POTENTIAL DRY-MATTER AND WATER IMPORT RATES IN THE TOMATO FRUIT IN RELATIONSHIP TO FRUIT SIZE

The tomato fruit was compared to a sphere with a radius R. Radial growth rates in the fruit (F1%v and FID) due to water import or to dry matter import, respectively, which are also the water import rate or dry matter import rate per unit surface area of fruit, were calculated from two sets of published results. This data referred to fruits which swelled in such a way that the availability of assimilates had little effect on growth. Two varieties differentiated the two series of results and in one series, three trials were differentiated by the salinity of the nutrient solution.In all trials, it was found that Flv and Fm decreased when R increased. Two phases were observed for F1W: after a first phase, Fiyf decreased more quickly and almost linearly when R increased. Fm was constant or decreased with respect to R. Except at the beginning of growth at the greatest salinity, there were clearly linear regressions between F1W and FjD such as Fm = aFiW — b: where b was lower with higher salinity. The changes of the concentration of imported dry matter (FID//yw) were examined in terms of R and FlVf/R. The mechanisms controlling the changes in FIV/and FlD were discussed. The results suggested fruit radius was an important parameter of these mechanisms. Thus, water import rate and dry matter import rate could each be considered to be the product of two factors: fruit surface area, which is directly dependent on fruit radius, and water import rate or dry matter import rate per unit of fruit surface area. © 1993 Annals of Botany Company.