title: High light decreases xylem contribution to fruit growth in tomato.
abstract: Recently, contradicting evidence has been reported on the contribution of xylem and phloem influx into tomato fruits, urging the need for a better understanding of the mechanisms involved in fruit growth. So far, little research has been performed on quantifying the effect of light intensity on the different contributors to the fruit water balance. However, as light intensity affects both transpiration and photosynthesis, it might be expected to induce important changes in the fruit water balance. In this study, tomato plants (Solanum lycopersicum L.) were grown in light and shade conditions and the fruit water balance was studied by measuring fruit growth of girdled and intact fruits with linear variable displacement transducers combined with a model-based approach. Results indicated that the relative xylem contribution significantly increased when shading lowered light intensity. This resulted from both a higher xylem influx and a lower phloem influx during the daytime. Plants from the shade treatment were able to maintain a stronger gradient in total water potential between stem and fruits during daytime, thereby promoting xylem influx. It appeared that the xylem pathway was still functional at 35 days after anthesis and that relative xylem contribution was strongly affected by environmental conditions.
authors.affiliation: Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000, Gent, Belgium.
authors.forename: Jochen
authors.initials: J
authors.lastname: Hanssens
authors.forename: Tom
authors.initials: T
authors.lastname: DE Swaef
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
mesh_terms: D005638:Fruit / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects*; D008027:Light; D018551:Solanum lycopersicum / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects*; D052585:Phloem / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects*; D018547:Plant Stems / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000528:radiation effects*; D014867:Water / Q000502:physiology; D052584:Xylem / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects
chemical_list: D014867:Water
keywords: Solanum lycopersicum L.; dendrometers; girdling; heat field deformation (HFD) sensor; irradiance; mechanistic modelling; phloem; water flux; water potential; water status