Impact of Salinity on Sugar Composition and Partitioning in Relation to Flower Fertility in Solanum lycopersicum and Solanum chilense

Salinity negatively affects flower production and fertility in tomato but the underlying mechanisms are not fully understood. One hypothesis is that salinity affects sugar partitioning by reducing photosynthesis, which in turn affects source–sink relationships and hence the development of reproductive structures. This study investigates how salt stress alters sugar composition in leaves, flowers, and phloem sap of Solanum lycopersicum and its halophyte relative Solanum chilense, and how this may explain the effects on flower production and fertility. Salt stress increased flower abortion and reduced sepal length in S. lycopersicum, while decreasing pollen grain number in S. chilense. Photosynthetic nitrogen use efficiency was also reduced in S. lycopersicum. Salinity raised myo-inositol and sucrose concentrations in S. lycopersicum leaves but only slightly altered sugar concentrations in flowers. The concentration of sucrose in the foliar exudates was higher in S. chilense as compared to S. lycopersicum, suggesting a higher export of sucrose from the leaves. These findings suggest that S. lycopersicum maintains better metabolic function under salt stress, while S. chilense sustains sugar import to sink organs. Correlations between reproductive traits and sugar dynamics indicate that sugar distribution contributes to reproductive development under salinity stress.