Exogenous sucrose and invertase application enhanced reproductive heat stress tolerance in tomato

Heat stress inhibits invertase activity and reduces sucrose transport to reproductive organs in tomato ( Solanum lycopersicum L.), resulting in insufficient carbon supply for optimal flower and fruit development. This study evaluated the effects of sucrose and invertase applications on enhancing heat stress tolerance of tomato plants. ‘Micro-Tom’ plants were grown in 2-L pots filled with growing media and subjected to optimal (26/19°C) or heat stress (33/26°C) conditions in a growth chamber (16/8 h day/night). Treatments included foliar spray or floral dip with 1% ( w/v ) sucrose or 300 U/L invertase solutions, applied every three days during the flowering stage. Foliar invertase application enhanced pollen (22.7%) and ovule (11.4%) viability under heat stress, possibly due to increased starch utilization compared to control plants. The increased leaf invertase activity also led to higher total soluble solids (TSS) and β-carotene concentrations in fruits by 9.9% and 46.3%, respectively. Similarly, floral invertase treatment improved pollen viability (17.9%) and fruit TSS (8.8%). On the other hand, foliar sucrose application increased ovule number (20.7%) and viability (12.3%) under heat stress, resulting in a 34.3% higher fruit set. Floral sucrose application also improved ovule viability (11.7%) under heat stress. However, no significant yield differences were observed among treatments. In conclusion, exogenous sucrose and invertase applications enhanced the thermotolerance of flowering organs by improving pollen and ovule viability, while these physiological benefits were not fully translated into yield or fruit quality improvements.