Tropentag, September 10 - 12, 2025, Bonn "Reconciling land system changes with planetary health"

Interactive effects of vpd and salinity on growth, ion distribution, and tolerance thresholds in hydroponically grown tomato

¹University of Hohenheim, Inst. of Agric. Sci. in the Tropics (Hans-Ruthenberg-Institute), Germany
²University of Hohenheim, Inst. of Agric. Sci. in the Tropics (Hans-Ruthenberg-Institute), Germany
³University of Hohenheim, Inst. of Agric. Sci. in the Tropics (Hans-Ruthenberg-Institute), Germany

Abstract

Root zone salinity and VPD significantly impact crop growth and yield. Adapting crop production to climate change requires a clear understanding of how these factors interact, enabling the development of resilient agricultural practices essential for sustaining food security.
Two varieties of Solanum lycopersicum L. (cv’s Saluoso, Sweeterno) were grown hydroponically under high (3.2 kPa) and low (0.7 kPa) VPD at three levels of root zone salinity namely 0, 40 and 80 mM NaCl. Leaf area, evapotranspiration, plant height, leaf number, and stem diameter were recorded. Dry weights were measured for all plants, with biomass partitioned into leaf blades, petioles, structural parts (petiolule and rachis), stems, and roots. Ion contents (Na⁺, Cl^- and K+) were analysed in all partitions.
Under high VPD, salinity reduced total biomass in Saluoso by 38% and 95%, and in Sweeterno by 32% and 87% at 40 mM and 80 mM NaCl, respectively. In contrast, at low VPD, 40 mM NaCl led to a biomass increase in Saluoso by 10% and in Sweeterno by 32%. However, at 80 mM NaCl, biomass decreased significantly in both cultivars under both VPD regimes. Salinity thresholds were cultivar and VPD specific: Under high VPD, biomass reduction began at 17 mM NaCl in Sweeterno and at just 12 mM in Saluoso. In contrast, under low VPD conditions, Sweeterno tolerated up to 52 mM NaCl and Saluoso up to 44 mM before showing significant reductions in growth. These thresholds highlight the stronger resilience of Sweeterno across salinity and VPD. High VPD enhanced leaf area and biomass accumulation at 0 mM mM NaCl, but these benefits diminished as salinity increased, becoming negligible at 80 mM NaCl.
The relationship between ion uptake and distribution in the plant and the positive effects of high VPD on biomass formation and leaf area are be discussed.

Keywords: Dry weight, Hydroponics, Leaf area, salinity, Threshold, Tomato, Vapor Pressure Deficit (VPD)

Contact Address: Hemanth Kumar Puppala, University of Hohenheim, Inst. of Agric. Sci. in the Tropics (Hans-Ruthenberg-Institute), Garbenstrasse 13, 70599 Stuttgart, Germany, e-mail: hemanth.puppalauni-hohenheim.de