EFFECT OF ADDING HEATING PIPES ON THE TEMPERATURE AND THE PHYSICAL AND CHEMICAL TRAITS OF TOMATO FRUITS

The effect of adding heating pipes near growing fruits of cherry tomato was studied on truss 5 throughout fruit development. Leaves and fruits close to heating pipes showed 1 to 1.5°C increased temperature both during day and night. Fruit firmness was not modified but fruit fresh weight was significantly reduced by heating from 4% to 12% depending on the source / sink ratio. Fruits harvested on plant where trusses were pruned to 7 flowers were less sensitive to heating whereas fruits harvested on plant where trusses were pruned to 14 fruits showed greater reduction in water and dry matter (DM) content. Beyond these fruits, tip fruits which have the lowest sink strength were more sensitive to heating than basal fruits. Under low source / sink ratio, DM content was reduced by heating but the proportion of structural dry matter (sDM) to total DM increased. This was mainly due to the reduced content of sugars and acids. In addition, heating also greatly reduced the accumulation of secondary metabolites such as vitamin C and -carotene, whereas lycopene was less reduced (except for tip fruits). We conclude that whatever the truss pruning, heating will reduce the fruit content in some specific compounds such as vitamin C, and -carotene and consequently affect fruit quality.