Effects of fruit characteristics and climatic conditions on tomato transpiration in a greenhouse

Experimental data of the transpiration and surface temperature of detached tomato fruits were collected to study and analyse how tomato fruit transpir ation (E) was related to fruit characteristics, growth stage and climatic c onditions. The measurements were carried out (i) in controlled conditions o n fruits weighing between 10 and 140 g and (ii) during several summer days on fruits of 60-100 g under two greenhouse compartments with contrasted thi gh and low levels of air vapour pressure difference (VPDa). The transpirati on rate, when expressed on a fruit area basis (g cm(-2) h(-1)), showed only a very slight dependence upon weight. Linear models relating E in unit are a to (i) VPA(a) and (ii) VPD(fr-a) (fruit-to-air vapour pressure difference ) by means of a total conductance to water vapour (g(t)), were proposed and their parameters were identified for fruits grown under the high and low V PD regimes. These models were able to explain a significant part of the obs erved variation in fruit transpiration. The parameters of the model differe d with respect to growth conditions. The results evidenced the role of both fruit characteristics and climatic conditions on fruit transpiration and t hat the response of fruit transpiration to VPD could be separated into two components: (i) a short-term and reversible response which seems to be rela ted to instantaneous changes in cuticular hydration linked to the prevailin g VPD conditions and (ii) a long-term and irreversible response due to cuti cle characteristics which depend on the average lever of VPD experienced by the fruit during its growth.