Changes in fruit-source ratio during the growth and maturation of cherry tomato fruits were studied in combination with increased fruit temperature. Six treatments were compared: the presence or absence of local heating combined with different fruit origins (7P, fruit from trusses pruned to seven flowers; 14P, proximal fruits; 14D, distal fruits from trusses pruned to 14 flowers). 7P were less sensitive to heating whereas 14P and 14D showed greater reduction in water and dry matter (DM) content. Distal fruits had the lowest structural DM (sDM), which could be due to a lower fruit cell number. Heating further decreased the sDM, so that fruit sink size was the lowest for distal fruits subjected to heating. Under low competition (7P), heating had a beneficial effect on sugar and lycopene content, whereas acids, β-carotene and vitamin C content were reduced. Under high competition (14P, 14D), heating increased the ratio sDM-DM. This was mainly due to the reduced content of sugars and acids, but also to the reduced accumulation of secondary metabolites such as vitamin C, β-carotene and lycopene. This study underlines the interactions between fruit temperature and the fruit-source ratio and the consequences for fruit composition and nutritional quality.

M. 2005. Effect of photoselective filters on the physical and chemical traits of vine-ripened tomato fruits. Can. J. Plant Sci. 85: 439-446. The effects of several wavelength selective light filters placed on developing mature green tomato fruits were studied to determine whether light environment during fruit ripening has an impact on fruit composition. Juice titratable acidity and fruit fresh and dry weight varied little with the different filters. Reducing the red/far-red light ratio with a green filter to simulate vegetation shade slightly delayed ripening. Reducing infrared light (700-1100 nm) reduced vitamin C and soluble sugars content. A drastic reduction in photosynthetic light (97%) reduced both β-carotene (-23%) and lycopene (-29%) contents and red coloration (-21%). Significant correlations were found among the content of soluble sugars, vitamin C and lycopene, but these components increased differently according to the spectral composition of the light transmitted to the fruit. The content of lycopene and β-carotene increased with exposure to photosynthetic radiation and more precisely with exposure to blue light. In contrast, the content of vitamin C and sugar increased with infrared light exposure. . L'effet de filtres sélectifs de différentes longueurs d'onde placés sur des fruits de tomate verts en maturation est étudié afin de déterminer si l'environnement lumineux durant la maturation des fruits influence leur composition. L'acidité titrable du jus et le poids frais et le poids sec sont peu modifiés par les différents filtres. La diminution du rapport rouge clair / rouge sombre avec un filtre vert simulant l'ombrage par la végé-tation retarde légèrement le mûrissement. Une diminution du rayonnement dans le proche infra-rouge (700-1100 nm) diminue la teneur en vitamine C et en sucres solubles. Une diminution importante du rayonnement photosynthétique (97%) diminue à la fois les teneurs en β-carotène (23%), lycopène (29%) et la coloration rouge des fruits (21%). Les teneurs en sucres solubles, vitamine C, et lycopène sont corrélées mais augmentent différemment selon la composition spectrale du rayonnement transmis au fruit. Les teneurs en lycopène et en β-carotène augmentent avec le rayonnement photosynthétique arrivant au fruit et plus particulièrement avec la quantité de lumière bleue. Par contre les teneurs en vitamine C et en sucres augmentent avec le rayonnement infra-rouge.

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