Fruiting of tomato cultivated on medium enriched with bicarbonate

The incorporation of bicarbonate (HCO3) by roots and the transport of its products to plant tops significantly affected the yield of tomato. Fresh weight of fruit exceeded the control by 32.6% on average. The result was parallel associated with fruit ripening which began by 10 days earlier and also with the final phase of this process shortened by five days. Changes were determined in the content of individual sugars [glucose (G), fructose (F), and sucrose] and organic acids [malic (MA) and citric (CA)] in the outer wall of pericarp and in the locular tissue. As compared with the control, in the series with HCO3 (series II) the content of G+F increased by about 34% and 46% in the wall and by 23% and 30% in the locular tissue of mature green and red stage, respectively. Distribution of G and F in the wall and locule was 3:1 in the control at the mature green phase and fell to 2.2:1 as the fruit ripened. In series II this ratio was similar for the two kinds of tissue, being 3.3:1 and 2.2:1. Moreover, the G/F ratio indicates an increased level of F in red ripe fruits of series U, being about 1 and 0.86 in the wall and 0.86 and 0.75 in the locular tissue in the control and series II, respectively. The content of sucrose was low and similar in the tissues of the two series. In red ripe fruits sucrose constituted about 0.2% of the total concentration of sugars. In fruit of series U the accumulation of organic acids exceeded the control by about 27% - 36%. The MA/CA ratio in mature green had the value >1 in the wall (1.11 and 1.21 in the control and series II, respectively) and <1 in the locule (0.75 and 0.81, respectively). In red stages its value was lowered in two kinds of the tissue (in the wall <1). Sugars/organic acids ratio increased during ripening, confirming the occurrence of rapid metabolic changes of organic acids in this period. The F/CA ratio that is responsible of sweetness and sourness to greater degree than G and MA, was higher in the walls of fruit in series II by about 0.3 unit. The above data show that an increase in HCO3 content in root environment might be an important factor increasing yields in glasshouse tomato cultivation.