A study of the effect of water stress on the yield, physico-chemical characteristics and nutrient up take of solanum lycopersicum L.
This study investigated the osmotic adjustment and nutrient uptake of six varieties of tomato (Solanum lycopersicum L.) at different watering regimes and evaluated the relationship between water stress and marketable yield of the tomato varieties. This was with a view to determining the role of water in crop growth and production. The six varieties of Solanum lycopersicum used for the study were: Chico III, Ibadan local, Ibarapa, Ife-1, Rio Grande and Roma-VFwere the tomato varieties collected from the National Horticultural Research Institute (NIHORT), Ibadan, Oyo State, Nigeria.The tomato seed varieties were sown in bowls of 54 cm x 8 cm dimension and the seedlings were transplanted after 21 days of establishment into 54 experimental pots (20 cm x 21 cm) at the rate of three seedlings per pot. The seedlings were raised in a screenhouse under normal environmental conditions. The experimental layout was quantified with three levels of watering regimes (W1, W3 and W5). A 6 x 3 factorial experiment laid out in a completelyrandomised design (CRD) was used; with watering regimes and varieties as the factors. Samplings were carried out after three weeks of transplanting. Data were recorded for growth, yield and yield components. The parameters studied for osmotic adjustment were relative water content (%) and proline (µmolg-1). Sodium, potassium, magnesium, calcium and manganese contents were analysed after digestion using Perkin Elmer Analyst Model – 400 Atomic Absorption Spectrophotometer. The proximate composition and the physico-chemical properties of the tomato varieties were carried out using standard procedures. Data were subjected to analysis of variance (ANOVA) while the means were separated using least significant difference (LSD) post-hoc at p ≥0.05 level of probability. Tomato plants subjected to water stress were reduced significantly (p ≥0.05) in their shoot height, number of leaves and plant biomass compared to those that were watered everyday. Accumulation of proline enhanced water stress tolerance in tomato varieties of Ibadan local and Ibarapa, by improving the osmotic adjustment of the varieties, while the high relative water content in the Chico III and Roma-VF varieties made them more drought tolerant. The highest uptake of sodium, magnesium, calcium and manganese were enhanced by drought condition in Ife-1, Ibarapa and Roma-VF varieties, while,the highest uptake of potassium was influenced by watering everyday. Better fruit yield was obtained with three days watering regime. However, 35 % and 104 % reduction in yield respectively occurred with watering everyday and watering every five days. Tomato plants watered every five days had the best accumulated levels of proteins, carbohydrate and dry matter, while the plants watered every three days had the best moisture, fat and ash contents. A considerable range of variation was recorded among the tomato varieties and the drought tolerance of the varieties were in the order: Ife-1 = Chico III > Ibadan local = Roma-VF > Rio Grande > Ibarapa. The study concluded that the accumulation of proline could not be used as the sole determinant of osmotic adjustment in water stressed plant but also potassium and magnesium ions uptake.