of 36 experimental units. The size index (plant height, widest width, and perpendicular width), stomatal conductance, photosynthesis rate, fruit production, and chlorophyll content were among the growth and physiological characteristics that were measured. EC, pH, DO, and salinity levels of the treatments were also monitored weekly. Dry shoot and dry root weights were measured, and leaf tissue analysis was done at end of the experiment. The results showed that tomato fruit yield significantly decreased (p<0.05) with increasing salinity levels and that both the shoot dry and the root dry weight was greater in homogeneous mixtures, with the exception of salinity level of 9 ppt. The salinity tolerance threshold was exceeded in the 9 ppt homogeneous treatment, resulting in lower dry root and shoot dry weights compared to the 9 ppt heterogenous treatment.
The stomatal conductance decreased throughout the day with increasing salinity levels as the increased salt stress triggered stomata closures in the tomato leaves, reduction in the CO2 intake and reduction in the plant photosynthetic rate. Salinity also increased the EC of the solutions and the foliar analysis results showed reduction in the nutrient uptake and foliar nutrient concentration in the 4 ppt and 9 ppt treatments. The results show that utilizing the split-root technique can increase cherry tomato salinity tolerance. Future research will concentrate on using different tomato cultivars, using shrimp water effluent, and investigating the implications for the timing of salinity stress on the cherry tomatoes.