Foliar application of isosorbide influences fruit fresh weight in Micro-Tom tomato

Isosorbide, a bicyclic sugar alcohol, has recently been reported to exhibit potential plant biostimulant activity in Arabidopsis thaliana [2]. However, whether these effects extend to crop plants, particularly in terms of growth and yield, remains unclear. In the present study, we evaluated the effects of foliar-applied isosorbide on fruit production in tomato (Solanum lycopersicum cv. Micro-Tom). Foliar application of isosorbide (2.5 mM) was performed at the flowering stage under once-weekly and twice-weekly spray regimes. At maturity, fruit fresh weight, mean individual fruit fresh weight, fruit number, and total soluble solids (Brix %) were measured. Once-weekly isosorbide foliar application significantly increased total fruit fresh weight and mean individual fruit fresh weight per plant, whereas twice-weekly application did not produce a significant increase. Two-way analysis of variance revealed significant effects of isosorbide treatment and application frequency, as well as a significant treatment × frequency interaction, indicating that the response to isosorbide depended on application frequency. Fruit number was not significantly affected by isosorbide treatment or application frequency, and no significant pairwise differences in Brix were detected among the treatment combinations. These results provide preliminary evidence that foliar-applied isosorbide can influence fruit biomass production in tomato and support further investigation of its potential as a plant biostimulant.