Analysis of Growth and Water Relations of Tomato Fruits in Relation to Air Vapor Pressure Deficit and Plant Fruit Load |
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Authors: | Soraya Guichard Christian Gary Cherubino Leonardi Nadia Bertin |
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Institution: | (1) Institut National de la Recherche Agronomique, Unité Plantes et Systèmes de Culture Horticoles, Domaine St-Paul, Site Agroparc, Avignon CEDEX 9, 84914, France;(2) Dipartimento di OrtoFloroArboricoltura e Tecnologie Agroalimentari, Catania University, Via Valdisavoia 5, Catania, I-95123, Italy |
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Abstract: | The influence of air vapor pressure deficit (VPD) and plant fruit load on the expansion and water relations of young tomato
fruits grown in a glasshouse were evaluated under summer Mediterranean conditions. The contributions of phloem, xylem and
transpiration fluxes to the fruit volume increase were estimated at an hourly scale from the growth curves of intact, heat-girdled
and detached fruits, measured using displacement transducers. High VPD conditions reduced the xylem influx and increased the
fruit transpiration, but hardly affected the phloem influx. Net water accumulation and growth rate were reduced, and a xylem
efflux even occurred during the warmest and driest hours of the day. Changes in xylem flux could be explained by variations
in the gradient of water potential between stem and fruit, due to changes in stem water potential. Misting reduced air VPD
and alleviated the reduction in fruit volume increase through an increase in xylem influx and a decrease in fruit transpiration.
Under low fruit load, the competition for assimilates being likely reduced, the phloem flux to fruits increased, similarly
to the xylem and transpiration fluxes, without any changes in the fruit water potential. However, different diurnal dynamics
among treatments assume variable contributions of turgor and osmotic pressure in F3 and F6 fruits, and hypothetical short-term
variations in the water potential gradient between stem and fruit, preventing xylem efflux in F3 fruits. |
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Keywords: | Tomato Solanum lycopersicon L Water flux Water potential Xylem Phloem Transpiration Fruit growth VPD Plant fruit load Fruit quality |
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