The Development of Tomato Root System in Relation to the Carbohydrate Status of the Whole Plant

The decrease in growth rate of the root system or complete cessationof its growth in developed, fruit-bearing tomato plants areknown phenomena. It has been suggested that a limited supplyof carbohydrates to this organ, due to its relative weaknessin competition with the flowers and developing fruitlets isthe main cause for these disorders. This theory was tested inthe present study with plants grown in an aerohydroponic systemup to the appearance of 12–13 trusses per plant, 172 dafter transplanting. The changes in the contents of carbohydratesin the various organs during this period were monitored. Theconcentrations of soluble sugars and starch in the leaves increasedwith the increase in truss number. The upper stem was foundto contain more carbohydrates than the lower stem, while nosignificant changes in the concentration of these compoundscould be detected in the roots throughout the experiment. Nevertheless,120–130 d after transplanting, the roots of the plants,bearing five to six trusses and two to three inflorescences,ceased growing and remained at the same or a slightly reducedsize for another 40–50 d. Calculations show that at thestage of five to six trusses, 38 g total soluble sugars and35 g starch were stored in the vegetative organs. Therefore,it seems unlikely that carbon deficiency caused by the competitionwith the reproductive organs (mainly developing fruits), affectedthe root growth. Instead, it is suggested that some other factoris responsible. Lycopersicon esculentumMill; carbohydrates; root growth rate; sink-source relationship; soluble sugars; starch