Dynamics of mineral nutrients in tomato (Solanum lycopersicum L.) fruits during ripening: part I-on the plant

Tomato (Solanum lycopersicum L.) fruits of 9 popular varieties in India were analyzed for changes in the levels of different nutrients (P, K, Mg, Ca, Fe, Zn, B, Cu and Mn) at 5 different ripening stages. For this, tomato fruits at different ripening stages (immature, green mature, turning, light red and red ripe) were harvested directly from the plant. Nutrients were estimated in the outer pericarp (devoid of internal pericarp, locular tissue and seeds) of the tomato fruits. Transition of tomato fruits from immature stage to green mature stage showed net decrease in the contents of Zn, Ca and Mn while, all other nutrients maintained their levels. Indicating that tomato fruits at green mature stage can have sub-optimum levels of Zn, Ca and Mn. This finding is of academic and practical relevance as tomato fruits are generally harvested at green mature stage for their postharvest storage, transportation and marketing purposes. Further, comparison of different nutrients at green mature stage in different varieties showed varietal variability with respect to K, Fe, Cu, Mg, Ca, and Mn. Implications of this varietal variability are highlighted on postharvest physiology and ripening-related changes in tomato fruits. The trend by different varieties during the course of ripening and also across the varieties (particularly when red ripe stage was compared with green mature stage) showed net increase for P, K and Fe, net decrease for Mg, Ca and Mn and no significant change for Zn, B and Cu. Besides the difference in the mobility of different nutrients in phloem, obtained results are being discussed in view of 1) continuous availability of nutrients to the fruits by the plant, 2) Internal mobilization of nutrients (within the fruit) and 3) Remobilization and backflow of nutrients (away from the fruit to the stronger sinks).