Potassium Affects the Lycopene and β-Carotene Concentration in Greenhouse Tomato

The goal of this research was to determine the influence of potassium concentration in nutrient solution on the quality of tomato fruits. Potassium can improve the quality of tomato by influencing carotenoid synthesis. Two experiments with 'Gabriela' hybrid were carried out in an intermediate level technology greenhouse system in soilless culture. A standard nutrient solution was applied to the plants in the vegetative stage (VS) and different solutions with different potassium (K) concentrations were applied to the plants in the reproductive stage (RS1 (20% K), RS2 (40% K), RS3 (60% K), and RS4 (45% K)); the percentage of K referred to the percentage of total cations as K. All nutrient solutions had 30 mg L-1 of total ion concentration, pH 6.5, and EC of approximately 3 dS m(-1). In the first experiment, three treatments (RS1, RS2 and RS3) with eight replicates were tested. In the second experiment, two treatments (RS2 and RS4) were used with 16 replicates. The RS4 treatment surpassed significantly to RS2 in all fruit quality parameters, except for beta-carotene and pH for each one of selected tomato fruit clusters (1(st), 3(rd), 5(th), 7(th) and 9(th)). The concentration of potassium affected the concentration of nutraceuticals, such as lycopene and beta-carotene, which can be used as indicators for tomato quality. This study suggested that it is possible and feasible to produce high quality tomato in "the Bajio Guanajuatense" region of Mexico with economically accessible intermediate technology; nevertheless, the management modifications will have to be considered.